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Langerhans cell histiocytosis (LCH) is a rare disorder characterized by tissue accumulation of CD1a+CD207+ LCH cells. In LCH, somatic mutations of the BRAFV600E gene have been detected in tissue LCH cells, bone marrow CD34+ hematopoietic stem cells, circulating CD14+ monocytes, and BDCA1+ myeloid dendritic cells (DC). Targeting BRAFV600E in clonal Langerhans cells (LC) and their precursors is a potential treatment option for patients whose tumors have the mutation. The development of mouse macrophages and LCs is regulated by the CSF1 receptor (CSF1R). In patients with diffuse-type tenosynovial giant cell tumors, CSF1R inhibition depletes tumor-associated macrophages (TAM) with therapeutic efficacy; however, CSF1R signaling in LCs and LCH has not been investigated. We found through IHC and flow cytometry that CSF1R is normally expressed on human CD1a+CD207+ LCs in the epidermis and stratified epithelia. LCs that were differentiated from CD14+ monocytes, BDCA1+ DCs, and CD34+ cord blood progenitors expressed CSF1R that was downregulated upon maturation. Immature LCs migrated toward CSF1, but not IL34. Administration of the c-FMS/CSF1R kinase inhibitors GW2580 and BLZ945 significantly reduced human LC migration. In LCH clinical samples, LCH cells (including BRAFV600E cells) and TAMs retained high expression of CSF1R. We also detected the presence of transcripts for its ligand, CSF1, but not IL34, in all tested LCH cases. CSF1R and CSF1 expression in LCH, and their role in LC migration and differentiation, suggests CSF1R signaling blockade as a candidate rational approach for treatment of LCH, including the BRAFV600E and wild-type forms of the disease.

Supplementary Tables 1-2

Supplementary Figures 1-9

Supplementary figures 1-5, supplementary tables 1-9

Follicular dendritic cell (FDC) sarcomas are rare mesenchymal tumors with variable clinical, morphologic, and phenotypic characteristics. Transcriptome analysis was performed on multiple FDC sarcomas and compared with other mesenchymal tumors, microdissected Castleman FDCs, and normal fibroblasts. Using unsupervised analysis, FDC sarcomas clustered with microdissected FDCs, distinct from other mesenchymal tumors and fibroblasts. The specific endowment of FDC-related gene expression programs in FDC sarcomas emerged by applying a gene signature of differentially expressed genes (n = 1,289) between microdissected FDCs and fibroblasts. Supervised analysis comparing FDC sarcomas with microdissected FDCs and other mesenchymal tumors identified 370 and 2,927 differentially expressed transcripts, respectively, and on the basis of pathway enrichment analysis ascribed to signal transduction, chromatin organization, and extracellular matrix organization programs. As the transcriptome of FDC sarcomas retained similarity with FDCs, the immune landscape of FDC sarcoma was investigated by applying the CIBERSORT algorithm to FDC sarcomas and non-FDC mesenchymal tumors and demonstrated that FDC sarcomas were enriched in T follicular helper (TFH) and T regulatory (TREG) cell populations, as confirmed in situ by immunohistochemistry. The enrichment in specific T-cell subsets prompted investigating the mRNA expression of the inhibitory immune receptor PD-1 and its ligands PD-L1 and PD-L2, which were found to be significantly upregulated in FDC sarcomas as compared with other mesenchymal tumors, a finding also confirmed in situ. Here, it is demonstrated for the first time the transcriptional relationship of FDC sarcomas with nonmalignant FDCs and their distinction from other mesenchymal tumors.Implications: The current study provides evidence of a peculiar immune microenvironment associated with FDC sarcomas that may have clinical utility. Mol Cancer Res; 15(5); 541–52. ©2017 AACR.

Terminal tissue differentiation and function of slan+ monocytes in cancer is largely unexplored. Our recent studies demonstrated that slan+ monocytes differentiate into a distinct subset of dendritic cells (DC) in human tonsils and that slan+ cells colonize metastatic carcinoma-draining lymph nodes. Herein, we report by retrospective analysis of multi-institutional cohorts that slan+ cells infiltrate various types of non-Hodgkin lymphomas (NHL), particularly the diffuse large B-cell lymphoma (DLBCL) group, including the most aggressive, nodal and extranodal, forms. Nodal slan+ cells displayed features of either immature DC or macrophages, in the latter case ingesting tumor cells and apoptotic bodies. We also found in patients with DLBCL that peripheral blood slan+ monocytes, but not CD14+ monocytes, increased in number and displayed highly efficient rituximab-mediated antibody-dependent cellular cytotoxicity, almost equivalent to that exerted by NK cells. Notably, slan+ monocytes cultured in conditioned medium from nodal DLBCL (DCM) acquired a macrophage-like phenotype, retained CD16 expression, and became very efficient in rituximab-mediated antibody-dependent cellular phagocytosis (ADCP). Macrophages derived from DCM-treated CD14+ monocytes performed very efficient rituximab-mediated ADCP, however, using different FcγRs from those used by slan+ macrophages. Our observations shed new light on the complexity of the immune microenvironment of DLBCL and demonstrate plasticity of slan+ monocytes homing to cancer tissues. Altogether, data identify slan+ monocytes and macrophages as prominent effectors of antibody-mediated tumor cell targeting in patients with DLBCL.Significance: slan+ monocytes differentiate into macrophages that function as prominent effectors of antibody-mediated tumor cell targeting in lymphoma.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/13/3544/F1.large.jpg. Cancer Res; 78(13); 3544–59. ©2018 AACR.

The file contains 8 supplementary Figures displaying results in support of the data described in the results section.

10 Tables displaying the clinical features of patient cohorts analyzed in this study, as well as correlation analyses among the clinical features and slan+ cell content.

