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NUT carcinoma is a rare, aggressive malignancy defined as a carcinoma with a chromosomal rearrangement affecting the nuclear protein in testis ( NUTM1 ) gene. This small round blue cell tumor classically exhibits focal abrupt keratinization and immunohistochemical positivity for keratin and squamous markers. However, keratinization is not always present and reports of positivity for other markers that may obscure the diagnosis are increasing. It is also noteworthy that gene fusions involving NUTM1 are not restricted to NUT carcinoma. Herein, we report a NUT carcinoma arising in the mediastinum of a male patient in his 40 s with morphological and immunohistochemical overlap with Ewing family sarcoma and poorly differentiated synovial sarcoma given a round cell morphology, diffuse strong immunoreactivity for CD99, and patchy strong immunoreactivity for TLE1. Squamous differentiation by morphology and p40 expression were notably absent in this case. Classification as NUT carcinoma was ultimately possible when the morphological and immunohistochemical findings were considered in the context of a BRD4::NUTM1 gene fusion identified by next-generation sequencing. While the patient initially responded to palliative radiotherapy, he died approximately one month later. To our knowledge, this is the first report of TLE1 immunoreactivity in NUT carcinoma. This case highlights a potential diagnostic pitfall and emphasizes the need for molecular confirmation in equivocal situations., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Selective RET inhibitors have shown promise in thyroid cancer (TC) and nonsmall cell lung cancer (NSCLC) harboring RET fusions on next-generation sequencing (NGS), although rarity of the rearrangement has led to limited data for certain tumor types, such as carcinoma of unknown primary. We present a 65-year-old female with no history of malignancy, smoking or radiation exposure, who was found to have an anterior mediastinum malignancy of unknown primary, with metastases to supraclavicular lymph nodes. Core biopsy of the mediastinum revealed poorly differentiated carcinoma, while a biopsy of the thyroid revealed atypia of indeterminate significance (Bethesda III). PD-L1 immunohistochemistry was positive (90%), and liquid NGS revealed mutations in TP53 and the TERT promoter (c.-124C>T), as well as a CCDC6-RET fusion. This genetic profile resembled an anaplastic TC vs. NSCLC primary, although thymic primary and poorly differentiated TC remained on the differential. The patient was initiated on selpercatinib, which was held after 3 weeks due to thrombocytopenia and hypertension. At a reduced dosage, patient developed transaminitis, and selpercatinib was switched to pralsetinib. Brain MRI showed a nonenhancing temporal lobe signal abnormality, which on biopsy proved to be glioblastoma (GBM) with TERT promoter c.-124C>T mutation and FGFR3-TACC3 fusion by NGS. Pralsetinib was held during adjuvant chemoradiation for the GBM, and again for 4 weeks due to pneumonitis that resolved with steroids, and pralsetinib was restarted at a reduced dose. The patient has since demonstrated a stable reduction of the mediastinal mass for >15 months with RET inhibition therapy, despite several treatment interruptions., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Melanoma can pose a significant diagnostic challenge due to the high variability in histological morphology and expression of non-melanocytic immunomarkers. We present a case of a 47-year-old male with an aggressive mediastinal neoplasm and disseminated disease posing several diagnostic challenges. Multiple biopsies were submitted from different anatomic locations and during multiple time points showing an undifferentiated round cell tumor (URCT) with synovial sarcoma-like immunophenotype. SS18::SSX fusion was sought through NGS study for diagnostic confirmation. NGS results revealed NRAS and CDKN2A mutations and absence of fusions, resulting in a new review of the histologic material with a broader immunohistochemical panel, finding strong positivity to melanic antibodies. This case is an illustrative example of a malignant melanoma with small round cell morphology showing aberrant expression of CD99, BCL2, TLE1 and SS18-SSX antibodies exposing a potentially hazardous pitfall highlighting the importance of a wide differential diagnosis and the role of confirmational studies with molecular tests., Competing Interests: Declaration of Competing Interest All authors declare that he/she has no potential conflicts of interest., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

Extragonadal germ cell tumors (EGCTs) are rare, representing <5% of all germ cell tumors (GCTs). Whilst EGCTs share morphological and immunohistochemical features with their gonadal counterparts, they tend to be more aggressive and are frequently associated with secondary somatic malignancies. The aim of our study was to evaluate the clinical, morphological and immunohistochemical features, and to analyze tumors for chromosomal abnormalities of 12p, in addition to any novel genetic alterations, in a series of EGCTs. Seventy-seven EGCTs were included. Anterior mediastinum was the most common anatomic site, followed by central nervous system, retroperitoneum, sacroccygeal area, and neck. Whole genome SNP array identified isochromosome 12p in 26% of tumors. Additional cytogenetic abnormalities included the presence of gain of chr 21 in 37% of tumors. Somatic-type malignancies were identified in 8% of patients. Disease progression (metastasis and/or recurrence) was documented in 8 patients, most of whom died from their relapse. Three patients who died of disease had somatic-type malignancies. Mediastinal seminomas had a significantly better overall survival when compared to mediastinal non-seminomatous GCTs. Our study demonstrates that EGCTs share similar histologic features, but diverse clinical outcomes compared to their gonadal counterparts. Outcomes vary according to anatomic location and histologic subtypes. Our data corroborate that somatic-type malignancies are frequently encountered in mediastinal EGCTs and that their presence portends a poorer prognosis., Competing Interests: Declaration of competing interest None of the authors has any conflicts of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Primary mediastinal B-cell lymphoma (PMBL) and classical Hodgkin lymphoma (cHL) are distinct hematological malignancies of B-cell origin that share many biological, molecular, and clinical characteristics. In particular, the JAK/STAT signaling pathway is a driver of tumor development due to multiple recurrent mutations, particularly in STAT6. Furthermore, the XPO1 gene that encodes exportin 1 (XPO1) shows a frequent point mutation (E571K) resulting in an altered export of hundreds of cargo proteins, which may impact the success of future therapies in PMBL and cHL. Therefore, targeted therapies have been envisioned for these signaling pathways and mutations., Methods: To identify novel molecular targets that could overcome the treatment resistance that occurs in PMBL and cHL patients, we have explored the efficacy of a first-in-class HSP110 inhibitor (iHSP110-33) alone and in combination with selinexor, a XPO1 specific inhibitor, both in vitro and in vivo., Results: We show that iHSP110-33 decreased the survival of several PMBL and cHL cell lines and the size of tumor xenografts. We demonstrate that HSP110 is a cargo of XPO1 wt as well as of XPO1 E571K . Using immunoprecipitation, proximity ligation, thermophoresis and kinase assays, we showed that HSP110 directly interacts with STAT6 and favors its phosphorylation. The combination of iHSP110-33 and selinexor induces a synergistic reduction of STAT6 phosphorylation and of lymphoma cell growth in vitro and in vivo. In biopsies from PMBL patients, we show a correlation between HSP110 and STAT6 phosphorylation levels., Conclusions: These findings suggest that HSP110 could be proposed as a novel target in PMBL and cHL therapy., (© 2024. The Author(s).)

