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Background: Pancreatic ductal adenocarcinoma (PDAC) is characterized by a highly immunosuppressive tumor microenvironment (TME). The aim of this study is to determine the potential significant TME immune markers of long-term survival. Methods: We retrospectively included patients with a diagnosis of resectable PDAC having undergone upfront surgery. Immunohistochemical (IHC) staining using tissue microarray for PD-L1, CD3, CD4, CD8, FOXP3, CD20, iNOS and CD163 was performed in order to characterize the TME. The primary endpoint was long-term survival, defined as the Overall Survival > 24 months from surgery. Results: A total of 38 consecutive patients were included, and 14 (36%) of them were long-term survivors. Long-term survivors showed a higher density of CD8+ lymphocytes intra- and peri-acinar (p = 0.08), and a higher CD8/FOXP3 intra- and peri-tumoral ratio (p = 0.05). A low density of intra- and peri-tumoral FOXP3 infiltration is a good predictor of long-term survival (p = 0.04). A significant association of the low density of intra- and peri-tumoral tumor-associated macrophages (TAMs) iNOS+ with long-term survival was detected (p = 0.04). Conclusions: Despite the retrospective nature and small sample size, our study showed that the high infiltration of CD8+ lymphocytes and low infiltration of FOXP3+ and TAMs iNOS+ are predictors of good prognosis. A preoperative assessment of these potential immune markers could be useful and determinant in the staging process and in PDAC management.

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Purpose:BRAF mutations are grouped in activating RAS-independent signaling as monomers (class 1–V600E) or as dimers (class 2–codons 597/601), and RAS-dependent with impaired kinase activity (class 3–codons 594/596). Although clinical, pathologic, and molecular features of V600EBRAF-mutated metastatic colorectal cancer (mCRC) are well known, limited data are available from the two other classes.Experimental Design:Data from 117 patients with BRAF (92 class 1, 12 class 2, and 13 class 3)-mutated mCRC were collected. A total of 540 BRAF wt mCRCs were included as control. IHC profiling was performed to determine the consensus molecular subtypes (CMS), cytokeratin 7/20 profiles, tumor-infiltrating lymphocyte infiltration, and BM1/BM2 categorization. Overall survival (OS) and progression-free survival were evaluated by Kaplan–Meier and log-rank test.Results:Class 3 BRAF-mutated mCRC was more frequently left sided (P = 0.0028), pN0 (P = 0.0159), and without peritoneal metastases (P = 0.0176) compared with class 1, whereas class 2 cases were similar to class 1. Hazard ratio for OS, as compared with BRAF wt, was 2.38 [95% confidence interval (CI), 1.61–3.54] for class 1, 1.90 (95% CI, 0.85–4.26) for class 2, and 0.93 (95% CI, 0.51–1.69) for class 3 (P < 0.0001). Class 2 and 3 tumors were all assigned to CMS2-3. A higher median CD3/CD8-positive lymphocyte infiltration was observed in BRAF-mutated class 2 (P = 0.033) compared with class 3 cases.Conclusions:For the first time, different clinical and pathologic features and outcome data were reported according to the three BRAF mutation classes in mCRC. Specific targeted treatment strategies should be identified in the near future for such patients.

Colorectal adenosquamous carcinoma (ASC) is exceedingly rare, comprising less than 0.1% of all colorectal malignancies, and is characterized by an aggressive disease course, with a higher metastatic rate and worse outcome than conventional colorectal adenocarcinoma. A comprehensive molecular profile of this group of neoplasms is still lacking. A total of 22 cases of colorectal ASCs (with 22 primary lesions and 7 metastases matched with 4 primaries) were subject to NGS targeting 67 cancer-related genes (VariantPlex solid tumor; Archer). Mismatch repair (MMR), p53, and V600EBRAF status were also investigated by immunohistochemistry. In 28 of 29 (96.6%) ASC samples, at least one single-nucleotide variant (SNV) or copy number variation (CNV) was detected. Among the 22 primary tumors, the most frequently mutated genes were TP53 (59.1%), APC (40.9%), KRAS (27.3%), BRAF (13.6%), and GNAS (9.1%). Only 1/22 (4.5%) primary ASC was MMR-deficient (MMRd) and harbored a BRAF mutation. Limited differences in SNVs were observed between primary and metastatic diseases. This study sheds light on the molecular landscape of colorectal ASCs. According to our data, the genomic profile of colorectal ASC is similar to that of conventional colorectal carcinoma, with significant druggable genetic alterations. Further studies are required to understand the more aggressive clinical behavior of this neoplasm.

The inability to efficiently repair DNA double-strand breaks using the homologous recombination repair pathway is defined as homologous recombination deficiency (HRD). This molecular phenotype represents a positive predictive biomarker for the clinical use of poly (adenosine diphosphate [ADP]-ribose) polymerase inhibitors and platinum-based chemotherapy in ovarian cancers. However, HRD is a complex genomic signature, and different methods of analysis have been developed to introduce HRD testing in the clinical setting. This review describes the technical aspects and challenges related to HRD testing in ovarian cancer and outlines the potential pitfalls and challenges that can be encountered in HRD diagnostics.

AimsPoly (ADP-ribose) polymerase (PARP) inhibitors (PARPIs) represent a standard of care for the clinical management of high-grade serous ovarian cancer (HGSOC). The recognition of homologous recombination deficiency (HRD) has emerged as a predictive biomarker of response for first-line PARPIs treatment in patients with HGOSC. On the other hand, this test is extremely complex and therefore it is often externalised. Regrettably, the reliability of outsourced HRD testing can be troubled by inconclusive results and high rejection rates. In this methodological study, we assessed the technical feasibility, interassay and interlaboratory reproducibility of in-house HRD testing using three different commercially available next-generation sequencing assays.MethodsA total of n=20 epithelial ovarian cancer samples previously analysed with MyChoice CDx were subjected to HRD retesting using three different platforms in three different major pathology laboratories, that is, SOPHiA DDM HRD Solution, HRD focus and Oncomine homologous recombination repair pathway predesigned panel. Concordance was calculated by Cohen’s (dual) and Fleiss (triple) κ coefficients.ResultsIn-houseBRCA1/2molecular testing yielded a concordance rate >90.0% among all participating centres. HRD scores were successfully calculated by each institution with a concordance rate of 76.5%. Concerning the external gold standard test, the overall percentage of agreement ranged from 80.0% to 90.0% with a positive percentage agreement ranging from 75.0% to 80.0% and a negative percentage agreement ranging from 80.0% to 100%.ConclusionsIn-house testing for HRD can be reliably performed with commercially available next-generation sequencing assays.

Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous malignant tumor with neuroendocrine differentiation, with a rapidly growing incidence rate, high risk of recurrence, and aggressive behavior. The available therapeutic options for advanced disease are limited and there is a pressing need for new treatments. Tumors harboring fusions involving one of the neurotrophin receptor tyrosine kinase (NTRK) genes are now actionable with targeted inhibitors. NTRK-fused genes have been identified in neuroendocrine tumors of other sites; thus, a series of 76 MCCs were firstly analyzed with pan-TRK immunohistochemistry and the positive ones with real-time RT-PCR, RNA-based NGS, and FISH to detect the eventual underlying gene fusion. Despite 34 MCCs showing pan-TRK expression, NTRK fusions were not found in any cases. As in other tumors with neural differentiation, TRK expression seems to be physiological and not caused by gene fusions.

We aimed to explore the activation of monoacylglycerol lipase (MAGL)/cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) axis in hepatocellular carcinoma (HCC), evaluating circulating PGE2 as prognostic biomarker in HCC patients. PGE2 levels were measured in blood samples from 24 cirrhotics, and 34 HCC patients were consecutively collected between January 2016 and December 2017. In a subgroup of patients, tissue expression of MAGL mRNA and immunohistochemistry for MAGL and COX-2 were obtained. Despite tumor tissues showing overexpression of MAGL mRNA and higher levels of both MAGL and COX-2 at immunohistochemistry, PGE2 levels were not significantly different in HCC and cirrhotics. HCC patients with circulating PGE2 levels > 14 pg/mL had a significantly shorter overall survival (19.4 vs. 49.9 months; p = 0.03), the finding being confirmed by the multivariate analysis (HR 3.37 [95% CI 1.00–11.60]; p = 0.05). The MAGL/COX-2/PGE2 axis is activated in HCC, and circulating PGE2 proved to be a potential prognostic biomarker.

Background: Peritoneal dissemination represents a poor prognostic indicator in gastric cancer. Despite a comprehensive molecular characterization of this disease, no peritoneal dissemination-specific signature has been identified, limiting the tailoring of the surgical and oncological treatments. In this review, we outline the available literature focusing on the role of the different molecular pathways involved in the acquisition of peritoneal metastatic dissemination. Summary: According to our results, several molecular determinants are associated with peritoneal carcinomatosis and are involved in several cellular and molecular carcinogenetic processes. However, a comprehensive understanding of the complex molecular landscape of gastric carcinosis is still lacking. Key Messages: More efforts should be made toward the integration of molecular and histologic data to perform a risk prediction assessment of peritoneal dissemination based on molecular profiling and histological evaluation.

Background: Both the prevalence of sinonasal inverted papilloma (IP) and the causal association with alpha-human papillomaviruses (alpha-HPVs) are controversial. In this study we aimed to determine HPV status in histologically selected, microdissected, formalin-fixed, and paraffin-embedded tissue samples of IP. Methods: HPV status was assessed retrospectively by polymerase chain reaction (PCR)-bead‒based multiplex genotyping on tissue samples of patients diagnosed with IP and consecutively treated with endoscopic resection. Forty-one HPV genotypes were considered, distinguishing between high risk and low risk. HPV status was correlated with demographics and clinical variables. Sixty sinonasal IP tissue samples were initially considered. After exclusion of 5 cases due to insufficient quality/quantity of the samples, 55 patients were included for analysis. Results: HPV-DNA sequences were identified in 34 of 55 (61.8%) IPs, with a higher prevalence of high-risk than low-risk HPV genotypes (19 [55.9%] and 15 cases [44.1%], respectively). HPV16 strongly prevailed among the high-risk HPV cases (84.2%), and HPV54 prevailed among the low-risk HPV cases (53.3%). IPs with origin within the maxillary sinus were significantly associated with high-risk HPV (p = 0.019). No significant associations emerged between HPV status and demographics or clinical variables. Conclusion: In a series of 55 IP tissue samples, HPV-DNA sequences were identified in 61.8% of cases, which differs from the data of previous investigations. Further case-control studies are advocated to confirm this prevalence in the Italian population addressed, and also to clarify any pathogenic involvement of HPV in the natural history of IPs.

218 Background: Immune checkpoint inhibitors (ICI) showed high efficacy in both first and subsequent lines in metastatic colorectal cancer with mismatch repair deficiency (dMMR-mCRC); however, they still fail in a minority of patients (pts). In non-preplanned analyses from previous studies, RAS mutations ( RASm) have been related to limited activity of ICI monotherapy (ICIm) as compared to ICI doublets (ICId) in dMMR-mCRC. Emerging data suggest different immunological features in presence of RASm, resulting in lower immunogenicity. Methods: NERDY is a retrospective, monocentric study designed to investigate the effect of ICIm and ICId on dMMR-mCRC basing on RASm. Pts with dMMR-mCRC treated with ICIm/ICId at our Institute were included. Clinical-pathological features for each patient were collected. On primary tumor specimens, proinflammatory pathways and CMS subgroup will be assessed by Nanostring and RNA-Seq respectively. The study is exploratory and no formal hypothesis has been postulated. Both PFS and OS were calculated with Kaplan-Meier. Cox proportional hazard model was adopted in the interaction tests. Primary objective was to assess OS and PFS according to RAS in dMMR-mCRC pts treated with ICIm or ICId. Secondary objectives were to describe the inflammatory infiltrate and TMB in dMMR-mCRC according to RAS status. Results: From June 2015 to January 2022, a total of 126 consecutive dMMR-mCRC pts treated with ICI were included, 33 RASm/93 RASwt. RASm pts were more frequently males (p=0.015) and younger (median age 47 vs 65). An imbalance was observed in sidedness (more right-CRC in RASwt than in RASm as BRAF effect, p=0.001) and timing of ICI (administered in later lines in RASm, p=0.013). No differences in ECOG-PS, histotype, disease burden, stage at diagnosis, treatment with ICIm vs ICId and best response. At a median follow up of 53.5 months (95%CI 34.7-56.9), a trend toward longer PFS in pts treated with ICId over ICIm was found in the overall population (HR 0.62; 95%CI 0.36-1.05; p=0.055), being significantly longer in RASm-only pts (HR 0.41; 95%CI 0.13-1.28; p=0.047) but not in RASwt-only pts (HR 0.64; 95%CI 0.34-1.20; p=0.139). No difference was observed in OS between ICId and ICIm in the overall population (HR 0.64; 95%CI 0.36-1.16; p=0.121), in RASwt (HR 0.59; 95%CI 0.29-1.20; p=0.132) nor in RASm pts (HR 0.59; 95%CI 0.19-1.78; p=0.275). Interaction test for RAS and ICI treatment type was not significant for PFS (HR 0.63; 95%CI 0.21-1.94; p=0.423) nor for OS (HR=1.00; 95%CI 0.29-3.41; p=0.999). Conclusions: Preliminary clinical results of the NERDY study suggest enhanced activity of ICId compared to ICIm in pts with RASm dMMR-mCRC. Further data are expected from pending translational analyses and a pre-planned adjunctive cohort from two other Italian centers will be used for external validation.