Summary Follicular dendritic cells (FDC) are mesenchymal-derived dendritic cells located in B-follicles where they play a pivotal role in triggering and maintaining B-cell adaptive immune response. In 1986 Dr. Juan Rosai first reported a series of neoplasms showing features of FDC and defined it as Follicular Dendritic Cell Tumor, subsequently renamed as “sarcoma” (FDCS). In its seminal and subsequent articles Rosai and colleagues highlighted the heterogeneous microscopic appearance of FDCS and its immunohistochemical and ultrastructural features. FDCS mostly occurs in extranodal sites (79.4% of cases) and lymph nodes (15.1%); in about 7%-10% of cases it is associated with hyaline-vascular Castleman disease. Given its significant growth pattern and cytological variability, FDCS can be confused with various neoplasms and even inflammatory processes. The diagnosis requires the use of a broad spectrum of FDC markers (e.g. CD21, CD23, CD35, clusterin, CXCL13, podoplanin), particularly considering that tumor antigen-loss is frequent. The inflammatory-pseudotumor-like (IPT-like) variant of FDCS, in addition to its peculiar histopathological and clinical features, is characterized by positivity of tumor cells for Epstein-Barr virus, representing a diagnostic requisite. No distinctive genetic and molecular anomalies have been identified in FDCS. It often carries an aberrant clonal karyotype and chromosomal structural alterations, frequently involving onco-suppressor genes. Direct or next generation sequencing showed alterations on genes belonging to the NF-κB regulatory pathway and cell-cycle regulators. In contrast to hematopoietic-derived histiocytic and dendritic cells tumors, FDCS typically lacks mutations in genes related to the MAPK pathway. FDCS recurs locally in 28% and metastasizes in 27% of cases. Extent of the disease, surgical resectability and histopathological features are significantly associated with the outcome. IPT-like FDCS behaves as an indolent tumor, even if it often recurs locally over years. Complete surgical excision is the gold standard of treatment. Data on targeted therapies (e.g.: tyrosine kinase inhibitors) or immune checkpoint inhibitors are very limited and responses are variable. A better understanding of the molecular drivers of this tumor may lead to potential new therapeutic strategies.

Graham Little-Piccardi-Lassueur syndrome (GLPLS) is a rare variant of lichen planopilaris, characterized by a triad of clinical signs including follicular spinous papules on the body area, scarring alopecia of the scalp and non-scarring alopecia of the groin and/or axilla. To date, fewer than 50 cases have been described in the literature. We first report a case of GLPLS investigated with non-invasive techniques such as dermoscopy and in vivo reflectance confocal microscopy (RCM) and successfully treated with narrowband-UVB (NB-UVB) phototherapy.

Tumours derived from histiocytes/macrophages and from dendritic cells are extremely rare. They mainly occur in lymphoid tissues, where they account for less than 1% of tumours, but they can be also found in extranodal sites. These neoplasms represent a heterogeneous group of diseases with a variable clinical behavior even within the same tumour entity, ranging from localized and indolent forms to systemic aggressive processes. Diagnosis is based on histological and immunophenotypic features, but overlaps occur across diseases with different biological nature and clinical course, thus correlation with clinical and radiological features is sometimes necessary for final diagnosis. The driver mutations identified during the last few years contributed to a better understanding of the pathogenesis of some of these tumours and in some of them turned out to be useful for diagnosis and treatment.

Supplemental Digital Content is available in the text., Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive neoplasm derived from plasmacytoid dendritic cells (pDCs). In this study, we investigated by immunohistochemical analysis the expression of E-cadherin (EC) on pDCs in reactive lymph nodes and tonsils, bone marrow, and in BPDCN. We compared the expression of EC in BPDCN to that in leukemia cutis (LC) and cutaneous lupus erythematosus (CLE), the latter typically featuring pDC activation. In BPDCN, we also assessed the immunomodulatory activity of malignant pDCs through the expression of several type I interferon (IFN-I) signaling effectors and downstream targets, PD-L1/CD274, and determined the extent of tumor infiltration by CD8-expressing T cells. In reactive lymph nodes and tonsils, pDCs expressed EC, whereas no reactivity was observed in bone marrow pDCs. BPDCN showed EC expression in the malignant pDCs in the vast majority of cutaneous (31/33 cases, 94%), nodal, and spleen localizations (3/3 cases, 100%), whereas it was more variable in the bone marrow (5/13, 38,5%), where tumor cells expressed EC similarly to the skin counterpart in 4 cases and differently in other 4. Notably, EC was undetectable in LC (n=30) and in juxta-epidermal pDCs in CLE (n=31). Contrary to CLE showing robust expression of IFN-I-induced proteins MX1 and ISG5 in 20/23 cases (87%), and STAT1 phosphorylation, BPDCN biopsies showed inconsistent levels of these proteins in most cases (85%). Expression of IFN-I-induced genes, IFI27, IFIT1, ISG15, RSAD2, and SIGLEC1, was also significantly (P

*** " é disponibile la seconda edizione del manuale aggiornata con le novità Horizon Europe: https://doi.org/10.5281/zenodo.6402624"*** Il seguente documento nasce nell’ambito delle attività svolte dal Gruppo di Lavoro (GdL) APRE dedicato all’Open Science e si sviluppa come un manuale d’uso per i ricercatori sul tema Scienza Aperta e, nello specifico, sull’Open Access e l’Open Data. La sua redazione ha coinvolto attivamente tutti i membri del Gruppo di lavoro, composto da rappresentanti delle biblioteche e degli uffici di supporto alla ricerca di diverse università e centri di ricerca italiani (è possibile consultare la lista dei partecipanti nell’ultima pagina di questo documento). Il manuale è il prodotto finale di un lavoro che si è svolto in 3 fasi. Inizialmente, c’è stata una fase di raccolta delle domande più comuni poste dai ricercatori presso le strutture di supporto (siano esse Biblioteche o Grant Office) dei loro enti di appartenenza in materia di Open Access e Open Data. Nella fase successiva le domande sono state consolidate e aggregate in 6 clusters: (I) I falsi miti; (II) Considerazioni individuali; (III) Peer Review e Impact Factor, (IV) La proprietà intellettuale e il contratto con l’editore; (V) Quello che i ricercatori non sanno; (VI) Open Access e Progetti Europei. Durante la terza e ultima fase dello sviluppo del documento, alcuni membri, su base volontaria, hanno curato la redazione delle risposte, successivamente emendate in più riprese dall’intero gruppo di lavoro., " é disponibile la seconda edizione del manuale aggiornata con le novità Horizon Europe: https://doi.org/10.5281/zenodo.6402624"