Neuroblastoma is rare in the adult population, especially in thoracic or mediastinal locations, with only 25 previously reported cases. We report an additional example of primary thymic neuroblastoma in a previously asymptomatic 71-year-old man with an anterior mediastinal mass who underwent robotic excision with pericardium and adjacent lung. The tumor was a 5.2 cm partially encapsulated, white-tan and rubbery mass with grossly identifiable areas of necrosis (25%) and hemorrhage. Histologically, the specimen showed a rim of adipose tissue and residual thymic tissue with areas of cystic thymic epithelium and prominent lymphoid tissue containing Hassall's corpuscles. The tumor was composed of uniform, round cells with scant cytoplasm and small nuclei with inconspicuous nucleoli set within a background of conspicuous neuropil. Mitotic figures were easily found. By immunohistochemistry, the tumor cells expressed synaptophysin, chromogranin, NKX2.2 (diffuse, nuclear), GFAP (patchy), SMI31 (neurofilament) (focal, cytoplasmic), and TdT (diffuse, nuclear), while lacking expression of CD99, TTF-1, CK 20, MCPyV, PHOX2B, Olig2, OCT3/4, CD45, CD3 and PAX5. S100 protein was negative in the neuroblastic cells, with scattered positive cells in a vague sustentacular-like pattern. Fluorescence in situ hybridization for isochromosome 12p and EWSR1 gene rearrangement were negative. As thymic neuroblastoma is extremely rare in adults, a neuroblastic tumor of germ cell origin (either primary or metastatic) or spread from a sinonasal tract tumor should be excluded because of differing treatments and prognoses. The properties of these rare neoplasms appear similar to olfactory neuroblastoma rather than pediatric-type neuroblastoma., (© 2023. The Author(s).)

Vasculogenic mesenchymal tumor (VMT), a primitive mesenchymal neoplasm enriched by various-sized atypical vessels, is a new entity that develops in mediastinal germ cell tumors (GCTs) with yolk sac tumor (YST) components after chemotherapy. Notably, patients with VMT in the residual GCT have increased risk of developing sarcomas or hematopoietic malignancies. Here, we report a late-teenage male patient with residual teratoma and high-grade VMT after chemotherapy for a mediastinal mixed GCT, including YST. Whole-exome sequencing revealed biallelic inactivation of TP53 and extensive copy number alterations that suggested whole-genome doubling. The biopsy tissue of the mixed GCT before chemotherapy exhibited overlapping genetic alterations to those in the VMT. Immunohistochemical analyses of the VMT showed that the abnormal vessels were positive for cytokeratin, glypican 3, EZH2, and IMP3. The findings that VMT inherits the genetic alterations of pre-existing mixed GCT and exhibits a partly YST-like immunophenotype might contribute to its clinical aggressiveness., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Classic Hodgkin lymphoma (CHL) patients may infrequently present with a prior or recurrent disease with discordant histology resembling non-Hodgkin lymphomas. These include primary mediastinal large B-cell lymphoma (PMBL), diffuse large B-cell lymphoma (DLBCL), or mediastinal gray-zone lymphoma (MGZL). Such patients are often refractory to standard therapy and their diagnosis is hampered by significant morphologic and immunophenotypic overlap and insufficient molecular data. Among 509 CHL patients seen at an academic medical center, 6 patients had a prior or subsequent diagnosis different from CHL. Paired tissue samples were evaluated by targeted mutational analysis using a 164-gene panel. Our findings show multiple shared variants indicative of a clonal relationship between the CHL and the PMBL, DLBCL, or MGZL diagnoses. Most frequent mutated genes included TNFAIP3 (4 of 6, 66.7%), STAT6 (3 or 6, 50%), ARID1A (3 of 6, 50%), and XPO1 (3 of 5, 60%). Three patients showed the same oncogenic variant within the XPO1 gene (E571K), and mutations in TNFAIP3 and B2M were observed in 2 of the 5 patients with shared variants. In addition, differences in the mutation profile between the lymphoma pairs were also observed, which could represent clonal evolution. Mutational profiling could be of benefit in patients with recurrent/refractory disease with discordant histology, where the clonal relationship could be helpful to inform and guide therapeutic decisions. These findings provide further evidence of a true biological continuum surrounding CHL, PMBL, DLBCL, and MGZL and shed light on underlying genetic events and their clinical impact., Competing Interests: Conflicts of Interest and Source of Funding: Institutional seed funds supported this study. The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Mediastinal yolk sac tumors (YSTs) are highly aggressive germ cell tumors with an extremely poor prognosis. Radiotherapy plays an important role in the treatment of mediastinal YSTs. To maximize benefit from radiotherapy in patients with mediastinal YSTs, exploring functionally relevant biomarkers is essential. Previous studies have demonstrated that mutations in DNA-damage repair (DDR) genes, including BRCA1/2 , potentially enhance sensitivity to radiotherapy in solid tumors. However, DDR-gene mutations, as possible predictive biomarkers for radiotherapy in primary mediastinal YSTs, have not yet been reported. Herein, we report a 29-year-old male patient with a refractory metastatic primary YST involving a germline frameshift mutation in the BRCA2 gene (NM&#95;000059.3: exon11: c.4563&#95;4564delAT: L1522fs). During treatment alternation, the patient was found to respond poorly to chemotherapy with or without an immune checkpoint inhibitor but well to radiotherapy. Finally, the patient achieved approximately 17 months of overall survival. To the best of our knowledge, this case report is the first to describe a remarkable response to local radiotherapy in a patient with a refractory metastatic mediastinal YST involving a DDR-gene mutation (germline BRCA2 frameshift variation). This case report provides insightful clues for precision radiotherapy in clinical practice.

Background: Primary mediastinal nonseminoma germ cell tumors (PMNSGCT) are a subgroup of nonseminoma germ cell tumors (GCT) with poor prognosis. In this study, PMNSGCT-specific genomic landscape was analyzed and correlated with clinical outcomes., Methods: DNA was extracted and sequenced from 28 archival tumor tissue of patients with mediastinal GCT (3 seminoma and 25 nonseminoma). Overall survival (OS) and association with gene alterations were estimated using the Kaplan-Meier and univariate Cox regression methods., Results: Three patients (11%) had a karyotype XXY, 17/28 (61%) tumor samples presented chromosome 12p amplification. Somatic mutations were detected in 19/28 (68%) samples. The most frequently mutated genes were: TP53 (13/28; 46%), KIT (5/28; 18%), and KRAS (5/28; 18%). Deleterious TP53 alterations were associated with significantly reduced overall survival (HR: 7.16; P = .012)., Conclusions: TP53 alterations are common in PMNSGCT and are associated with reduced overall survival, potentially underlying the poor sensitivity to chemotherapy observed in these patients., (© The Author(s) 2022. Published by Oxford University Press.)

Neoplastic cartilage is a common component of teratomas in type II germ cell tumors. Although IDH1/2 mutations have been well-described in somatic cartilaginous tumors, ranging from benign enchondromas to highly aggressive dedifferentiated chondrosarcomas, the presence of IDH1/2 mutations in cartilaginous neoplasms arising from germ cell tumors has not been previously investigated. To better understand the relationship between these tumors and their bone/soft tissue counterpart, we studied the IDH1/2 mutational status of 20 cases of primary mediastinal mixed germ cell tumors with areas of readily identifiable cartilaginous differentiation. Our study found that cartilaginous lesions arising in germ cell tumors have a different frequency and distribution of IDH1/2 mutations compared to those at somatic sites. We identified IDH1/2 mutations in only 15% (3/20) of cases, compared to a frequency in the literature among differentiated chondroid tumors of bone and soft tissue of 54%, a highly significant decreased frequency (p = 0.0011; chi-square test). Furthermore, they were exclusively IDH2 R172 mutations that occurred at a non-significant, increased frequency in the germ cell tumor group compared to conventional chondrosarcoma (15% vs. 5%, respectively, p > 0.05, chi-square test). The unexpected finding, therefore, was entirely attributable to the absence of IDH1 R132 mutation in chondroid neoplasia of germ cell origin (p < 0.00001, Fisher exact test). Our results suggest that a subset of cartilaginous lesions arising within type II germ cell tumors have a similar oncogenic mechanism to their bone/soft tissue counterpart but that the majority form using different oncogenic mechanisms compared to their somatic counterparts., (© 2022. The Author(s), under exclusive licence to United States & Canadian Academy of Pathology.)