The introduction of next-generation sequencing (NGS) in the molecular diagnostic armamentarium is deeply changing pathology practice and laboratory frameworks. NGS allows for the comprehensive molecular characterization of neoplasms, in order to provide the best treatment to oncologic patients. On the other hand, NGS raises technical issues and poses several challenges in terms of education, infrastructures and costs. The aim of this review is to give an overview of the main NGS sequencing platforms that can be used in current molecular diagnostics and gain insights into the clinical applications of NGS in precision oncology. Hence, we also focus on the preanalytical, analytical and interpretative issues raised by the incorporation of NGS in routine pathology diagnostics.

In sessile serrated lesions (SSLs) with adenomatous dysplasia, the dysplastic component and the serrated component without dysplasia should be considered as part of the same lesion, classified as SSL with dysplasia. However, some of these lesions may actually represent collisions between a serrated polyp and a conventional adenoma. Further supporting the "collision theory", conventional adenomatous dysplasia may be found in association with hyperplastic polyps (HPs). In order to determine the molecular and biological landscape of conventional type dysplasia in serrated lesions, we collected 17 cases of colorectal serrated lesions with adenomatous dysplasia, classifying them as SSL with dysplasia (n = 10) or as mixed lesions comprising a HP component and a conventional adenomatous component (n = 7). We characterized the dysplastic and the non-dysplastic component of each lesion, after microdissection, through the targeted mutational analysis of 11 commonly altered genes in colorectal cancer (AKT1, APC, BRAF, CTNNB1, KIT, KRAS, NRAS, PDGFRA, PIK3CA, PTEN and TP53). We also characterized MMR and p53 status by immunohistochemistry. Overall, 14/17 (82.4 %) cases harbored a mutation in at least one of the two components. The most altered genes were BRAF in 10/17 (58.8 %) cases, APC in 2/17 (11.8 %) and TP53 in 4/17 (23.5 %). Among the SSL with dysplasia, the mutational profile was concordant between the two components in 7/10 (70 %) cases, while among the mixed lesions, the mutational profile was concordant in 1/7 (14.3 %). In all but two cases of SSL with dysplasia, MMR status was concordant between the two components of the serrated lesions. Our findings suggest that adenomatous dysplasia may develop in SSL as part of the serrated lesion, even if some SSL with dysplasia may actually be collision lesions. On the other hand, the polyps that are morphologically classifiable as mixed lesions composed of a HP and a conventional adenomatous component are more likely to be collision lesions.

FGFR2 rearrangements have been identified as a novel therapeutic target of biliary tract cancer (BTC). However, reliable prevalence estimates of this molecular alteration and its prognostic role have not been fully elucidated.A retrospective mono-institutional series of 286 patients affected by locally advanced or metastatic BTC (183 intrahepatic cholangiocarcinomas, 67 extrahepatic cholangiocarcinomas, 36 gallbladder carcinomas) was profiled by means of targeted DNA/RNA next-generation sequencing, immunohistochemistry and fluorescence in situ hybridisation for FGFR2/3, ERBB2, NTRK alterations, IDH1/2 and BRAF mutations and DNA mismatch repair complex proteins alterations/microsatellite instability.FGFR2 rearrangements, amplifications and point mutations were detected in 15 (5.2%), 1 and 3 cases, respectively. FGFR3 alterations were observed in 5 (1.7%) cases. IDH1/2 were mutated in 35/223 cases (15.7%). A total of 9/258 (3.5%) and 6/260 (2.3%) BTCs had ERBB2 and BRAF gene alterations, respectively. Two cases (2/242; 0.8%) had NTRK1 amplifications but no rearrangement was found. A deficit of mismatch repair protein expression was identified in 9/237 cases (3.8%). At multivariate analysis, age, ECOG performance status, number of metastatic sites, tumour stage, FGFR2/3 alterations and IDH1/2 mutations were prognostic factors of overall survival.These data provide a strong proof - challenged with a robust and detailed multivariate model - that FGFR2/3 aberrations (including FGFR2 rearrangements) and IDH1/2 mutations can be prognostic for better survival in patients with BTC . The recognition and the measurement of their prognostic impact could be of primary importance for the correct interpretation of currently available data and in the design of new therapeutic trials.

Carcinosarcomas are rare, highly aggressive neoplasms composed of a combination of carcinomatous and sarcomatous elements. These tumors represent a paradigmatic field for the study of intratumor heterogeneity. A series of 8 tubo-ovarian carcinosarcomas was characterized for the following: (i) immunohistochemical expression of MNF116, epithelial membrane antigen, vimentin, S100, chromogranin, synaptophysin, desmin, myogenin (MYF4), and p53; (ii) mutational profiling of KRAS, BRAF, PIK3CA, NRAS, TP53, and DICER1 genes. Heterologous differentiation was present in 6 of 8 tumors. Cytokeratin MNF116 and epithelial membrane antigen were positive in all the carcinomatous components and in 87.5% and 50.0% of the sarcomatous components, respectively. The sarcomatous components showed positive staining for vimentin in all cases. Two cases demonstrated positivity for neuroendocrine markers in their carcinomatous components. All rhabdomyosarcomas were positive for desmin and MYF-4. Chondrosarcomas were positive for S100. All but one tumor showed similar p53 immunoreactivity in both the carcinomatous and sarcomatous components, and one case showed cytoplasmic p53 expression. Three of 8 cases (37.5%) showed TP53 mutations, and, in 2 cases, the TP53 mutation was shared by both epithelial and mesenchymal components. DICER1 mutation was found in all components of one case. Mutations in KRAS, NRAS, BRAF, and PIK3CA genes were not found in the study cohort. Our results highlight the heterogeneity of ovarian carcinosarcomas at the phenotypic level. A common mutational signature was observed in both components in 3 of 4 informative tumors. More studies are required to dissect different levels of ovarian carcinosarcomas' heterogeneity in order to define the best therapeutic approaches to these aggressive neoplasms.