The endothelin-1 (ET-1) receptors were recently found to mediate pro-survival functions in multiple myeloma (MM) cells in response to autocrine ET-1. This study investigated the effectiveness of macitentan, a dual ET-1 receptor antagonist, in MM treatment, and the mechanisms underlying its activities. Macitentan affected significantly MM cell (RPMI-8226, U266, KMS-12-PE) survival and pro-angiogenic cytokine release by down-modulating ET-1-activated MAPK/ERK and HIF-1α pathways, respectively. HIF-1α silencing abrogated the ET-1 mediated induction of genes encoding for pro-angiogenic cytokines such as VEGF-A, IL-8, Adrenomedullin, and ET-1 itself. Upon exposure to macitentan, MM cells cultured in the presence of the hypoxia-mimetic agent CoCl2, exogenous ET-1, or CoCl2plus ET-1, down-regulated HIF-1α and the transcription and release of downstream pro-angiogenic cytokines. Consistently, macitentan limited significantly the basal pro-angiogenic activity of RPMI-8226 cells in chorioallantoic membrane assay. In xenograft mouse models, established by injecting NOG mice eitherviaintra-caudal vein with U266 or subcutaneously with RPMI-8226 cells, macitentan reduced effectively the number of MM cells infiltrating bone marrow, and the size and microvascular density of subcutaneous MM tumors. ET-1 receptors targeting by macitentan represents an effective anti-proliferative and anti-angiogenic therapeutic approach in preclinical settings of MM.

Follicular dendritic cell (FDC) sarcomas are rare mesenchymal tumors with variable clinical, morphologic, and phenotypic characteristics. Transcriptome analysis was performed on multiple FDC sarcomas and compared with other mesenchymal tumors, microdissected Castleman FDCs, and normal fibroblasts. Using unsupervised analysis, FDC sarcomas clustered with microdissected FDCs, distinct from other mesenchymal tumors and fibroblasts. The specific endowment of FDC-related gene expression programs in FDC sarcomas emerged by applying a gene signature of differentially expressed genes (n = 1,289) between microdissected FDCs and fibroblasts. Supervised analysis comparing FDC sarcomas with microdissected FDCs and other mesenchymal tumors identified 370 and 2,927 differentially expressed transcripts, respectively, and on the basis of pathway enrichment analysis ascribed to signal transduction, chromatin organization, and extracellular matrix organization programs. As the transcriptome of FDC sarcomas retained similarity with FDCs, the immune landscape of FDC sarcoma was investigated by applying the CIBERSORT algorithm to FDC sarcomas and non-FDC mesenchymal tumors and demonstrated that FDC sarcomas were enriched in T follicular helper (TFH) and T regulatory (TREG) cell populations, as confirmed in situ by immunohistochemistry. The enrichment in specific T-cell subsets prompted investigating the mRNA expression of the inhibitory immune receptor PD-1 and its ligands PD-L1 and PD-L2, which were found to be significantly upregulated in FDC sarcomas as compared with other mesenchymal tumors, a finding also confirmed in situ. Here, it is demonstrated for the first time the transcriptional relationship of FDC sarcomas with nonmalignant FDCs and their distinction from other mesenchymal tumors. Implications: The current study provides evidence of a peculiar immune microenvironment associated with FDC sarcomas that may have clinical utility. Mol Cancer Res; 15(5); 541–52. ©2017 AACR.

// Luisa Lorenzi 1 , Claudia Doring 2 , Tobias Rausch 3 , Vladimir Benes 3 , Silvia Lonardi 1 , Mattia Bugatti 1 , Elias Campo 4 , Jose Cabecadas 5 , Ingrid Simonitsch-Klupp 6 , Anita Borges 7 , Jay Mehta 7 , Claudio Agostinelli 8 , Stefano Aldo Pileri 8, 9 , Fabio Facchetti 1 , Martin-Leo Hansmann 2 , Sylvia Hartmann 2 1 Pathology Unit, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy 2 Dr. Senckenberg Institute of Pathology, Goethe University, Frankfurt am Main, Germany 3 Genecore, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany 4 Haematopathology Section, Hospital Clinic, IDIBAPS, University of Barcelona, Barcelona, Spain 5 Department of Pathology, Portuguese Institute of Oncology, Lisbon, Portugal 6 Institute of Pathology, Medical University of Vienna, Vienna, Austria 7 Histopathology, SRL Diagnostics, Mumbai, India 8 Department of Experimental, Diagnostic and Specialty Medicine, Haematopathology Section, S. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy 9 Unit of Diagnostic Haematopathology, European Institute of Oncology, Milan, Italy Correspondence to: Luisa Lorenzi, email: lorenziluisa@gmail.com Keywords: follicular dendritic cell sarcoma, whole transcriptome sequencing, immunohistochemistry, follicular dendritic cell-secreted protein, serglycin Received: September 16, 2016 Accepted: January 17, 2017 Published: January 27, 2017 ABSTRACT Follicular dendritic cell (FDC)-sarcoma is a rare neoplasm with morphologic and phenotypic features of FDCs. It shows an extremely heterogeneous morphology, therefore, its diagnosis relys on the phenotype of tumor cells. Aim of the present study was the identification of new specific markers for FDC-sarcoma by whole transcriptome sequencing (WTS). Candidate markers were selected based on gene expression level and biological function. Immunohistochemistry was performed on reactive tonsils, on 22 cases of FDC-sarcomas and 214 control cases including 114 carcinomas, 87 soft tissue tumors, 5 melanomas, 5 thymomas and 3 interdigitating dendritic cell sarcomas. FDC secreted protein (FDCSP) and Serglycin (SRGN) proved to be specific markers of FDC and related tumor. They showed better specificity and sensitivity values than some well known markers used in FDC sarcoma diagnosis (specificity: 98.6%, and 100%, respectively; sensitivity: 72.73% and 68.18%, respectively). In our cohorts CXCL13, CD21, CD35, FDCSP and SRGN were the best markers for FDC-sarcoma diagnosis and could discriminate 21/22 FDC sarcomas from other mesenchymal tumors by linear discriminant analysis. In summary, by WTS we identified two novel FDC markers and by the analysis of a wide cohort of cases and controls we propose an efficient marker panel for the diagnosis of this rare and enigmatic tumor.