Development of primary mediastinal B-cell lymphoma (PMBL) is driven by cumulative genomic aberrations. We discovered a unique copy-neutral loss of heterozygosity (CN-LOH) landscape of PMBL which distinguishes this tumor from other B-cell malignancies, including the biologically related diffuse large B-cell lymphoma. Using single nucleotide polymorphism array analysis we identified large-scale CN-LOH lesions in 91% (30/33) of diagnostic PMBLs and both investigated PMBL-derived cell lines. Altogether, the cohort showed 157 extra-large (25.3-248.4 Mb) CN-LOH lesions affecting up to 14 chromosomes per case (mean of 4.4) and resulting in a reduction of heterozygosity an average of 9.9% (range 1.3-51%) of the genome. Predominant involvement of terminal chromosomal segments suggests the implication of B-cell specific crossover events in the pathogenesis of PMBL. Notably, CN-LOH stretches non-randomly clustered on 6p (60%), 15 (37.2%), and 17q (40%), and frequently co-occurred with homozygous mutations in the MHC I (6p21), B2M (15q15), and GNA13 (17q23) genes, respectively, as shown by preliminary whole-exome/genome sequencing data. Altogether, our findings implicate CN-LOH as a novel and distinct mutational process contributing to the molecular pathogenesis of PMBL. The aberration acting as "second hit" in the Knudson hypothesis, ranks as the major mechanism converting to homozygosity the PMBL-related driver genes. Screening of the cohort of 199 B cell leukemia/lymphoma whole-genomes revealed significant differences in the CN-LOH landscape of PMBL and other B-cell malignancies, including the biologically related diffuse large B-cell lymphoma., (© 2022 Wiley Periodicals LLC.)

Primary mediastinal large B-cell lymphoma (PMBCL) is a separate entity in the World Health Organization's classification, based on clinicopathologic features and a distinct molecular signature that overlaps with nodular sclerosis classic Hodgkin lymphoma (cHL). Molecular classifiers can distinguish PMBCL from diffuse large B-cell lymphoma (DLBCL) using ribonucleic acid derived from paraffin-embedded tissue and are integral to future studies. However, given that ∼5% of DLBCL can have a molecular PMBCL phenotype in the absence of mediastinal involvement, clinical information remains critical for diagnosis. Studies during the past 10 to 20 years have elucidated the biologic hallmarks of PMBCL that are reminiscent of cHL, including the importance of the JAK-STAT and NF-κB signaling pathways, as well as an immune evasion phenotype through multiple converging genetic aberrations. The outcome of PMBCL has improved in the modern rituximab era; however, whether there is a single standard treatment for all patients and when to integrate radiotherapy remains controversial. Regardless of the frontline therapy, refractory disease can occur in up to 10% of patients and correlates with poor outcome. With emerging data supporting the high efficacy of PD1 inhibitors in PMBCL, studies are underway that integrate them into the up-front setting., (© 2022 by The American Society of Hematology.)

The development of clonally related hematologic neoplasms in the setting of primary mediastinal germ cell tumors (PMGCTs) has been recognized previously and is associated with a dismal prognosis. However, the presentation of hematologic neoplasms as chronic myelomonocytic leukemia (CMML) and hemophagocytic lymphohistiocytosis (HLH) has been rarely reported. Here we report two patients with PMGCTs and hematologic neoplasms. The PMGCT was composed mostly of yolk sac tumor whereas the hematologic neoplasms had morphologic features that resembled CMML and HLH. The hematologic neoplasms from both patients harbored isochromosome 12p [i(12p)] and TP53 mutations, supporting a clonal relationship between these tumors. This association represents a unique clinical syndrome that likely contributes to the poor clinical outcome of these patients., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Cardiac undifferentiated pleomorphic sarcoma (UPS) is a rare malignancy. Several studies have revealed frequent MDM2, CDK4, PDFGRA, and KIT amplifications and CDKN2A and CDKN2B deletions. Cases lacking the above copy number alterations may harbor alternative driver mutations; however, little is known about such occurrences. This study was conducted to gain further insights into the molecular features of cardiac UPS using targeted sequencing of 560 cancer-related genes, and fluorescence in situ hybridization and immunohistochemistry of MDM2, CDK4, CDKN2A, TP53, and RB1 in 9 cardiac UPS cases. TP53 mutation or CDKN2A deletion was found in cases lacking MDM2 amplification. Further, p53 overexpression was detected in the case with TP53 mutation, while p16 expression was completely lost in the case with CDKN2A homozygous deletion. p16 overexpression was found in cases with MDM2 and CDK4 amplification but without CDKN2A deletion. Immunohistochemistry of MDM2, CDK4, p53, and p16 is expected to be preliminarily used for gene status analysis. As cardiac UPS and intimal sarcomas are merging into a single spectrum, mutation data for 3 cardiac UPS and 9 intimal sarcomas from the literature, as well as data for 5 cardiac UPS in our study were evaluated, and known recurrently mutated cancer driver genes, including PDGFRB, TP53, ALK, PTCH1, RET, ERBB4, JAK3, GATA1, PIK3CG, and RARA, were identified. Several new potentially actionable mutations, including those in RARA, ALK, PTCH1, RET, ROS1, ABL1, and MET, were also found. These findings improve the molecular understanding of this rare malignancy and are expected to provide a basis for developing precision therapeutics for cardiac UPS and intimal sarcomas., (Copyright © 2022. Published by Elsevier Inc.)

Few data exist concerning circulating tumor DNA (ctDNA) relevance in primary mediastinal B-cell lymphoma (PMBL). To explore this topic, we applied a 9-gene next-generation sequencing pipeline to samples from forty-four PMBL patients (median age 36.5 years). The primary endpoint was a similarity between paired biopsy/plasma mutational profiles. We detected at least one variant in 32 plasma samples (80%). The similarity between the biopsy and ctDNA genetic profiles for the 30 patients with paired mutated biopsy/plasma samples was greater than or equal to 80% in 19 patients (63.3%). We then compared PMBL ctDNA features with those of a cohort of Hodgkin lymphoma patients ( n  = 60). The top three mutated genes were SOCS1, TNFAIP3, and B2M in both lymphoma types. PMBL displayed more alterations in TNFAIP3 (71.9% vs. 46.3%, p  = 0.029) and GNA13 (46.9% vs. 17.1%, p  = 0.013) than cHL. Our 9-gene set may delineate tumor genotypes using ctDNA samples from both lymphoma types.