Background V600EBRAF mutated metastatic colorectal cancer (mCRC) is a subtype (10%) with overall poor prognosis, but the clinical experience suggests a great heterogeneity in survival. It is still unexplored the real distribution of traditional and innovative biomarkers among V600EBRAF mutated mCRC and which is their role in the improvement of clinical prediction of survival outcomes. Methods Data and tissue specimens from 155 V600EBRAF mutated mCRC patients treated at eight Italian Units of Oncology were collected. Specimens were analysed by means of immunohistochemistry profiling performed on tissue microarrays. Primary endpoint was overall survival (OS). Results CDX2 loss conferred worse OS (HR = 1.72, 95%CI 1.03–2.86, p = 0.036), as well as high CK7 expression (HR = 2.17, 95%CI 1.10–4.29, p = 0.026). According to Consensus Molecular Subtypes (CMS), CMS1 patients had better OS compared to CMS2-3/CMS4 (HR = 0.37, 95%CI 0.19–0.71, p = 0.003). Samples showing less TILs had worse OS (HR = 1.72, 95%CI 1.16–2.56, p = 0.007). Progression-free survival analyses led to similar results. At multivariate analysis, CK7 and CMS subgrouping retained their significant correlation with OS. Conclusion The present study provides new evidence on how several well-established biomarkers perform in a homogenousV600EBRAF mutated mCRC population, with important and independent information added to standard clinical prognosticators. These data could be useful to inform further translational research, for patients’ stratification in clinical trials and in routine clinical practice to better estimate patients’ prognosis.

The knowledge of the molecular landscape of ileal neuroendocrine tumors (NETs) is affected by the lack of systematic studies investigating intra-tumoral heterogeneity. In this study, intra-tumoral heterogeneity was investigated in 27 primary ileal G1-NETs and their matched nodal and liver metastases in order to assess the tumor grading, the expression status of two somatostatin receptor isoforms (i.e. SSTR2A and SSTR5) and mTOR signaling dysregulation (ph-mTOR, ph-p70S6K, ph-4EBP1, PTEN and miR-21). Among the 27 G1 primary tumors, 4 shifted to G2 in the matched liver metastasis. Although mTOR activation was pretty consistent between primary and secondary malignancies, mTOR effectors (ph-p70S6K and ph-4EBP1) were overexpressed in matched liver metastases, whereas PTEN expression profile changed in only two cases. MiR-21 was significantly up-regulated in the metastatic setting. Although SSTRs expression was present in most of the primary tumors and matched metastasis, we found SSTR5 expression to be significantly increased in liver metastases. Notably, SSTRs expression was heterogeneous within the same lesions in most of the lesions. Overall, despite primary and metastatic ileal NETs show a similar molecular landscape, tumor grading and mTOR signaling pathway may diverge in the metastatic setting, thus affecting prognosis and treatment.

2025 Background: Brain metastases (BM) from primary colorectal cancer (prCRC) are rare (1-3%); few is known about CRC BM predictive factors, prognosticators and molecular pathways. High rate of HER2 amplification ( HER2+) in CRC with BM was previously described, being HER2+ overall rare in CRC (

Purpose Non-neuroendocrine neoplasms of the appendix are a phenotypically heterogeneous group of lesions; a comprehensive molecular characterization of these tumors is still lacking. Methods A total of 52 samples taken from 49 patients was evaluated: 18 sessile serrated lesions (SSL; 3 with dysplasia), 2 high-grade tubular adenomas, 1 tubulo-villous adenoma,1 hyperplastic polyp, 18 low-grade appendiceal mucinous neoplasms (LAMN), 3 high-grade appendiceal mucinous neoplasms (HAMN) and 9 mucinous adenocarcinomas. Hotspot mutational profiling of the RNF43, SMAD4, KRAS, NRAS, BRAF and PIK3CA genes was performed. Expression of p53, MLH1, PMS2, MSH2, and MSH6 was evaluated by immunohistochemistry. Results KRAS was the most frequently mutated gene (53.9% of cases), followed by RNF43 (15.4%), and BRAF (13.5%). In particular: KRAS was mutated in 44.4% of adenocarcinomas, 66.7% of HAMNs, 61.1% of LAMNs, 53.3% of SSL without dysplasia and in 66.7% of SSL with dysplasia; RNF43 was mutated in 33.3% of adenocarcinomas, 66.7% of HAMNs, 11.1% of LAMNs and in 6.7% of SSL without dysplasia; BRAF was mutated in 11.1% of adenocarcinomas, 26.7% of SSL without dysplasia and in 5.6% of LAMNs. Only a case of high-grade tubular adenoma showed mismatch repair deficiency, while immunohistochemical expression of p53 was altered in 21.1% of cases. Conclusions The histological phenotypic similarities between appendicular mucinous lesions and serrated colon lesions do not reflect a similar genetic landscape. Mismatch repair deficiency is a rare event during appendiceal mucinous carcinogenesis.

PURPOSE More than 50% of patients with stage IV colorectal cancer (metastatic colorectal cancer [mCRC]) relapse postresection. The efficacy of postoperative systemic treatment is limited in this setting. Thus, these patients would greatly benefit from the use of a reliable prognostic biomarker, such as circulating tumor DNA (ctDNA) to identify minimal or molecular residual disease (MRD). PATIENTS AND METHODS We analyzed a cohort of 112 patients with mCRC who had undergone metastatic resection with curative intent as part of the PREDATOR clinical trial. The study evaluated the prognostic value of ctDNA, correlating MRD status postsurgery with clinical outcomes by using a personalized and tumor-informed ctDNA assay (bespoke multiple PCR, next-generation sequencing assay). Postresection, systemic therapy was given to 39.2% of the patients at the discretion of the treating physician. RESULTS Postsurgical, MRD positivity was observed in 54.4% (61 of 112) of patients, of which 96.7% (59 of 61) progressed at the time of data cutoff (hazard ratio [HR]: 5.8; 95% CI, 3.5 to 9.7; P < .001). MRD-positive status was also associated with an inferior overall survival: HR: 16.0; 95% CI, 3.9 to 68.0; P < .001. At the time of analyses, 96% (49 of 51) of patients were alive in the MRD-negative arm compared with 52.4% (32 of 61) in the MRD-positive arm. Patients who did not receive systemic therapy and were MRD-negative in the combined ctDNA analysis at two time points had an overall survival of 100%. In the multivariate analysis, ctDNA-based MRD status was the most significant prognostic factor associated with disease-free survival (HR: 5.78; 95% CI, 3.34 to 10.0; P < .001). CONCLUSION This study confirms that in mCRC undergoing resection of metastases, postoperative MRD analysis is a strong prognostic biomarker. It holds promises for being implemented in clinical decision making, informing clinical trial design, and further translational research.