Polycythemia Vera (PV) is a chronic myeloproliferative neoplasm characterized by erythrocytosis, constitutively active mutations in JAK2 and an increased susceptibility to thrombotic events (TEs). There is still controversy about the role of increased hematocrit and of other variables including elevated white blood cell count as risk factors for the occurrence of TEs. A better definition of the relative prognostic importance of hematologic parameters would help us to better tailor the therapeutic approach to PV patients (pts), which is currently mainly based on the use of acetilsalycilic acid (ASA), venesection and hydroxyurea . The aim of our study was to analyze if any clinical or laboratory variables were significantly associated to the occurrence of TEs both at PV diagnosis and during the course of the disease in a large series of PV pts uniformly followed at a single Center over a period of 29.5 years from January 1986 to June 2019. Clinical and laboratory data were obtained from the time of diagnosis until death, progression to acute leukemia or last follow-up. Hematocrit (Hct), hemoglobin (Hb), white blood cell (WBC) and platelet (PLT) levels were recorded for each patient at least every 6 months. Among a total of 331 pts, the median age was 65 years (range 30-92 years), and 56% were male. "High risk" features (age ≥ 60 years and/or history of prior thrombosis) were present in 221 pts (66.7%). The incidence of cardiovascular risk factors was: hypertension 64%, diabetes 15%, hyperlipidemia 28%, history of active or remote smoking 41%. Patients on ASA were 279 (84%), 19 (6%) were on oral anticoagulation, while 27 (8%) were on ASA+oral anticoagulant. At PV diagnosis 54 pts (16%) presented with thrombosis, arterial in 32 (59%) and venous in 22 (41%). A previous TE was recorded in 57 pts (17%): in 43 (75%) arterial, in 12 (22%) venous and in 2 (3%) mixed (arterial+venous). Previous thrombosis was the only variable significantly associated with the presence of a TE at PV diagnosis (P=0.02). After PV diagnosis, with a median follow-up of 81 months (range 1-374 months), 63 pts (19%) experienced a TE and 11 of them a further episode, for a total of 74 TEs. The incidence rate (pts/year) of TEs was 2.7%. Forty-two events were arterial (57%), 31 were venous (42%) and 1 (1%) was mixed. It was the first TE for 37 pts. Cerebrovascular accidents and deep-venous thrombosis were the most frequent arterial and venous TEs both at PV diagnosis and throughout the disease course, with a relative incidence of 50% and 32% respectively. The table compares the characteristics of patients who did or did not develop a TE after PV diagnosis. At univariate analysis, PV high risk status, a previous TE and hyperlipidemia at PV diagnosis were significantly associated with a subsequent TE. Among hematologic variables an elevated WBC count at the time of thrombosis, but not Hct or PLT levels, was highly significantly associated with the development of a TE. At multivariate analysis, WBC count ≥10.4 x 10^9/L and hyperlipidemia maintained their independent prognostic value, while high risk status and a previous TE lost their prognostic significance. Both at univariate and multivariate analysis, hyperlipidemia at diagnosis (P=0.009 and P=0.002) and high WBC count at thrombosis (P=0.001 and P= In conclusion, our analysis confirms that elevated WBC count at the moment of the event more than increased hematocrit is associated to the development of thrombosis in PV pts. We also found that hyperlipidemia was an independent risk factor for arterial thrombosis, calling for an accurate management of increased lipid levels. Whether a reduction of the WBC count during the course of PV may reduce the frequency of TE remains to be demonstrated by prospective studies. Table Disclosures D'Adda: Novartis: Other: Advisory board; Incyte: Other: Advisory board; Pfizer: Other: Advisory board. Rossi:Daiichi Sankyo: Consultancy, Honoraria; Sanofi: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: Advisory board; Alexion: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Jazz: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees.