Myxoid pleomorphic liposarcoma is a recently defined subtype of liposarcoma, which preferentially involves the mediastinum of young patients and shows mixed histological features of conventional myxoid liposarcoma and pleomorphic liposarcoma. While myxoid pleomorphic liposarcoma is known to lack the EWSR1/FUS-DDIT3 fusions characteristic of the former, additional genetic data are limited. To further understand this tumor type, we extensively examined a series of myxoid pleomorphic liposarcomas by fluorescence in situ hybridization (FISH), shallow whole genome sequencing (sWGS) and genome-wide DNA methylation profiling. The 12 tumors occurred in 6 females and 6 males, ranging from 17 to 58 years of age (mean 33 years, median 35 years), and were located in the mediastinum (n = 5), back, neck, cheek and leg, including thigh. Histologically, all cases consisted of relatively, bland, abundantly myxoid areas with a prominent capillary vasculature, admixed with much more cellular and less myxoid foci containing markedly pleomorphic spindled cells, numerous pleomorphic lipoblasts and elevated mitotic activity. Using sWGS, myxoid pleomorphic liposarcomas were found to have complex chromosomal alterations, including recurrent large chromosomal gains involving chromosomes 1, 6-8, 18-21 and losses involving chromosomes 13, 16 and 17. Losses in chromosome 13, in particular loss in 13q14 (including RB1, RCTB2, DLEU1, and ITM2B genes), were observed in 4 out of 8 cases analyzed. Additional FISH analyses confirmed the presence of a monoallelic RB1 deletion in 8/12 cases. Moreover, nuclear Rb expression was deficient in all studied cases. None showed DDIT3 gene rearrangement or MDM2 gene amplification. Using genome-wide DNA methylation profiling, myxoid pleomorphic liposarcomas and conventional pleomorphic liposarcomas formed a common methylation cluster, which segregated from conventional myxoid liposarcomas. While the morphologic, genetic and epigenetic characteristics of myxoid pleomorphic liposarcoma suggest a link with conventional pleomorphic liposarcoma, its distinctive clinical features support continued separate classification for the time being., (© 2021. The Author(s), under exclusive licence to United States & Canadian Academy of Pathology.)

Germ cell tumors (GCTs) are considered to be highly curable; however, there are major differences in the outcomes related to histology and anatomical localization. GCTs originating from the testis are, overall, sensitive to platinum-based chemotherapy, whereas GCTs originating from the mediastinum show a worse response, which remains largely unexplained. Here, we address the differences among GCTs from two different anatomical locations (testicular versus mediastinal/extragonadal), with a specific focus on the role of the P53 pathway. It was recently shown that GCTs with TP53 mutations most often localize to the mediastinum. To elucidate the underlying mechanism, TP53 knock-out lines were generated in cisplatin-sensitive and -resistant clones of the representative 2102Ep cell line (wild-type TP53 testicular GCT) and NCCIT cell line (hemizygously mutated TP53 , mutant TP53 mediastinal GCT). The full knock-out of TP53 in 2102Ep and resistant NCCIT resulted in an increase in cisplatin resistance, suggesting a contributing role for P53, even in NCCIT, in which P53 had been reported to be non-functional. In conclusion, these results suggest that TP53 mutations contribute to the cisplatin-resistant phenotype of mediastinal GCTs and, therefore, are a potential candidate for targeted treatment. This knowledge provides a novel model system to elucidate the underlying mechanism of clinical behavior and possible alternative treatment of the TP53 mutant and mediastinal GCTs.

Objective: To investigate the clinicopathological features and prognostic factors of primary mediastinal large B-cell lymphoma (PMBL). Methods: The clinical data of 60 patients with PMBL including 44 biopsy cases and 16 consultation cases from September 2000 to November 2019 in the Department of Pathology, China-Japan Friendship Hospital (14 cases) and Peking Union Medical College Hospital (46 cases) were enrolled. Pathologic features, immunophenotype, immunoglobulin (Ig) gene rearrangement and microRNA expression profile were retrospectively studied. Results: Of the 60 patients, 23 were males and 37 were females, age ranged from 15 to 64 years (median 28 years). Immunohistochemical staining showed that the tumor cells were positive for pan-B cell antigens, CD30 (77.4%, 24/31), CD23 (73.1%, 19/26), MUM1 (45.8%, 11/24), Ki-67 index ≥70 % (90.6%, 29/32). EBER in situ hybridization was analyzed in 21 PMBL, only one case (4.8%) was positive. Ig gene rearrangement was performed in 20 cases, and seven were positive (35.0%). MicroRNA gene expression profiles were analyzed in seven cases of PMBL and nine cases of diffuse large B-cell lymphoma, and there were 33 microRNAs with significant difference ( P <0.05). Univariate analysis indicated that the poor prognostic factors included serum lactate dehydrogenase (LDH) level,International Prognostic Index (IPI) score ≥3, stages Ⅲ-Ⅳ, chemotherapy not combined with rituximab and MUM1 positivity ( P <0.05). Multivariate analysis showed that the treatment combined with rituximab was independently related to prognosis ( P <0.05). Conclusions: PMBL is different from diffuse large B-cell lymphoma in clinicopathologic features, immunophenotypic presentation and molecular features. The prognostic factors, molecular genetics and immunological characteristics reveal that this study has enriched our understanding of the biology of PMBL, thus providing evidence and strategies for treatment.

Primary mediastinal large B-cell lymphoma (PMBL) is a type of aggressive B-cell lymphoma that typically affects young adults, characterized by presence of a bulky anterior mediastinal mass. Lymphomas with gene expression features of PMBL have been described in nonmediastinal sites, raising questions about how these tumors should be classified. Here, we investigated whether these nonmediastinal lymphomas are indeed PMBLs or instead represent a distinct group within diffuse large B-cell lymphoma (DLBCL). From a cohort of 325 de novo DLBCL cases, we identified tumors from patients without evidence of anterior mediastinal involvement that expressed a PMBL expression signature (nm-PMBLsig+; n = 16; 5%). A majority of these tumors expressed MAL and CD23, proteins typically observed in bona fide PMBL (bf-PMBL). Evaluation of clinical features of nm-PMBLsig+ cases revealed close associations with DLBCL, and a majority displayed a germinal center B cell-like cell of origin (GCB). In contrast to patients with bf-PMBL, patients with nm-PMBLsig+ presented at an older age and did not show pleural disease, and bone/bone marrow involvement was observed in 3 cases. However, although clinically distinct from bf-PMBL, nm-PMBLsig+ tumors resembled bf-PMBL at the molecular level, with upregulation of immune response, JAK-STAT, and NF-κB signatures. Mutational analysis revealed frequent somatic gene mutations in SOCS1, IL4R, ITPKB, and STAT6, as well as CD83 and BIRC3, with the latter genes significantly more frequently affected than in GCB DLBCL or bf-PMBL. Our data establish nm-PMBLsig+ lymphomas as a group within DLBCL with distinct phenotypic and genetic features. These findings may have implications for gene expression- and mutation-based subtyping of aggressive B-cell lymphomas and related targeted therapies., (© 2021 by The American Society of Hematology.)