Background Preclinical and clinical data indicate that p53 expression might modulate the activity of the epidermal growth factor receptor (EGFR), influencing response/resistance to anti-EGFR monoclonal antibodies. However, the association between p53 status and clinical outcome has not been clarified yet. Objective In our study, we evaluated the role of p53 expression in patients with RAS/BRAF wild-type metastatic colorectal cancer (mCRC) receiving irinotecan/cetuximab in an exploratory and a validation cohort. Patients and Methods p53 expression was analysed in patients with RAS/BRAF wild-type mCRC receiving second-line or third-line irinotecan/cetuximab. Survival distribution was assessed by the Kaplan–Meier method, while the log-rank test was used for survival comparison. Results Among 120 patients with RAS/BRAF wild-type mCRC included in our analysis, 52 (59%) and 19 (59%) patients showed p53 overexpression in the exploratory and validation cohort, respectively. In the exploratory cohort, low p53 expression was correlated with better median progression-free survival (hazard ratio 0.39; p < 0.0001), median overall survival (hazard ratio: 0.23; p < 0.0001) and response rate (p < 0.0001). These results were confirmed by data of the validation cohort where we observed better median progression-free survival (hazard ratio: 0.48; p = 0.0399), median overall survival (hazard ratio: 0.26; p = 0.0027) and response rate (p =0.0007) in patients with p53 normal expression mCRC. Conclusions In our study, p53 overexpression was associated with anti-EGFR treatment resistance in patients with RAS/BRAF WT mCRC, as confirmed in a validation cohort. Larger studies are needed to validate the role of p53 and investigate EGFR cross-talk in these patients.

Background: First-line decision making is the key to the successful care of mCRC patients and RAS/BRAF status is crucial to select the best targeted agent. In hub centers, a relevant proportion of patients referred from small volume centers may not have standard tissue-based (STB) molecular results available at the time of the first visit (T0). Liquid biopsy (LB) may help circumvent these hurdles. Methods: A monoinstitutional prospective head-to-head comparison of LB versus (vs.) STB testing was performed in a real-world setting. Selection criteria included: mCRC diagnosis with unknown RAS/BRAF status at T0, tumoral tissue archived in external centers, no previous treatment with anti-EGFR. At T0, patients underwent plasma sampling for LB testing and procedure for tissue recovery. RAS/BRAF genotyping was carried out by droplet digital PCR on circulating-tumoral (ct) DNA. The primary endpoint was the comparison of time to LB (T1) vs. STB (T2) results using the Mann–Whitney U test. Secondary endpoints were the concordance between LB and STB defined as overall percent agreement and the accuracy of LB in terms of specificity, sensitivity, positive and negative predictive value. We also performed an exploratory analysis on urinary (u) ctDNA. Results: A total of 33 mCRC patients were included. Mean T1 and T2 was 7 and 22 days (d), respectively (p &lt, 0.00001). T2 included a mean time for archival tissue recovery of 17 d. The overall percent agreement between LB and STB analysis was 83%. Compared to STB testing, LB specificity and sensitivity were 90% and 80%, respectively, with a positive predictive value of 94% and negative one of 69%. In detail, at STB and LB testing, RAS mutation was found in 45% and 42% of patients, respectively, BRAF mutation in 15%. LB results included one false positive and four false negative. False negative cases showed a significantly lower tumor burden at basal CT scan. Concordance between STB and uctDNA testing was 89%. Conclusions: Faster turnaround time, high concordance and accuracy are three key points supporting the adoption of LB in routinary mCRC care, in particular when decision on first-line therapy is urgent and tissue recovery from external centers may require a long time. Results should be interpreted with caution in LB wild-type cases with low tumor burden.

Cystic lesions of the pancreas may range from benign to precursors of pancreatic cancer. Simple mucinous cyst (SMC) is larger than 1 cm, has a gastric-type flat mucinous lining, and minimal atypia without ovarian-type stroma. We report a new case of pancreatic SMC, coupling a systematic review of the English literature mainly focused on their clinic-pathological features. We reviewed 103 cases of SMC in adults (73 women), averaging 57 (range, 26–70) years. The SMCs were located in the body-tail region of the pancreas in 60 (58%) cases, presenting as single cystic lesions in 94% of cases; 43% of patients were asymptomatic. A preoperative fine-needle aspiration of the cyst fluid detected amylase and carcinoembryonic antigen positivity in 71% and 76% of cases, respectively. Patients underwent surgery mostly for suspected malignancy; in 83% of cases, a standard pancreatic resection was performed. Mean SMC size was 4.9 (range, 1.5–12.0) cm. Mucins MUC5AC and MUC6 resulted positive in 77% and 81% of cases performed, respectively, whereas MUC2 was negative in all but one patient. The SMC from our institution was characterized by a KRAS somatic mutation. The diagnosis of SMC should be considered when a solitary pancreatic cyst larger than 1 cm is detected in asymptomatic patients. To establish a correct diagnosis, an extensive histologic/immunohistochemical analysis is essential. The presence of a KRAS mutation highlights that SMC may represent another potential pancreatic cancer precursor.

MicroRNAs (miRNAs) are small non-coding RNAs that play a pivotal role in many aspects of cell biology, including cancer development. Within esophageal cancer, miRNAs have been proved to be involved in all phases of carcinogenesis, from initiation to metastatic spread. Several miRNAs have been found to be dysregulated in esophageal premalignant lesions, namely Barrett’s esophagus, Barrett’s dysplasia, and squamous dysplasia. Furthermore, numerous studies have investigated the alteration in the expression levels of many oncomiRNAs and tumor suppressor miRNAs in esophageal squamous cell carcinoma and esophageal adenocarcinoma, thus proving how miRNAs are able modulate crucial regulatory pathways of cancer development. Considering these findings, miRNAs may have a role not only as a diagnostic and prognostic tool, but also as predictive biomarker of response to anti-cancer therapies and as potential therapeutic targets. This review aims to summarize several studies on the matter, focusing on the possible diagnostic–therapeutic implications.