Introduction: We have previously reported short-term efficacy of six courses of R-DA-EPOCH in patients with aggressive B cell lymphomas carrying concomitant MYC and BCL-2 and/or BCL-6 rearrangement (DHL/THL) or gene increase copy number (ICN) (Tucci et al. Blood S1: 4154, 2017). Further experience with the same program has been described in the meantime in patients with aggressive lymphoma and c-MYC rearrangement, either as single hit or DHL/THL (Dunleavy et al. Lancet Haematol, 2018). We report here long-term results in a larger unselected series of DHL/THL with the aim to confirm our preliminary results and to define the role of consolidation with autologous stem cell transplantation (ASCT) after R-DA-EPOCH remission induction. Methods: The study includes patients consecutively seen in four Italian centres. From January 2014, fit patients aged less than 80 years, with diffuse large B cell lymphoma (DLBCL), lymphoma with intermediate features between DLBCL and Burkitt (BCLU) or high grade lymphoma (HGBCL) histology, diagnosed as DHL or THL by fluorescent in situ hybridization (FISH), were treated with R-DA-EPOCH and central nervous system prophylaxis. Patients with MYC -ICN (three or more extra signals in more than 30% of nuclei, Schieppati et al. Haematologica, 2019) plus BCL-2 and/or BCL-6 gene rearrangement or ICN were also included. Pre-treatment with one cycle of R-CHOP was allowed in patients in need of urgent treatment, pending the results of FISH analysis. Consolidation with ASCT was planned in three of the four centres for stage II-IV patients aged less than 71 who reached at least a partial remission (PR) after six R-DA-EPOCH courses. Immunohistochemistry (IHC) was used to define cell of origin (COO) according to Hans' algorithm, double expressor cases (MYC and BCL-2 protein >40% and 50% respectively) and Ki67 expression. Results: Sixty-three patients were treated (51 DLBCL, 5 BCLU, 7 HGBCL, including 16 with histologic transformation from an indolent lymphoma). Their median age was 63 years (range 23-79) and 43 (68%) were males. Fifty-four (86%) had Ann-Arbor stage III/IV, 18 (28%) B symptoms and 41 (65%) high-intermediate/high risk score according to International Prognostic Index (IPI), with extranodal disease in 79% of patients, mainly in bone and gastrointestinal tract. According to FISH analysis, 34 cases were DHL, 10 THL and 19 c-MYC-ICN. According to IHC, 81% were of germinal center origin, 73% were double expressors and median Ki-67 was 91% (range 35-100%). Patients received a median of six courses of R-DA-EPOCH (range 1-6). Twelve patients were pre-treated with one R-CHOP course and 24 patients (17 in complete remission, 6 in PR and 1 with disease progression) received transplant consolidation (allogeneic SCT in one PR patient), according to the policy of the centre and eligibility criteria. In the entire cohort, the overall response rate was 81%, including 68% complete responses (CR) and 3y-PFS and OS were 67% and 69% respectively. Two patients died of infectious complications during chemotherapy. Of the 10 chemo-refractory patients, all have died of lymphoma. Median length of follow-up was 32 months. At univariate analysis, IPI > 3 and THL were significantly associated with a worse outcome while cMYC-ICN and ASCT with a better OS. At multivariate analysis, only ASCT remained significantly associated with better survival (HR 0.146, IC 95% 0.032-0.667, p 0.013). Focusing on patients who achieved CR with R-DA-EPOCH, all 17 patients who underwent transplantation (100%) are alive (after a median of 27 months from transplant), versus 19 out of 24 patients (79%) who did not. Only one patient relapsed after ASCT and is alive after receiving CAR-T cells. 3y-OS and PFS of patients in CR after induction therapy who received or not ASCT consolidation were 100% vs 76% and 94% vs 72% respectively (Fig.1). Clinical characteristics of the two subgroups were similar except for median age that was lower in the former one (59 vs 69 years). Conclusions: These results confirm the favourable outcome of patients with MYC and BCL-2 and/or BCL-6 rearrangements or gene ICN with R-DA-EPOCH therapy. The role of consolidative ASCT and its usefulness seems encouraging, but remains to be proven by prospective randomized studies. The poor outcome of chemo-refractory patients represents an unmet need and greater expansion of CAR-T cell programs could improve these results in the near future. Disclosures Tucci: Amgen: Consultancy. Carlo-Stella:Boehringer Ingelheim and Sanofi: Consultancy; Servier, Novartis, Genenta Science srl, ADC Therapeutics, F. Hoffmann-La Roche, Karyopharm, Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb, Merck Sharp & Dohme, Janssen Oncology, AstraZeneca: Honoraria; ADC Therapeutics and Rhizen Pharmaceuticals: Research Funding. Corradini:Takeda: Consultancy, Honoraria, Other; BMS: Other; Janssen: Consultancy, Honoraria; Kite: Consultancy, Honoraria; KiowaKirin: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Other: Travel and accommodations paid by for; F. Hoffman-La Roche Ltd: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Servier: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Other: Travel and accommodations paid by for; Amgen: Consultancy, Honoraria, Other: Travel and accommodations paid by for; Daiichi Sankyo: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Other: Travel and accommodations paid by for; Incyte: Consultancy; AbbVie: Consultancy, Honoraria, Other: Travel and accommodations paid by for. Rossi:Janssen: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Other: Advisory board; Abbvie: Membership on an entity's Board of Directors or advisory committees; Alexion: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria; Jazz: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria.

A limited number of sclerosing Angiomatoid Nodular Transformation (SANT) have been reported in pediatric age. We describe the first case of SANT occurring in a nine-week-old female infant that was admitted to our unit for severe abdominal distension and rectal bleeding. Enlarged spleen was detected on physical examination. Laboratory investigations revealed severe anemia and coagulation abnormalities. Abdominal ultrasound and computed tomography revealed ascites and splenomegaly with a large mass at the lower medial splenic pole. A diagnosis of intraabdominal hemorrhage was presumed and an exploratory laparotomy was performed. A complete transformation of the giant splenomegaly to bossellated masses and multiple bleeding capsular ruptures without subcapsular hematoma were found and an urgent splenectomy was performed. At histology, a SANT was diagnosed (CD34, CD31, CD8 positivity). The postoperative follow up was uneventful. SANT may also occur in infancy with a potentially lifethreatening presentation. Splenectomy may represent the only treatment in severe cases.

Germinotropic lymphoproliferative disorders were previously described as localized disorders associated with coinfection by human herpes virus 8 and Epstein-Barr virus and characterized by good clinical outcome. We report the clinical, morphological, phenotypical, and molecular features of three cases of a hitherto unreported variant of Epstein-Barr virus (EBV)-positive, human herpes virus 8 (HHV8)-negative large B cell lymphoma with exclusive intrafollicular localization. All cases occurred in elderly individuals (63, 77, and 65 years old; one male, two females) without obvious immunedeficiency, who presented with high stage disease. Lymph nodes showed an effaced nodular architecture with abnormal B follicles colonized by EBV+ large, pleomorphic atypical cells, including Reed-Sternberg-like cells, showing an activated B cell phenotype (CD10-FOXP1-Bcl6-IRF4+ or CD10-FOXP1+Bcl6+IRF4+) and intense expression of CD30. No monoclonal light-chain restriction was detected by immunohistochemistry or in situ hybridization, and IGH rearrangement was polyclonal; notably, EBV clonality was detectable in one case. Lymphoma cells in all cases showed diffuse expression of the c-Myc protein, while Bcl2 was dim or negative; moreover, the strong expression of phosphorylated-STAT3 in tumor cell nuclei suggested activation of the JAK-STAT pathway. FISH analysis was performed in two cases and showed no translocations of BCL2, BCL6, MYC, and PAX5 genes. Response to treatment was poor in 2/3 patients: one died after 18 months, one is alive with disease after 12 months. The intrafollicular EBV-positive large B cell lymphoma expands the spectrum of EBV-associated lymphoproliferative disorders in immunocompetent individuals.

Aim of the current study was to evaluate the inter-observer agreement between pathologists in the diagnosis of celiac disease (CD), in the qualified context of a multicenter study. Biopsies from the “PreventCD” study, a multinational- prospective- randomized study in children with at least one-first-degree relative with CD and positive for HLA-DQ2/HLA-DQ8. Ninety-eight biopsies were evaluated. Considering diagnostic samples with villous atrophy (VA), the agreement was satisfactory (κ = 0.84), but much less when assessing the severity of these lesions. The use of the recently proposed Corazza-Villanacci classification showed a moderately higher level of agreement (κ = 0.39) than using the Marsh-Oberhuber system (κ = 0.31). 57.1% of cases were considered correctly oriented. A number of >4 samples per patient was statistically associated to a better agreement; orientation did not impact on κ values. Agreement results in this study appear more satisfactory than in previous papers and this is justified by the involvement of centers with experience in CD diagnosis and by the well-controlled setting. Despite this, the reproducibility was far from optimal with a poor agreement in grading the severity of VA. Our results stress the need of a minimum of four samples to be assessed by the pathologist.