Background: Neuroblastoma (NB) is the most common extracranial solid tumor in children. It is known for high heterogeneity and concealed onset. In recent years, the mechanism of its occurrence and development has been gradually revealed. The purpose of this study is to summarize the clinical characteristics of children with NB and abnormal chromosome 10, and to investigate the relationship between the number and structure of chromosome 10 abnormalities and NB prognosis., Methods: Chromosome G-banding was used at the time of diagnosis to evaluate the genetics of chromosomes in patients with NB and track their clinical characteristics and prognosis. All participants were diagnosed with NB in the Medical Oncology Department of the Beijing Children's Hospital from May 2015 to December 2018 and were followed up with for at least 1 year., Results: Of all 150 patients with bone marrow metastases, 42 were clearly diagnosed with chromosomal abnormalities. Thirteen patients showed abnormalities in chromosome 10, and chromosome 10 was the most commonly missing chromosome. These 13 patients had higher LDH and lower OS and EFS than children with chromosomal abnormalities who did not have an abnormality in chromosome 10. Eight patients had both MYCN amplification and 1p36 deletion. Two patients had optic nerve damage and no vision, and one patient had left supraorbital metastases 5 months after treatment., Conclusions: The results indicated that chromosome 10 might be a new prognostic marker for NB. MYCN amplification and 1p36 deletion may be related to chromosome 10 abnormalities in NB. Additionally, NB patients with abnormal chromosome 10 were prone to orbital metastases.

The mutational landscape of gray zone lymphoma (GZL) has not yet been established, and differences from related entities are largely unknown. Here, we studied coding sequence mutations of 50 Epstein-Barr virus (EBV)-negative GZLs and 20 polymorphic EBV+ diffuse large B-cell lymphoma (DLBCL) not otherwise specified (poly-EBV-L) in comparison with classical Hodgkin lymphoma (cHL), primary mediastinal large B-cell lymphoma (PMBCL), and DLBCL. Exomes of 21 GZL and 7 poly-EBV-L cases, along with paired constitutional DNA, were analyzed as a discovery cohort, followed by targeted sequencing of 217 genes in an extension cohort of 29 GZL and 13 poly-EBV-L cases. GZL cases with thymic niche involvement (anterior mediastinal mass) exhibited a mutation profile closely resembling cHL and PMBCL, with SOCS1 (45%), B2M (45%), TNFAIP3 (35%), GNA13 (35%), LRRN3 (32%), and NFKBIA (29%) being the most recurrently mutated genes. In contrast, GZL cases without thymic niche involvement (n = 18) had a significantly distinct pattern that was enriched in mutations related to apoptosis defects (TP53 [39%], BCL2 [28%], BIRC6 [22%]) and depleted in GNA13, XPO1, or NF-κB signaling pathway mutations (TNFAIP3, NFKBIE, IKBKB, NFKBIA). They also exhibited more BCL2/BCL6 rearrangements compared with thymic GZL. Poly-EBV-L cases presented a distinct mutational profile, including STAT3 mutations and a significantly lower coding mutation load in comparison with EBV- GZL. Our study highlights characteristic mutational patterns in GZL associated with presentation in the thymic niche, suggesting a common cell of origin and disease evolution overlapping with related anterior mediastinal lymphomas., (© 2021 by The American Society of Hematology.)

We report 55 postchemotherapy resections of primary nonseminomatous mediastinal germ cell tumors with prominent vasculogenic features showing the formation of rudimentary to well-developed neoplastic vessels within primitive mesenchyme. These cases represented 25% of a cohort of 221 such specimens. The patients were 19 to 49 years old (mean, 28 y) and 98% had serological evidence of yolk sac tumor. The vasculogenic lesions, felt to represent a neoplastic reiteration of embryonic vasculogenesis in the splanchnic mesoderm of the yolk sac, were further subdivided into teratoma with vasculogenic stroma (n=9), vasculogenic mesenchymal tumor (VMT) (n=42, further classified into low grade [n=24] and high grade [n=18]), and angiosarcoma (n=4). The distinction of teratoma with vasculogenic stroma from VMT was based solely on the greater extent of VMT (exceeding 1 low power [×4 objective] microscopic field), with both categories showing a spectrum of vessels lined by atypical endothelium in a nonendothelial neoplastic stroma that often also generated vascular walls comprised of atypical smooth muscle. The angiosarcomas showed stratification of highly atypical endothelial cells or anastomosing vessels lined by nonstratified but cytologically similar endothelium. Immunohistochemical studies supported the generation of neoplastic vessels from the tumor stroma, most commonly by the development of stromal clefts showing reactivity for podoplanin, CD34, and occasionally ERG, followed by the gradual development from the clefts of thin-walled vessels that later became encircled by stromal cells showing smooth muscle differentiation by immunohistochemistry. Occasionally, round collections of stromal erythrocytes became surrounded by stromal cells to generate blood vessels. Fluorescence in situ hybridization showed chromosome 12p copy number increase in both the endothelial component and stromal component in 8/9 VMT cases and in 1/1 angiosarcoma. On follow-up, no patient with teratoma with vasculogenic stroma had evidence of a subsequent vascular tumor or sarcoma, whereas 8 of the 35 (23%) patients with VMTs (2 low grade and 6 high grade) and meaningful follow-up developed sarcoma (1 angiosarcoma, 2 rhabdomyosarcomas, and 5 not further characterized). The difference between low-grade and high-grade tumors was of borderline significance (P=0.058). Two of the 4 patients with angiosarcoma died of metastatic angiosarcoma, with the other 2 disease-free at 6.8 and 7 years. Compared with the 165 patients with follow-up and no vasculogenic lesions, there was a highly significant (P=4.3×10-5) association of any vasculogenic lesion with sarcomatoid tumors during the clinical course of VMT patients. In addition, 5/46 patients with follow-up and vasculogenic lesions (11%) died of either leukemia or myelodysplastic syndrome compared with 2 of 166 (1%) lacking them (P=0.0012). Three of the 5 patients had identifiable immature hematopoietic cells within their vasculogenic lesions, but 4 other VMT patients with these did not develop leukemia or myelodysplasia. We conclude: (1) vasculogenic lesions are frequent in postchemotherapy resections of primary mediastinal germ cell tumors with yolk sac tumor components; (2) they mostly consist of neoplastic vessels in a stroma that also generates neoplastic vascular walls of smooth muscle; (3) VMTs are associated with an increased incidence of sarcomas, even though most vasculogenic lesions in this context do not meet criteria for angiosarcoma; (4) the presence of vasculogenic lesions in postchemotherapy resections of primary mediastinal germ cell tumors place patients at increased risk for leukemia or myelodysplasia., Competing Interests: Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Extragonadal germ cell tumors (GCTs) are thought to arise as a result of local transformation of primordial gonadal cells (PGCs) that become misplaced during embryogenesis. With the exception of bilateral testis tumors, metachronous GCT (i.e., occurring at a site classically described for primary GCTs) are rare events., Patients and Methods: The clinical, radiological, and molecular data (if available) of patients with metachronous GCT were analyzed., Results: Three Caucasian males were identified: case 1 presented with a pineal germinoma 19 years after a mediastinal seminoma that had been treated with chemotherapy, case 2 presented with a pineal non-seminomatous GCT (NSGCT) that occurred three years after a mediastinal seminoma treated with chemotherapy, and case 3 presented with a mediastinal seminoma concomitant with a suprasellar germinoma that occurred two years after a stage I testicular NSGCT treated exclusively with surgery. None of these patients had a positive family history or disorder of sex development. Molecular data were available for cases 2 and 3. In case 2, a CHEK2 gene biallelic inactivation in the second tumor suggested chemoresistance to cisplatin. This was further confirmed by tumor progression during second-line treatment. In case 3, the molecular analysis revealed different profiles in the three tumors, thus suggesting distinct tumor cell origins., Conclusion: These rare cases should alert clinicians of the possibility of multiple GCTs that should not be considered to be relapses. The underlying physiopathology is unknown, but multiple PGC mismigrations is a likely cause. Initial treatment with cisplatin may select chemo-resistant clones, thereby making the subsequent treatment more of a challenge.