We aimed to explore the activation of monoacylglycerol lipase (MAGL)/cyclooxygenase-2 (COX-2)/prostaglandin E

Low-grade neuroepithelial tumors (LGNT) show a broad histopathological spectrum and may be difficult to classify using current World Health Organization (WHO) criteria. A 57-year-old man came to medical attention because of headaches. The patient medical history was otherwise unremarkable. Magnetic resonance imaging (MRI) revealed a 2.5 cm lesion, partially cystic, with an increased signal on T2-weighted imaging, located in the right frontal lobe. The patient underwent right frontal craniotomy and the surgical specimen was entirely evaluated. Microscopic examination showed a tumor arranged predominantly in sheets and nests, with an infiltrative growth pattern and oligodendroglioma-like appearance. Tumor cells were round to oval with cytoplasmic clearing, hyperchromatic nuclei and inconspicuous nucleoli. Only one mitosis was identified. Necrosis was absent. Differential diagnostic considerations included oligodendroglioma, clear cell ependymoma, polymorphous low-grade neuroepithelial tumor of the young (PLNTY) and long-term epilepsy-associated tumor with clear cell morphology. Neoplastic cells showed positivity for glial fibrillary acidic protein (GFAP), oligodendrocyte transcription factor 2 (OLIG2), α-thalasemia X-linked mental retardation syndrome (ATRX) (retained nuclear expression) and CD34. Epithelial membrane antigen (EMA), neuronal nuclear antigen, microtubule-associated protein-2e, cyclo-oxygenase-2, chromogranin A and isocitrate dehydrogenase 1 (IDH1) (R132H) were negative. Ki-67 labeling index was 2-3%. Molecular analysis identified neither IDH1/IDH2 mutations nor 1p19q codeletion. Rapidly accelerated fibrosarcoma homolog B1 (BRAF) V600E mutation was also absent by both molecular and immunohistochemical testing. Polymerase chain reaction analysis revealed the presence of fibroblast growth factor receptor 3 (FGFR3)-transforming acidic coiled-coil (TACC) fusion. Taken together, the morphological, immunohistochemical and molecular findings supported the final diagnosis of PLNTY.

Background Intratumor heterogeneity (ITH) is described as the presence of various clones within one tumor, each with their own unique features in terms of morphology, inflammation, genetics or transcriptomics. Heterogeneity provides the fuel for drug resistance; therefore, an accurate assessment of tumor heterogeneity is essential for the development of effective therapies. The purpose of this study was to dissect morphologic and molecular ITH in colorectal adenocarcinoma. Materials and methods A series of 120 V600EBRAF-mutated (V600EBRAFmt) consecutive metastatic colorectal adenocarcinomas was assessed for morphologic heterogeneity. The two heterogeneous components of each specimen underwent a histopathological, immunohistochemical and molecular characterization to evaluate: histologic variant, grading, tumor-infiltrating lymphocytes (TILs), mismatch repair proteins' expression, KRAS/BRAF/NRAS mutations, microsatellite instability (MSI) status and consensus molecular subtype (CMS). Results Thirty-one out of 120 (25.8%) V600EBRAFmt primary colorectal adenocarcinomas presented a heterogeneous morphology. Among these, eight cases had adequate material for molecular profiling. Five out of the eight (62.5%) cases resulted instable at MSI testing. The majority (62.5%) of the samples showed a CMS4 phenotype based on gene expression profiling. Heterogeneity in CMS classification was observed in four out of eight cases. One out of eight cases presented significant heterogeneity in the number of TILs between the two components of the tumor. Conclusions Although the distribution of the immune infiltrate appears relatively conserved among heterogeneous areas of the same tumor, changes in gene expression profile and CMS occur in 50% of V600EBRAFmt adenocarcinoma cases in our small series and might contribute to variability in response to anticancer therapy and clinical outcomes. Assessment of morphological and molecular ITH is needed to improve colorectal cancer classification and to tailor anticancer treatments and should be included in the pathology report.

The main intent of secondary prevention strategies for Barrett's esophagus (BE) patients relies in the prompt identification of patients with dysplasia (or intra-epithelial neoplasia; IEN) and early-stage adenocarcinoma (Barrett's adenocarcinoma; BAc). Despite the adequate characterization of the molecular landscape characterizing Barrett's carcinogenesis, no tissue and/or circulating biomarker has been approved for clinical use. A series of 25 serum samples (12 BE, 5 HG-IEN and 8 BAc) were analyzed for comprehensive miRNA profiling and ten miRNAs were found to be significantly dysregulated. In particular seven were upregulated (i.e. miR-92a-3p, miR-151a-5p, miR-362-3p, miR-345-3p, miR-619-3p, miR-1260b, and miR-1276) and three downregulated (i.e. miR-381-3p, miR-502-3p, and miR-3615) in HG-IEN/BAc samples in comparison to non-dysplastic BE. All the identified miRNAs showed significant ROC curves in discriminating among groups with AUC values range of 0.75-0.83. Validation of the results were performed by droplet digital PCR in two out of three tested miRNAs. To understand the cellular source of circulating miR-92a-3p, we analyzed its expression in endoscopy biopsy samples by both qRT-PCR and ISH analyses. As observed in serum samples, miR-92a-3p was over-expressed in HG-IEN/BAc samples in comparison to naive esophageal squamous mucosa and BE and was mainly localized within the epithelial cells, supporting neoplastic cells as the main source of the circulating miRNA. Our data further demonstrated that circulating miRNAs are a promising mini-invasive diagnostic tool in the secondary follow-up and management of BE patients. Larger multi-Institutional studies should validate and investigate the most adequate miRNAs profile in discriminating BE patients in specific risk classes.

Background Analysis of deficiency in DNA mismatch repair (dMMR) is currently considered a standard molecular test in all patients with colorectal cancer (CRC) for its implications in screening, prognosis and prediction of benefit from immune checkpoint inhibitors. While the molecular heterogeneity of CRC has been extensively studied in recent years, specific data on dMMR status are lacking, and its clinical consequences are unknown. Case presentation We report the case of a metastatic CRC (mCRC) patient with immunohistochemical and molecular heterogeneity in dMMR/microsatellite instability status in the primary tumour. The patient was treated with nivolumab plus ipilimumab and achieved a deep and lasting response with clear clinical benefit. Whole-exome sequencing and RNA-seq data are reported to support the evidence for molecular heterogeneity. Re-biopsy at the time of progression ruled out the selection of MMR proficient clones as an escape mechanism. A large single-institution retrospective dataset was interrogated to further explore the real incidence of heterogeneity in its different presentations. Conclusions The present case supports the efficacy of immune checkpoint inhibition in mCRC with heterogeneity in MMR/microsatellite instability status. Clinical issues that may arise in these rare patients are discussed in detail.