BACKGROUND There are few studies in the literature correlating the ultrasonographic findings, clinical scoring systems or histological findings in morphoea after ultraviolet (UV)A1 phototherapy. AIMS To evaluate the quantitative and morphological aspects of high-frequency ultrasonography in the treatment of plaque morphoea in response to UVA1 phototherapy, and to correlate these with clinical and histological scores. METHODS In total, 17 patients with morphoea were studied. Initially and at study end, high-frequency ultrasonography (50 MHz) was performed on the edge of a morphoea lesion treated with UVA1 phototherapy. A quantitative and qualitative analysis of dermal features was performed and compared with the features of healthy skin. Skin biopsy specimens were obtained from lesions analysed at the beginning and end of the study, assessing dermal sclerosis and dermal inflammatory infiltrate and their distribution. RESULTS All affected skin showed a statistically significant increase in dermal thickness and hypoechogenicity, corresponding to a reduction in dermal density by ultrasonography compared with healthy skin. Morphological evaluation identified undulations of the dermis in 11 of 17 lesions (64.7%) and in 5 healthy skin areas (29.4%) (P = 0.08), while 'yoyo' figures were identified in 8 lesions (47%) but only 1 healthy skin area (5.9%) (P = 0.02). Ultrasonographic morphological analysis highlighted an improvement in dermal hyperechogenic bands and disappearance of yoyo figures after UVA1 treatment. Histology revealed a reduction in dermal sclerosis and inflammation, although this was not statistically significant. CONCLUSIONS Ultrasonographic pattern analysis of morphoea is a suitable technique for monitoring UVA1 phototherapy response.

Terminal tissue differentiation and function of slan+ monocytes in cancer is largely unexplored. Our recent studies demonstrated that slan+ monocytes differentiate into a distinct subset of dendritic cells (DC) in human tonsils and that slan+ cells colonize metastatic carcinoma-draining lymph nodes. Herein, we report by retrospective analysis of multi-institutional cohorts that slan+ cells infiltrate various types of non-Hodgkin lymphomas (NHL), particularly the diffuse large B-cell lymphoma (DLBCL) group, including the most aggressive, nodal and extranodal, forms. Nodal slan+ cells displayed features of either immature DC or macrophages, in the latter case ingesting tumor cells and apoptotic bodies. We also found in patients with DLBCL that peripheral blood slan+ monocytes, but not CD14+ monocytes, increased in number and displayed highly efficient rituximab-mediated antibody-dependent cellular cytotoxicity, almost equivalent to that exerted by NK cells. Notably, slan+ monocytes cultured in conditioned medium from nodal DLBCL (DCM) acquired a macrophage-like phenotype, retained CD16 expression, and became very efficient in rituximab-mediated antibody-dependent cellular phagocytosis (ADCP). Macrophages derived from DCM-treated CD14+ monocytes performed very efficient rituximab-mediated ADCP, however, using different FcγRs from those used by slan+ macrophages. Our observations shed new light on the complexity of the immune microenvironment of DLBCL and demonstrate plasticity of slan+ monocytes homing to cancer tissues. Altogether, data identify slan+ monocytes and macrophages as prominent effectors of antibody-mediated tumor cell targeting in patients with DLBCL. Significance: slan+ monocytes differentiate into macrophages that function as prominent effectors of antibody-mediated tumor cell targeting in lymphoma. Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/13/3544/F1.large.jpg. Cancer Res; 78(13); 3544–59. ©2018 AACR.

Mesenchymal stromal cells (MSCs) exert immunosuppressive effects on immune cells including dendritic cells (DCs). However, many details of the bidirectional interaction of MSCs with DCs are still unsolved and information on key molecules by which DCs can modulate MSC functions is limited. Here, we report that osteopontin (OPN), a cytokine involved in homeostatic and pathophysiologic responses, is constitutively expressed by DCs and regulated in the DC/MSC cocultures depending on the activation state of MSCs. Resting MSCs promoted OPN production, whereas the production of OPN was suppressed when MSCs were activated by proinflammatory cytokines (i.e., TNF-α, IL-6, and IL-1β). OPN induction required cell-to-cell contact, mediated at least in part, by β1 integrin (CD29). Conversely, activated MSCs inhibited the release of OPN via the production of soluble factors with a major role played by Prostaglandin E2 (PGE2). Accordingly, pretreatment with indomethacin significantly abrogated the MSC-mediated suppression of OPN while the direct addition of exogenous PGE2 inhibited OPN production by DCs. Furthermore, DC-conditioned medium promoted osteogenic differentiation of MSCs with a concomitant inhibition of adipogenesis. These effects were paralleled by the repression of the adipogenic markers PPARγ, adiponectin, and FABP4, and induction of the osteogenic markers alkaline phosphatase, RUNX2, and of the bone-anabolic chemokine CCL5. Notably, blocking OPN activity with RGD peptides or with an antibody against CD29, one of the OPN receptors, prevented the effects of DC-conditioned medium on MSC differentiation and CCL5 induction. Because MSCs have a key role in maintenance of bone marrow (BM) hematopoietic stem cell niche through reciprocal regulation with immune cells, we investigated the possible MSC/DC interaction in human BM by immunohistochemistry. Although DCs (CD1c+) are a small percentage of BM cells, we demonstrated colocalization of CD271+ MSCs with CD1c+ DCs in normal and myelodysplastic BM. OPN reactivity was observed in occasional CD1c+ cells in the proximity of CD271+ MSCs. Altogether, these results candidate OPN as a signal modulated by MSCs according to their activation status and involved in DC regulation of MSC differentiation.