Young males have a unique but rare predilection to develop mediastinal nonseminomatous germ cell tumors (NSGCTs) and concomitant acute megakaryoblastic leukemia (AMKL). Common cytogenetic and molecular abnormalities such as isochromosome 12p and somatic Tumor Protein P53(TP53) and Phosphatase And Tensin Homolog (PTEN) mutations have been reported in the presumed mutual neoplastic clones of origin. We report the case of a 17-year-old male who presented with a mediastinal NSGCT with high-grade sarcomatous transformation and a diagnosis of AMKL approximately 4 months later. Next-generation sequencing revealed identical KRAS Proto-Oncogene, GTPase (KRAS) p.Ala146Thr, TP53 p.Leu257Pro, and PTEN p.Leu181Pro missense mutations at similar variant allele frequencies in both the NSGCT and AMKL samples. Cytogenetic and microarray analyses detected shared copy gains in all chromosomes except chromosomes 9, 13, and Y. Multiple additional clonal chromosomal alterations were detected in the AMKL sample when compared with the NSGCT. This case emphasizes the shared clonal origins of these malignancies and identifies KRAS and other copy number alterations as potential molecular drivers in a subset of these combined diseases.

Mediastinal gray zone lymphoma (MGZL) has immunopathologic features between classical Hodgkin lymphoma (cHL) and primary mediastinal thymic B-cell lymphoma (PMBL), leading to uncertainty regarding its biological relationship to these entities. We performed gene expression profiling from patients with MGZL (20), cHL (18), and PMBL (17) and show MGZL clusters between cHL and PMBL. Expression signatures reveal germinal B-cell and IFN regulatory factor 4 (IRF4) signatures were relatively low in MGZL and cHL compared with PMBL, indicating downregulation of the B-cell program in MGZL, a hallmark of cHL. T-cell and macrophage signatures were higher in MGZL and cHL compared with PMBL, consistent with infiltrating immune cells, which are found in cHL. The NFκB signature was higher in MGZL than PMBL, and like cHL, MGZL and PMBL express NFκB inducing kinase (NIK), indicating noncanonical signaling. These findings indicate that while MGZL has distinctive clustering, it is biologically closer to cHL., Competing Interests: Disclosure of Potential Conflicts of Interest No potential conflicts of interest were disclosed.

Teratoma with malignant transformation is a rare type of malignant teratoma. In the present case, we describe a patient with salivary gland carcinoma (SGC) generating in mediastinal mature teratoma. Next-generation sequencing showed BRCA1 and KRAS somatic mutations, which might be associated with malignant transformation of the mediastinal mature teratomas. To our knowledge, the present case is the first report of coexistence of BRCA1 and KRAS mutations in mature cystic teratoma with malignant transformation to SGC. And the tumor showed a good response to chemotherapy with cisplatin and paclitaxel according to the transformed histology.

Synovial sarcoma (SS) is an aggressive tumor that most often affects the deep soft tissues in young adults. Intrathoracic SS is rare and is associated with poor outcome, highlighting the urgent need for a novel therapeutic strategy. In the process of clinical sequencing, we identified two patients with intrathoracic SS harboring the BRAF V600E mutation. The patients were women aged 32 and 23 years, and both presented with SS18-SSX2-positive monophasic SS in the thoracic cavity. BRAF V600E mutations were detected by next generation sequencing, and validated immunohistochemically by diffuse intense positivity to BRAF V600E mutation-specific antibodies. The phosphorylated ERK (pERK) immunohistochemistry result was also positive. One patient received a combination therapy of dabrafenib and trametinib, which led to tumor shrinkage. However, the tumor growth progressed 7.5 months later with an additional NRAS Q61K mutation. Immunohistochemical screening of 67 archival SS tumor samples failed to identify additional samples with BRAF V600E mutation. However, 32% of BRAF V600E-negative cases was positive for pERK, and one of the six tumors showing the highest pERK expression harbored an FGFR2-activating mutation. This is the first report of targetable BRAF mutation in a small subset of SS. Our study suggests involvement of the mitogen-activated protein kinase pathway and the potential clinical implication of BRAF mutation screening in SS.

Background: Recently, copy number alteration (CNA) of 9p24.1 were demonstrated in 10% of diffuse large b-cell lymphoma (DLBCL), with gene expression and mutation profiles that were similar to those of primary mediastinal large B-cell lymphoma (PMBCL). However, their CNA-based profile and clinical impact still remain unclear., Methods: Multiplex ligation-dependent probe amplification were employed to investigate the prevalence of JAK2/PD-L2 amplification in DLBCL and their CNA-based pattern of driver genes. The clinical outcome and characteristics were also analyzed., Results: Using unsupervised hierarchical clustering, a small group of DLBCL (10.5%, 8/76) was clustered together with PMBCL as Cluster&#95;2, demonstrating amplification of JAK2 (100%,8/8) and PD-L2 (75.0%,6/8). This subgroups of DLBCL demonstrated significant higher expression of PD-L1 than those with MYD88 L265P mutation(p = 0.024). And they exhibited dismal OS and PFS as compared with DLBCL&#95;others(p = 0.003 and 0.001, respectively), which is similar to DLBCL with MYD88 L265P mutation., Conclusions: DLBCL with amplification of JAK2/PD-L2 exhibits CNA pattern that is similar to PMBCL, and demonstrates unfavorable clinical outcome that resembles those with MYD88 L265P mutation. It is essential to identify this subgroup of DLBCL who may acquire more benefits from the JAK2 and PD-L1 signaling inhibition.

Primary mediastinal large B-cell lymphoma (PMLBCL) is an aggressive lymphoma characteristic with distinct clinical, morphologic, and immunophenotypic features. The rearrangements of C-MYC, BCL2 and/or BCL6 which are common in diffuse large B-cell lymphoma (DLBCL) are typically absent in PLMBCL. Here we proved a novel case of PMLBCL with concurrent rearrangements of C-MYC and BCL2. Histology showed typical pathomorphological features of PLMBCL. Fluorescent in situ hybridization (FISH) studies showed rearrangements of C-MYC and copy number variation (CNV) of BCL2 gene. It is not well known on the clinical significance of rearrangements of C-MYC and BCL2 genes in PMLBCL. The case gives evidence that cytogenetic testing is necessary for PMLBCLs to get precise clinical evaluation and appropriate treatment.