Background Immunotherapy with immune checkpoint inhibitors (ICIs) is highly effective in microsatellite instability–high (MSI-H) metastatic colorectal cancer (mCRC); however, specific predictive biomarkers are lacking. Patients and Methods Data and samples from 85 patients with MSI-H mCRC treated with ICIs were gathered. Tumor infiltrating lymphocytes (TILs) and tumor mutational burden (TMB) were analyzed in an exploratory cohort of “super” responders and “clearly” refractory patients; TILs were then evaluated in the whole cohort of patients. Primary objectives were the correlation between the number of TILs and TMB and their role as biomarkers of ICI efficacy. Main endpoints included response rate (RR), progression-free survival (PFS), and overall survival (OS). Results In the exploratory cohort, an increasing number of TILs correlated to higher TMB (Pearson's test, p = .0429). In the whole cohort, median number of TILs was 3.6 in responders compared with 1.8 in nonresponders (Mann-Whitney test, p = .0448). RR was 70.6% in patients with high number of TILs (TILs-H) compared with 42.9% in patients with low number of TILs (odds ratio = 3.20, p = .0291). Survival outcomes differed significantly in favor of TILs-H (PFS: hazard ratio [HR] = 0.42, p = .0278; OS: HR = 0.41, p = .0463). Conclusion A significant correlation between higher TMB and increased number of TILs was shown. A significantly higher activity and better PFS and OS with ICI in MSI-H mCRC were reported in cases with high number of TILs, thus supporting further studies of TIL count as predictive biomarker of ICI efficacy. Implications for Practice Microsatellite instability is the result of mismatch repair protein deficiency, caused by germline mutations or somatic modifications in mismatch repair genes. In metastatic colorectal cancer (mCRC), immunotherapy (with immune checkpoint inhibitors [ICIs]) demonstrated remarkable clinical benefit in microsatellite instability–high (MSI-H) patients. ICI primary resistance has been observed in approximately 25% of patients with MSI-H mCRC, underlining the need for predictive biomarkers. In this study, tumor mutational burden (TMB) and tumor infiltrating lymphocyte (TIL) analyses were performed in an exploratory cohort of patients with MSI-H mCRC treated with ICIs, demonstrating a significant correlation between higher TMB and increased number of TILs. Results also demonstrated a significant correlation between high number of TILs and clinical responses and survival benefit in a large data set of patients with MSI-H mCRC treated with ICI. TMB and TILs could represent predictive biomarkers of ICI efficacy in MSI-H mCRC and should be incorporated in future trials testing checkpoint inhibitors in colorectal cancer.

Colorectal cancer (CRC) is a complex and molecularly heterogeneous disease representing one of the most frequent causes of cancer-related death worldwide. About 8–15% of CRCs harbor a mutation in BRAF gene, a proto-oncogene involved in cell proliferation, differentiation and survival through the MAPK signaling cascade. The acquisition of BRAF mutation is an early event in the “serrated” CRC carcinogenetic pathway and is associated with specific and aggressive clinico-pathological and molecular features. Despite that the presence of BRAF mutation is a well-recognized negative prognostic biomarker in metastatic CRC (mCRC), a great heterogeneity in survival outcome characterizes these patients, due to the complex, and still not completely fully elucidated, interactions between the clinical, genetic and epigenetic landscape of BRAF mutations. Because of the great aggressiveness of BRAF-mutated mCRCs, only 60% of patients can receive a second-line chemotherapy; so intensive combined and tailored first-line approach could be a potentially effective strategy, but to minimize the selective pressure of resistant clones and to reduce side effects, a better stratification of patients bearing BRAF mutations is needed.

Data from 117 patients withClass 3For the first time, different clinical and pathologic features and outcome data were reported according to the three

miR-224 has recently emerged as a driver oncomiR in sporadic colorectal carcinogenesis, but its pathogenetic role is still controversial. A large phenotypical and molecularly characterized series of preinvasive and invasive colorectal lesions was investigated for miR-224 expression by qRT-PCR and in situ hybridization. The caspase-3 and caspase-7 status was also assessed and correlated to miR-224 dysregulation. miR-224 was significantly upregulated during the adenoma-carcinoma sequence and in the context of inflammatory bowel disease dysplastic lesions, whereas its expression was significantly downregulated among BRAF-mutated tumors and in the presence of a DNA mismatch repair deficiency. miR-224 targets caspase-3 and caspase-7 in colorectal cancer, and this inverse relation was already evident from the earliest phases of transformation in intestinal mucosa. The miR-224/caspases axis may represent an interesting field of study for innovative biomarkers/therapeutics for BRAF-mutated/DNA mismatch repair-deficient tumors.

Colorectal cancer (CRC) is a heterogeneous group of diseases both from the morphological and molecular point of view. The sessile serrated adenoma/polyp (SSA/P) has been proposed as the precursor lesion of CRCs characterized by CpG island methylator phenotype (CIMP), DNA mismatch repair (MMR) system deficiency, and BRAF gene mutations. However, no study so far investigated the molecular landscape of "sessile serrated" adenoma to carcinoma transition in early CRCs. Six formalin-fixed paraffin-embedded CRCs developed within SSA/P were profiled for the immunohistochemical expression of MMR proteins (MLH1, MSH2, MSH6, PMS2, and Ep-CAM), p16, and β-catenin. DNA was extracted from the two components of each sample, after microdissection, and characterized for CIMP status and by applying a custom hotspot multigene mutational profiling of 164 hotspot regions of eleven CRC-associated genes (AKT1, APC, BRAF, CTNNB1, KIT, KRAS, NRAS, PDGFRA, PIK3CA, PTEN, and TP53). Five out of the six CRCs shared the same molecular profile (i.e. CIMP positive, MSI status, and BRAF mutation) with their SSA/P components. One out of five CRCs was also APC mutated, whereas another one showed an additional TP53 mutation. The remaining case was CIMP negative and MMR proficient in both the components, harbored a BRAF mutation in the SSA/P counterpart, whereas the CRC one was APC and TP53 mutated and showed p16 and β-catenin dysregulation. This study provides the molecular evidence that SSA/P, even without cytological dysplasia, is a precursor lesion of CRC and that conventional CRC might arise from mixed polyp.