Terminal tissue differentiation and function of slan

BACKGROUND Polymorphic light eruption (PLE) is the most common autoimmune photodermatosis. Plasmacytoid dendritic cells (PDCs) are important mediators of innate antimicrobial immunity involved in the pathogenesis of many inflammatory skin diseases. In addition to PDCs, regulatory T cells (Tregs) are involved in controlling inflammation and adaptive immunity in skin by their immunosuppressive capacity. OBJECTIVE The aim of this study was to investigate the presence of PDCs and Tregs in photoexposed skin from PLE compared to healthy skin. METHODS Patients with PLE diagnosis and healthy controls were recruited and underwent a photoprovocative test. A 4-mm punch biopsy was taken from the site of positive photoprovocation test reaction, and immunohistochemistry for BDCA2 as marker for PDCs, CD4 and FOXP3 as markers for Tregs was performed. Double immunostain for FOXP3 and CD4 was performed as well. Absolute counts for CD4, BDCA2 and FOXP3 were performed in at least 5 High Power Fields (HPF). Percentage of CD4-, BDCA2- and CD4FOXP3-positive cells over the total inflammatory infiltrate was assessed for each case. RESULTS We enrolled 23 patients and controls. BDCA2+ cells were present in 91.3% of PLE skin samples and 100% of healthy volunteer. Both in PLE patients and healthy controls, PDCs distribution was mainly dermic (P < 0.05). Compared to healthy controls, both epidermic and dermic BDCA2+ cells count were significantly higher in PLE patients (P < 0.05). Both in PLE patients and healthy controls, Tregs distribution was mainly dermic (P < 0.05). The presence of both CD4+ cells and FOXP3+ cells was significantly higher in the dermis of PLE patients compared to controls (P < 0.05). Relative percentages of cellular infiltrations confirmed these results. CONCLUSIONS D-PDCS and Tregs may play a significant role in the development of PLE, and dermal distribution of PDCs in PLE skin biopsies seems to confirm a possible overlap with cutaneous lupus erythematosus (CLE).

Background & Aims Mucosal healing, determined by endoscopic evaluation, is one of the most important prognostic markers for patients with inflammatory bowel diseases. Findings from histologic evaluation, however, could complement findings from endoscopy in assessing mucosal responses to treatment. We analyzed long-term results of children treated with thalidomide to determine the association between clinical response and histology and endoscopy findings. Methods We collected data from 2 multicenter trials of 70 children with refractory Crohn's disease (CD) or ulcerative colitis (UC) (2–18 years old; ileocolonic or colonic disease) given thalidomide or placebo (NCT00720538). Clinical remission and clinical response at 8 weeks were defined as a pediatric CD activity index scores 10 points or lower and a decrease of at least 50% from baseline, respectively, for patients with CD; and as a pediatric UC activity index score below 10 and a decrease of at least 20 points from baseline, respectively, for patients with UC. Patients with a clinical response to 8 weeks' treatment with thalidomide underwent endoscopic examination with biopsy collection at study weeks 12 and 52. Severity of inflammation in patients with UC was assessed by Mayo score and in patients with CD by 4-grade system. Biopsies were assessed for signs of active inflammation, erosion or ulceration, and crypt abscesses and assigned a histologic score. Results Clinical remission was observed in 42 patients (60.0%) and clinical response in 45 patients (64.2%) at Week 8. At Week 52, a total of 38 patients (54.3%) were still in clinical remission or still had a clinical response; 29 patients (41.4%) had mucosal healing, defined as complete healing of erosions or ulcerations, and 20 patients (27.7%) had histologic healing, defined as complete absence of markers of inflammation. Of patients with clinical remission or clinical response, 75.3% also had mucosal healing and 52.6% also had histologic healing. The probability of achieving mucosal healing decreased significantly with increasing values of erythrocyte sedimentation rate (adjusted odds ratio, 0.96; 95% CI, 0.93–0.98; P = .006). Conclusions In a long-term analysis of data from 2 clinical trials of pediatric patients with CD or UC, 52 weeks' treatment with thalidomide led to clinical remission in 54.3% of patients with ileocolonic or colonic disease; of these patients, 75.3% had mucosal healing and 52.6% also had histologic healing. Further studies are needed to determine how thalidomide therapy affects long-term progression of inflammatory bowel diseases. (ClinicalTrials.gov number NCT00720538).

Tumors derived from histiocytic and dendritic cells encompass a large and heterogeneous group of neoplastic and reactive conditions, and their diagnosis is challenging both for pathologists and clinicians. Diagnosis is based on morphological and phenotypical findings, but hybrid features are not uncommon. Furthermore, recent studies uncovered the molecular mechanisms driving some of these tumors, improving diagnostic adequacy, and providing the basis for effective therapeutic breakthroughs. Sixty-seven cases were submitted to the accessory cell and histiocytic neoplasms session at the European Association of Haematopathology/Society for Hematopathology workshop 2016 held in Basel, Switzerland. The cases included histiocytic sarcomas (HS), Langerhans cell tumors (LCT), Erdheim-Chester disease, interdigitating dendritic cell sarcomas (IDCS), indeterminate dendritic cell tumors (IND-DCT), follicular dendritic cell sarcomas, and blastic plasmacytoid dendritic cell neoplasms. Rosai-Dorfman disease and, more rare, conditions such as ALK-positive histiocytosis were also submitted. These cases illustrated classical and unexpected features at morphological, phenotypical, and molecular levels, providing a valuable compendium for pathologists confronting with these tumors. The paper summarizes the most notable features of every single group of diseases, with comments about the most challenging issues, in the attempt to provide practical indications for their recognition.

Inflammatory myofibroblastic tumor (IMT) is a locally aggressive neoplasm, most frequently occurring in the abdominal cavity as multiple recurrent nodules. We report a case of IMT in a 24-year-old male presenting as multiple nodules involving the omentum, the liver, and the colon. Spindle tumor cells expressed ALK with a cytoplasmic granular distribution, the CLTC-ALK fusion gene was demonstrated by reverse-transcriptase polymerase chain reaction analysis, and break-apart fluorescence in situ hybridization (FISH) probes for the ALK gene showed a pathological pattern (single red signal associated with 1/2 normal fused signals) highly suggestive for combined gene fusion and deletion. To reduce the surgically unresectable liver mass, the patient was treated with crizotinib, and after 4 months of treatment the disease was defined stable according to RECIST criteria. Interestingly, ALK and FISH/FICTION analysis revealed that tumor cells were widely dispersed as multiple microscopic foci or as single cells beneath the omental mesothelium. These findings indicate that IMT multifocality might result either from dissemination from the main tumor mass or development of multiple independent neoplastic foci; furthermore, they underline the need of omentectomy in abdominal IMT to obtain surgical radicality.