Aims: Ectomesenchymal chondromyxoid tumour (ECT) is a rare benign intraoral tumour which almost exclusively presents as a small mass of the anterior dorsal tongue. Recently, the RREB1-MRTFB (previously known as MKL2) fusion gene has been identified in 90% of ECTs, all located in the tongue, emphasising its genetic distinctiveness. Here, we report two mesenchymal tumours involving the superior mediastinum of adult women with RREB1-MRTFB fusions., Methods and Results: Both tumours presented as well-circumscribed paravertebral masses that were clinically suspected to be schwannoma. After fragmented resection, recurrence was not observed at 27 and 18 months. Although tumours were originally unclassifiable, next-generation sequencing detected identical RREB1 (exon 8)-MRTFB (exon 11) fusion transcripts, which were validated by reverse transcriptase-polymerase chain reaction, Sanger sequencing, and fluorescence in-situ hybridisation. Both tumours shared hyalinised areas with round cells embedded in a cord or reticular manner. The tumour cells showed mild nuclear atypia of possible degenerative type with very low mitotic activity, and were at least focally positive for S100, glial fibrillary acidic protein, smooth muscle actin and epithelial membrane antigen. Overall, these findings suggest that they may represent previously undescribed extra-glossal ECT involving the mediastinum. However, the histology was not classic for ECT, because that in case 2 was predominated by storiform growth of spindle cells, whereas the tumour in case 1 lacked myxoid change., Conclusions: We have provided the first evidence that RREB1-MRTFB fusion is not limited to tumours in the head region, and whether such tumours represent extra-glossal ECTs requires further research., (© 2020 John Wiley & Sons Ltd.)

Introduction: Isolated myeloid sarcoma (MS) is characterized by extramedullary immature myeloid cell infiltration without bone marrow involvement. The diagnosis of isolated MS is sometimes difficult in cases without expression of typical immunohistochemical markers, such as CD64, MPO or lysozyme. Clinical presentation: We report a case of isolated MS involving the mediastinum, with negative staining of MPO and lysozyme, which was misdiagnosed for 20 months. A comprehensive analysis in our institution showed MS with a characteristic staining pattern positive for CD34, CD117 and CD33, but negative for MPO, lysozyme, CD3 and CD79a. Next-generation sequencing (NGS) targeting 112 acute myeloid leukemia (AML)- and myelodysplastic syndromes (MDS)-associated genes confirmed the existence of an ASXL1 p.R693X mutation with a frequency of 13.17% of total cells. The patient acquired sustainable remission under the alternative treatment of intermediate-dose cytarabine and decitabine. Discussion and conclusion: The ASXL1 p.R693X mutation, a truncated mutation, has been widely reported to be associated with poor prognosis in myeloid malignance. We report the role of this mutation and recommend the utilization of NGS to discover more profound pathobiological information with limited samples, facilitate the diagnosis, and further clarify the uncertainties of prognosis and treatment in more isolated MS patients.

Diffuse large B-cell lymphoma (DLBCL) encompasses a group of aggressive B-cell non-Hodgkin lymphomas with striking genetic heterogeneity and variable clinical presentations. Among these is primary mediastinal B-cell lymphoma (PMBL), which has unique clinical and molecular features resembling Hodgkin lymphoma. Treatment of DLBCL is usually curative, but identifiable subsets at highest risk for treatment failure may benefit from intensified chemotherapy regimens and/or targeted agents added to frontline therapy. Recent comprehensive genomic analyses have identified distinct genetic subtypes of DLBCL with characteristic genetic drivers and signaling pathways that are targetable. Immune therapy with chimeric antigen receptor T cells and checkpoint inhibitors has revolutionized the treatment of relapsed or refractory disease, and antibody drug conjugates have weaponized otherwise intolerable cytotoxic agents. Ongoing clinical trials are further refining the specificity of these approaches in different genetic subtypes and moving them from the setting of recurrent disease to frontline treatment in high-risk patient populations.

Competing Interests: Die Autoren geben an, dass kein Interessenkonflikt besteht.

A growing number of studies suggest a tumor suppressor role for the SWI/SNF complex involved in the remodeling of chromatin. Alterations of this complex have been found in many tumors of different origins, with topographic, morphologic and phenotypic diversity. Notably, they define 2 types of thoracic tumors: SMARCA4-deficient non-small cell lung carcinoma and SMARCA4-deficient sarcoma. Some clinical features appear to be common to both, such as intrathoracic localization, smoking exposure, male predominance and poor prognosis. However, the histological distinction between these two entities is sometimes difficult and it is not excluded that these entities belong to the same tumor spectrum with different degrees of differentiation. The therapy of these tumors is not yet codified. These tumors do not seem associated with oncogenic driver mutations allowing the prescription of targeted therapy, but immunotherapy has been shown to be effective in rare reported cases. More specific treatments using EZH2 inhibitors also seem promising in SMARCA4 deficient sarcomas., (Copyright © 2019 Société Française du Cancer. Published by Elsevier Masson SAS. All rights reserved.)

T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/LBL) is usually diagnosed based on the presence of immature lymphoid marker terminal deoxynucleotidyl transferase (TdT), and T-cell specific markers, specifically CD3, by immunohistochemistry (IHC) staining on bone marrow and/or extramedullary tissue. We present a novel, TdT and CD3 negative, aggressive early T-cell precursor LBL (ETP-LBL) initially misdiagnosed as a high grade B-cell lymphoma due to expression of CD79a and the erroneous detection of BCL2/IGH fusion. The patient was eventually evaluated using molecular diagnostic techniques, including fluorescence in situ hybridization (FISH) and next generation sequencing (NGS) assays that demonstrated PICALM-MLLT10 fusion and a NOTCH1 mutation in the absence of BCL2/IGH fusion. The use of NGS, specifically mate-pair sequencing (MPseq), subsequently confirmed an in-frame PICALM-MLLT10 fusion. Our retrospective analysis showed that PICALM-MLLT10 fusion has no association with CD3/TdT negativity, as 6/49 T-ALL/LBL cases from Mayo Clinic database (01/1998-09/2018), including this case, were noted to have PICALM-MLLT10 fusion; however, none of the other cases were associated with CD3/TdT negativity. We emphasize the importance of a comprehensive hematopathologic evaluation including multiple molecular studies for the appropriate interrogation and classification of a difficult acute leukemia diagnosis, and to prevent potential diagnostic errors of clinical significance., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Neuroendocrine tumors (NETs) rarely occur in the mediastinum and their etiology and pathogenesis are still unclear., Objectives: This study assessed inherited or de novo mutations in familial mediastinal NETs., Method: DNA samples from 4 patients were subjected to the whole-exome sequencing, and Sanger sequencing was used to identify Deleted in malignant brain tumor 1 (DMBT1) mutations in all 45 family members., Results: All patients showed a germline DMBT1 mutation at 4971C. Sanger sequencing data showed that 4 NETs and 2 carriers in the first patient's family and 2 NETs and 4 carriers in the second patient's family, respectively, had this DMBT1 mutation. The in vitro data showed that the ectopic expression of DMBT1 reduced tumor cell viability and migration by arresting the G1/S phase of the cell cycle., Conclusions: We identified a germline missense mutation in DMBT1D1657E as a susceptibility gene for familial mediastinal NETs., (© 2019 S. Karger AG, Basel.)

Primary mediastinal large B-cell lymphomas (PMBLs) are aggressive tumors that typically present as large mediastinal masses in young women. PMBLs share clinical, transcriptional, and molecular features with classical Hodgkin lymphoma (cHL), including constitutive activation of nuclear factor κB (NF-κB), JAK/STAT signaling, and programmed cell death protein 1 (PD-1)-mediated immune evasion. The demonstrated efficacy of PD-1 blockade in relapsed/refractory PMBLs led to recent approval by the US Food and Drug Administration and underscored the importance of characterizing targetable genetic vulnerabilities in this disease. Here, we report a comprehensive analysis of recurrent genetic alterations -somatic mutations, somatic copy number alterations, and structural variants-in a cohort of 37 newly diagnosed PMBLs. We identified a median of 9 genetic drivers per PMBL, including known and newly identified components of the JAK/STAT and NF-κB signaling pathways and frequent B2M alterations that limit major histocompatibility complex class I expression, as in cHL. PMBL also exhibited frequent, newly identified driver mutations in ZNF217 and an additional epigenetic modifier, EZH2. The majority of these alterations were clonal, which supports their role as early drivers. In PMBL, we identified several previously uncharacterized molecular features that may increase sensitivity to PD-1 blockade, including high tumor mutational burden, microsatellite instability, and an apolipoprotein B mRNA editing catalytic polypeptide-like (APOBEC) mutational signature. The shared genetic features between PMBL and cHL provide a framework for analyzing the mechanism of action of PD-1 blockade in these related lymphoid malignancies., (© 2019 by The American Society of Hematology.)