Preoperative chemotherapy or combined radiotherapy and chemotherapy (CRT), followed by surgery, represents the standard approach for locally advanced esophageal, gastric, and rectal carcinomas. To adequately evaluate the effects of neoadjuvant CRT in the resection specimens, several histopathologic tumor regression grade (TRG) scoring systems have been introduced into clinical practice. The primary goal of these TRG systems relies on a correct prognostic stratification of patients in the attempt to help clinical decision-making and influence surgical strategies, postoperative adjuvant therapies, and surveillance intensity. However, most TRG systems suffer from poor reproducibility and low interobserver concordance rates. Many efforts have been made in the identification of alternative, robust, simple, and universally accepted TRG scoring systems, which would help in the comparison of different treatment strategies and in the standardization of multimodal therapies. The aim of this review is to analyze the most commonly used TRG systems in gastrointestinal cancers highlighting their pitfalls and usefulness, depending on the tumor type.

Purpose: BRAF mutations are grouped in activating RAS-independent signaling as monomers (class 1–V600E) or as dimers (class 2–codons 597/601), and RAS-dependent with impaired kinase activity (class 3–codons 594/596). Although clinical, pathologic, and molecular features of V600EBRAF-mutated metastatic colorectal cancer (mCRC) are well known, limited data are available from the two other classes. Experimental Design: Data from 117 patients with BRAF (92 class 1, 12 class 2, and 13 class 3)-mutated mCRC were collected. A total of 540 BRAF wt mCRCs were included as control. IHC profiling was performed to determine the consensus molecular subtypes (CMS), cytokeratin 7/20 profiles, tumor-infiltrating lymphocyte infiltration, and BM1/BM2 categorization. Overall survival (OS) and progression-free survival were evaluated by Kaplan–Meier and log-rank test. Results: Class 3 BRAF-mutated mCRC was more frequently left sided (P = 0.0028), pN0 (P = 0.0159), and without peritoneal metastases (P = 0.0176) compared with class 1, whereas class 2 cases were similar to class 1. Hazard ratio for OS, as compared with BRAF wt, was 2.38 [95% confidence interval (CI), 1.61–3.54] for class 1, 1.90 (95% CI, 0.85–4.26) for class 2, and 0.93 (95% CI, 0.51–1.69) for class 3 (P < 0.0001). Class 2 and 3 tumors were all assigned to CMS2-3. A higher median CD3/CD8-positive lymphocyte infiltration was observed in BRAF-mutated class 2 (P = 0.033) compared with class 3 cases. Conclusions: For the first time, different clinical and pathologic features and outcome data were reported according to the three BRAF mutation classes in mCRC. Specific targeted treatment strategies should be identified in the near future for such patients.

Background Claudin-18 (CLDN18) is a highly specific tight junction protein of the gastric mucosa. An isoform of CLDN18, the Claudin 18.2, has recently emerged as an innovative drug target for metastatic gastric cancer. Methods We investigated the immunohistochemical profile of CLDN18, p53, p16, E-cadherin, MSH2, MSH6, MLH1, PSM2, HER2, and PDL-1 in a large series of 523 primary gastric carcinomas (GCs; n = 408) and gastro-oesophageal carcinomas (GECs; n = 115) and 135 matched and synchronous nodal metastases. The status of HER2 and EBER by means of chromogenic in situ hybridisation (CISH) was also evaluated. Results High membranous CLDN18 expression was present in 150/510 (29.4%) primary cases and in 45/132 (34.1%) metastases. An abnormal expression (i.e. nuclear and/or cytoplasmic) was observed in 115 (22.5%) primary cases and in 33 (25.0%) metastases. A 38.8% of the cases showed significant CLDN18 intratumoural variability among the different tissue microarray cores obtained from the same tumour. Positive membrane CLDN18 expression was statistically associated with non-antral GCs (p = 0.016), Lauren diffuse type (p = 0.009), and with EBV-associated cancers (p

Background: No data is available on the molecular background of the extra-nodal extension (ENE) of lymph node metastasis (LN) in colorectal cancer (CRC). Methods: A series of 22 ENE-positive CRCs was considered and three samples per case were selected (the primary CRC, an ENE-negative and an ENE-positive metastatic LN). Samples (n=66) were analysed by immunohistochemistry for PD-L1, CD4, CD8, CD68 and CD80. Fifteen out of twenty-two cases were further profiled through a hotspot multigene mutational custom panel, including 164 hotspot regions of AKT1, APC, BRAF, CTNNB1, KIT, KRAS, NRAS, PDGFRA, PIK3CA, PTEN and TP53 genes. Results: A significantly higher percentage of CD4-, CD8- and CD68-positive cells was observed at the invasive front of both CRCs and in ENE in contrast with what observed at the core of both CRCs and their matched nodal metastases. ENE was also characterized by a significantly higher number of CD80-positive cells. No significant difference was observed in PD-L1 distribution among the different specimens. Fourteen out of 15 CRCs (93%) showed at least a driver mutation. The most frequently mutated gene was TP53 (n=8 tumors), followed by APC (n=6), BRAF (n=4), KRAS, NRAS and PIK3CA (n=2). In 11 out of 15 CRCs (73%) the mutational profiling of the primary tumor was consistent with what obtained from the two matched LNs. Conclusions: A heterogeneous intratumor immune-microenvironment has been observed in ENE-positive CRCs, which are characterized by an increased leukocytic infiltration at the ENE invasive front. © 2018 The Author(s).

Background ALK receptor tyrosine kinase gene (ALK) rearrangements have been described in spitzoid lesions with a plexiform growth pattern. Objective To investigate the prevalence of ALK alterations in a large series of spitzoid lesions. Methods ALK immunohistochemical and fluorescence in situ hybridization analyses of 78 spitzoid plexiform lesions including 41 Spitz nevi, 29 atypical Spitz tumors (ASTs), and 8 spitzoid melanomas. Results ALK immunohistochemical staining was observed in 14.6% of Spitz nevi (6 of 41) and 13.8% of ASTs (4 of 29); the spitzoid melanomas were ALK negative. Fluorescence in situ hybridization confirmed ALK translocation in 9 cases and amplification in 1 case. In 2 of the translocated cases it was possible to determine the fusion partner gene (ie, tropomyosin 3 gene [TPM3] or dynactin 1 gene [DCTN1]). Of the 4 cases of AST examined, 2 carried the B-Raf proto-oncogene, serine/threonine kinase gene (BRAF) V600E mutation. The 10 patients had a mean age of 18.7 years (range, 1-39) and a female predominance (female-to-male ratio, 7:3). Seven lesions arose on the extremities; the 2 lesions occurring in infants were located on the face. The lesions' mean diameter was 6.2 mm (range, 3-13), and their mean Breslow thickness was 1.83 mm (range, 0.6-3.6). The results of sentinel node biopsy were negative in 2 ASTs. Limitations BRAF status was tested in only 4 of 10 samples because of the limited amount of material. Conclusion ALK alterations characterize a significant subset of spitzoid lesions.