Tetraparesis is usually due to cerebral palsy (CP), inborn errors of metabolism, neurogenetic disorders and spinal cord lesions. However, literature data reported that about 10% of children with tetraparesis show a negative/non-specific neuroradiological findings without a specific etiological cause. Aicardi Goutières Syndrome (AGS) is a genetic encephalopathy that may cause tetraparesis. Interferon signature is a reliable biomarker for AGS and could be performed in sine-causa tetraparesis. The aim of the study was to examine the type I interferon signature and AGS related-genes in children with sine causa tetraparesis, to look for misdiagnosed AGS. A secondary aim was to determine which aspects of the patient history, clinical picture and brain imaging best characterize tetraparesis due to an interferonopathy. Seven out of 78 patients affected by tetraparesis, characterized by unremarkable pre-peri-postnatal history and normal/non-specific brain magnetic resonance imaging (MRI) were selected and underwent anamnestic data collection, clinical examination, brain imaging review, peripheral blood interferon signature and AGS-related genes analysis. At our evaluation time (mean age of 11.9 years), all the 7 patients showed spastic-dystonic tetraparesis. At clinical onset brain MRI was normal in 4 and with non-specific abnormalities in 3; at follow-up 3 patients presented with new white-matter lesions, associated with brain calcification in 1 case. Interferon signature was elevated in one subject who presented also a mutation of the IFIH1 gene. AGS should be considered in sine-causa tetraparesis. Core features of interferonopathy-related tetraparesis are: onset during first year of life, psychomotor regression with tetraparesis evolution, brain white-matter lesions with late calcifications. A positive interferon signature may be a helpful marker to select patients with spastic tetraparesis who should undergo genetic analysis for AGS.

Follicular dendritic cell (FDC) sarcomas are rare mesenchymal tumours, which are fatal in 20% of the patients and usually occur in secondary lymphoid organs or extranodal localizations. Due to the rareness of these tumours, only few studies have been conducted on molecular level. In the present study, we performed microRNA (miRNA) profiling of 31 FDC sarcomas and identified two subgroups, one with high miRNA expression and the other group with low miRNA expression levels. The first group showed a strong similarity to fibroblasts and myopericytomas, whereas the second group was more closely related to FDCs from Castleman's disease. Both groups showed important differences compared with myeloid-derived dendritic cells, confirming mesenchymal origin of FDCs and their derived sarcomas. The two FDC sarcoma groups did not differ on morphological grounds, mitotic activity or BRAF mutation status. However, patients of group I presented a tendency to a shorter overall survival and more frequent podoplanin expression by immunohistochemistry. The importance of these newly recognized FDC sarcoma subgroups in terms of clinical behaviour and therapeutic implications should be assessed in a larger cohort in future studies.

Summary Background Surgical excision represents the most common elective treatment for basal cell carcinoma (BCC). Several noninvasive approaches have been proposed for in vivo determination of tumour margin, in order to achieve radical removal. Objectives To propose a new approach through the combination of dermoscopy and reflectance confocal microscopy (RCM) for lateral margin detection in BCC. Methods Ten patients with lesions clinically suggestive of nonpigmented BCCs with ill-defined margins were enrolled. All BCCs were dermoscopically evaluated first and the ill-defined margins were marked with a superficial cut and then inspected using RCM. Results RCM evaluation showed BCC foci beyond the presurgical marker in three out of 10 lesions. Histology confirmed the RCM results: the presence of BCC features across the cut, corresponding to two superficial BCCs and a morpheaform BCC. Conclusions This new procedure helped to improve the identification of proper margins for surgical excision in nonpigmented BCC with clinically and dermoscopically ill-defined margins.

Follicular dendritic cells are mesenchymal-derived dendritic cells located in the B follicles, where they capture, retain and present antigens to surrounding B cells, thus playing a pivotal role in triggering and maintaining B-cell adaptive immune response. The term follicular dendritic cells (FDC) was originally introduced by Steinman et al. in 1978. In 1986, Monda and Rosai first reported tumoral proliferations derived from FDC occurring in lymph nodes and the term FDC sarcoma was subsequently coined to identify this neoplasm. FDC sarcoma is nowadays a well recognized entity known to involve both nodal and extranodal sites. In this review we summarize data on physiological functions of FDC in the immune response, their involvement in pathological conditions, and the clinical, histopathological and phenotypic features of FDC sarcoma.

Schaumann bodies are inclusion bodies, first described by Schaumann in 1941, typically seen in granulomatous diseases such as tuberculosis, sarcoidosis and chronic beryllium diseases. Williams WJ, in 1964, reported Schaumann bodies to occur in 10% of Crohn's disease (CD). We report a case of Crohn's disease, initially misdiagnosed as a schistosoma-related colitis for the presence of numerous calcified bodies resembling calcified ova and scattered granulomas. Subsequent biopsies showed more typical histological features and, in combination with a more complete clinical history, diagnosis of Crohn's disease was made.

We report three cases of follicular dendritic cell sarcoma (FDCS) showing a hitherto undescribed histological pattern consisting of nodular tumor growth associated with small B lymphocytes. FDCS tumor cells consistently showed large epithelioid features and were intermingled with small lymphocytes in the nodules in two cases, whereas they formed cohesive aggregates surrounded by lymphocyte mantle in the other. These features were easily confused with lymphomatous proliferations and, in particular, subtypes of Hodgkin lymphoma, high-grade follicular lymphoma, and germinotropic large B-cell lymphomas. The diagnosis was established by the use of a broad panel of antibodies that showed a variable expression of the FDC markers CD21, CD23, CD35, clusterin, podoplanin, claudin 4, epidermal growth factor receptor, and CXCL13. The associated B lymphocytes revealed a mantle zone B phenotype, with expression of CD20 and PAX5, together with TCL1 and IgD. Of notice, in all cases, morphological features suggesting hyaline-vascular Castleman disease were recognized in the interfollicular areas, containing scattered epithelioid cells similar to those found in the nodules, thus providing a useful clue for FDCS diagnosis. Of the 3 cases, 1 presented multiple recurrences unresponsive to chemotherapy and radiotherapy and finally died of disease 14 years after diagnosis. This study further emphasizes the extreme variability of morphological presentation of FDCS and expands the spectrum of lesions showing a nodular growth pattern occurring in human lymph nodes.