Purpose: Patients with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) have a poor prognosis, and their treatment represents an urgent and unmet need. Because PMBCL is associated with genetic aberrations at 9p24 and overexpression of programmed cell death-1 (PD-1) ligands (PD-L1), it is hypothesized to be susceptible to PD-1 blockade., Methods: In the phase IB KEYNOTE-013 (ClinicalTrials.gov identifier: NCT01953692) and phase II KEYNOTE-170 (ClinicalTrials.gov identifier: NCT02576990) studies, adults with rrPMBCL received pembrolizumab for up to 2 years or until disease progression or unacceptable toxicity. The primary end points were safety and objective response rate in KEYNOTE-013 and objective response rate in KEYNOTE-170. Secondary end points included duration of response, progression-free survival, overall survival, and safety. Exploratory end points included association between biomarkers and pembrolizumab activity., Results: The objective response rate was 48% (7 complete responses; 33%) among 21 patients in KEYNOTE-013 and 45% (7 complete responses; 13%) among 53 patients in KEYNOTE-170. After a median follow-up time of 29.1 months in KEYNOTE-013 and 12.5 months in KEYNOTE-170, the median duration of response was not reached in either study. No patient with complete response experienced progression, including 2 patients with complete response for at least 1 year off therapy. Treatment-related adverse events occurred in 24% of patients in KEYNOTE-013 and 23% of patients in KEYNOTE-170. There were no treatment-related deaths. Among 42 evaluable patients, the magnitude of the 9p24 gene abnormality was associated with PD-L1 expression, which was itself significantly associated with progression-free survival., Conclusion: Pembrolizumab is associated with high response rate, durable activity, and a manageable safety profile in patients with rrPMBCL.

BAF complexes are chromatin remodelling complexes made up of 15 subunits which overview transcription regulation. A subset of their subunits are notoriously linked to cancer, with the examples of SMARCB1, SMARCA4, ARID1A/1B and PBRM1. The complexes act as tumor suppressor genes, commonly mutated in a wide array of malignancies with an overrepresentation of sarcomas and tumors of the central nervous system. The recurrent inactivation of their genes points towards their driving role in the tumorigenesis of SMARCB1 in malignant rhabdoid tumors and SMARCA4 in small cell carcinoma of the ovary, hypercalcemic type. These tumors are morphologically similar composed of solid sheets of cells displaying vesicular nuclei dotted with clear chromatin and conspicuous nucleoli. Genomically, they share simple diploid profiles with no other alterations than in the culprit gene. Other mesenchymal tumors, distinct from malignant rhabdoid tumors are associated with BAF alterations, namely epithelioid sarcomas, SMARCA4-deficient thoracic sarcomas. BAF subunits are mostly inactivated through mutations or deletions but also occur through translocations in medullary carcinoma of the kidney and synovial sarcomas. Apart from tumors displaying recurrent alterations of the complexes, some variants or tumor variants display BAF alterations, including epithelioid malignant peripheral nerve sheet tumors and poorly differentiated chordomas. Lastly, some malignancies display low frequency of BAF alterations, in keeping with their passenger role in tumorigenesis with the example of dedifferentiated carcinomas, especially in colon, lung and uterus. BAF complexes alterations correlate with morphological features recognizable by microscopy, paving the way for their routine diagnosis and potential therapeutic prospects., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Background: The upregulated expression of the JAK/STAT pathway promotes tumor growth in Hodgkin lymphoma (HL) and primary mediastinal large B-cell lymphoma (PMBCL). Based on the hypothesis that JAK2 is a therapeutic target, we performed a prospective pilot study using ruxolitinib., Methods: Relapsed or refractory patients with HL or PMBCL were eligible for this study, and JAK2 amplification was assessed by fluorescence in situ hybridization. Ruxolitinib was administered orally at a dose of 20 mg twice daily for a 28-day cycle. Treatment was continued for up to 16 cycles or until progressive disease or intolerability. The primary objective was to assess the overall disease control rate comprising complete response (CR), partial response (PR), or stable disease (SD)., Results: We analyzed 13 HL patients and six PMBCL patients. All responders (one CR, five PR, and one SD) had HL whereas all cases of PMBCL progressed after first or second cycle. The disease control rate for HL was 54% (7/13) with median response duration of 5.6 months. JAK2 amplification was present in six of nine patients tested (four HL, two PMBCL), and three of these HL patients showed PR (n = 2) or SD (n = 1). None of the three HL patients shown to not have JAK2 amplification responded to ruxolitinib. Most treatment-related adverse events were grade 1 or 2 and manageable., Conclusions: Ruxolitinib has single-agent activity against HL but does not act against PMBCL with or without JAK2 amplification., Trial Registration: The study population was patients who had relapsed or refractory HL or PMBCL, and patients were registered for our pilot study after providing written informed consent between November 2013 and November 2015 (CilinicalTrials.gov: NCT01965119).

Diffuse large B-cell lymphoma (DLBCL) is a clinically and biologically heterogeneous disease. Diagnostic tools in the clinic can now identify distinct subsets characterized by unique molecular features, which are increasingly transforming how these patients are managed. Activated B-cell-like DLBCL is characterized by NF-κB activation and chronic B-cell receptor signaling and may be targeted with lenalidomide or ibrutinib in the relapsed setting. Germinal center-like DLBCL is enriched for activating EZH2 mutations, and encouraging activity has been observed for the EZH2 inhibitor tazemetostat, which now has a fast-track US Food and Drug Administration designation. Double-hit lymphoma is a high-grade B-cell lymphoma characterized by translocations of MYC and BCL2 and/or BCL6 and carries a poor prognosis. Intensive chemoimmunotherapy strategies appear to be superior to standard R-CHOP (rituximab combined with cyclophosphamide, doxorubicin, vincristine, and prednisone) as initial therapy, and anti-CD19 chimeric antigen receptor T cells are inducing remission in patients with relapsed/refractory disease who previously had few available options. Primary mediastinal (thymic) large B-cell lymphoma is a molecularly distinct large-cell lymphoma with clinical and molecular features that overlap with those of classical Hodgkin lymphoma. R-CHOP has been associated with an unacceptably high rate of primary treatment failure in this young population, whereas dose-adjusted EPOCH-R (etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin plus rituximab) produces durable remissions without the need for radiotherapy in most patients. For relapsed/refractory disease, immune checkpoint inhibitors targeting PD-1 have shown promising activity in chemotherapy-refractory disease, as have anti-CD19 chimeric antigen receptor T cells. Additional therapeutic targets, including JAK2, continue to be evaluated. The identification of discrete biological subsets is steadily moving us away from a "one-size-fits-all" approach in DLBCL., (© 2019 American Cancer Society.)