Clinical and Genomic Characterization of Pancreatic Ductal Adenocarcinoma with Signet-Ring/Poorly Cohesive Cells

Signet-ring cell (SRC)/poorly cohesive cell carcinoma is an aggressive variant of pancreatic ductal adenocarcinoma (PDAC). This study aimed to clarify its clinicopathologic and molecular profiles based on a multi-institutional cohort of 20 cases. The molecular profiles were investigated using DNA and RNA sequencing. The clinicopathologic parameters and molecular alterations were analyzed based on survival indices and using a validation/comparative cohort of 480 conventional PDAC patients. The primary findings were as follows: (1) clinicopathologic features: SRC carcinomas are highly aggressive neoplasms with poor prognosis, and the lungs are elective metastatic sites; (2) survival analysis: a higher SRC component was indicative of poorer prognosis. In particular, the most clinically significant threshold of SRC was 80%, showing statistically significant differences in both disease-specific and disease-free survival; (3) genomic profiles: SRC carcinomas are similar to conventional PDAC with the most common alterations affecting the classic PDAC drivers KRAS (70% of cases), TP53 (55%), SMAD4 (25%), and CDKN2A (20%). EGFR alterations, RET::CCDC6 fusion gene, and microsatellite instability (3 different cases, 1 alteration per case) represent novel targets for precision oncology. The occurrence of SMAD4 mutations was associated with poorer prognosis; (4) pancreatic SRC carcinomas are genetically different from gastric SRC carcinomas: CDH1, the classic driver gene of gastric SRC carcinoma, is not altered in pancreatic SRC carcinoma; (5) transcriptome analysis: the cases clustered into 2 groups, one classical/exocrine-like, and the other squamous-like; and (6) SRC carcinoma-derived organoids can be successfully generated, and their cultures preserve the histologic and molecular features of parental SRC carcinoma. Although pancreatic SRC carcinoma shares similarities with conventional PDAC regarding the most important genetic drivers, it also exhibits important differences. A personalized approach for patients with this tumor type should consider the clinical relevance of histologic determination of the SRC component and the presence of potentially actionable molecular targets.

Histo-molecular characterization of pancreatic cancer with microsatellite instability: intra-tumor heterogeneity, B2M inactivation, and the importance of metastatic sites

Pancreatic ductal adenocarcinoma (PDAC) with microsatellite instability (MSI)/defective mismatch repair (dMMR) is the only subtype of pancreatic cancer with potential response to immunotherapy. Here, we report the histo-molecular characterization of MSI/dMMR PDAC with immunohistochemistry, MSI-based PCR, and next-generation sequencing. Five paradigmatic cases have been identified. The main results include the first report in pancreatic cancer of MSI/dMMR intra-tumor heterogeneity, the presence of microsatellite-stable metastases from MSI/dMMR primary and recurrent B2M gene inactivation, which may confer resistance to immunotherapy. In addition to the classic PDAC drivers, ARID1A was the most common mutated gene in the cohort. Intra-tumor heterogeneity, B2M inactivation, and metastatic sites should be carefully considered in MSI/dMMR PDAC, which should also be investigated in routine diagnostic practice with specific molecular analysis. The chromatin remodeler ARID1A represents another potential driver gene in this context.

Molecular Analysis of an Intestinal Neuroendocrine/Non-neuroendocrine Neoplasm (MiNEN) Reveals MLH1 Methylation-driven Microsatellite Instability and a Monoclonal Origin: Diagnostic and Clinical Implications

Mixed neuroendocrine/non-neuroendocrine neoplasms (MiNEN) are rare mixed epithelial neoplasms in which a neuroendocrine component is combined with a non-neuroendocrine component. Here, we provide the clinical, pathologic, and molecular report of a 73-year-old-man presenting with an intestinal MiNEN. The lesion was composed of a well-differentiated G3 neuroendocrine tumor and a colloid adenocarcinoma. The molecular characterization was performed using a multigene next-generation sequencing panel. The neoplasm displayed microsatellite instability due to MLH1 promoter methylation. The extended molecular profile documented the same mutations affecting ARID1A, ASXL1, BLM, and RNF43 genes in both components, indicating a monoclonal origin of the tumor. Regarding component-specific gene mutations, BRCA2 was specifically altered in the neuroendocrine area. It may represent a new actionable target for precision oncology in MiNEN, but the lack of its alteration in the colloid component calls for further considerations on intratumor heterogeneity. The most important finding with potential immediate implications regards the presence of microsatellite instability: it indicates that this molecular alteration should become part of the diagnostic algorithm for these rare neoplasms.

Clinical presentation, genotype-phenotype correlations, and outcome of pancreatic neuroendocrine tumors in Von Hippel-Lindau syndrome

PURPOSE

Data regarding the clinical management and follow-up of pancreatic neuroendocrine tumors (PanNETs) associated with Von Hippel-Lindau (VHL) syndrome are limited. This study aimed to assess clinical presentation, genotype-phenotype correlations, treatment and prognosis of PanNETs in a series of VHL syndrome patients.

METHODS

Retrospective analysis of data of patients observed between 2005 and 2020.

RESULTS

Seventeen patients, including 12 probands and 5 relatives (mean age 30.8 ± 18.4; 7 males), were recruited. PanNETs were found in 13/17 patients (77.5%) at a median age of 37 years: 4/13 (30.7%) at the time of VHL diagnosis and 9 (69.3%) during follow up. Six (46.1%) PanNET patients underwent surgery, whereas seven were conservatively treated (mean tumor diameter: 40 ± 10.9 vs. 15 ± 5.3 mm respectively). Four patients (30.7%) had lymph node metastases and a mean tumor diameter significantly larger than the nonmetastatic PanNETs (44.2 ± 9.3 vs. 17.4 ± 7 mm, p = 0.00049, respectively). Five (83.3%) operated patients had stable disease after a median follow up of 3 years whereas one patient showed liver metastases. Six (85.7%) non-resected PanNETs were stable after a median follow-up of 2 years, whereas one patient developed a new small PanNET and a slight increase in diameter of a pre-existing PanNET. No correlation was found between the type of germline mutation and malignant behavior of PanNETs.

CONCLUSIONS

PanNETs are a common disease of the VHL syndrome and can be the presenting feature. Tumor size rather than genetic mutation is a prognostic factor of malignancy.

Genomic characterization of hepatoid tumors: context matters

Hepatoid tumors (HT) are rare neoplasms morphologically resembling hepatocellular carcinoma, which arise in several organs other than the liver. A comprehensive molecular profile of this group of neoplasms is still lacking. Genomic characterization of 19 HTs from different organs (three colon HTs, four esophagogastric HTs, four biliary HTs, six genitourinary HTs, two lung HTs) was performed using a multigene next-generation sequencing panel. NGS unraveled a composite molecular profile of HT. Their genetic alterations were clearly clustered by tumor site: (i) colorectal HT displayed microsatellite instability, high tumor mutational burden, mutations in ARID1A/B genes and NCOA4-RET gene fusion (2/3 cases); (ii) gastric HT had TP53 mutations (2/4); (iii) biliary HT displayed loss of CDKN2A (3/4) and loss of chromosome 18 (2/4); (iv) genital HT showed gain of chromosome 12 (3/6); (v) lung HT had STK11 somatic mutations (2/2). The only commonly mutated gene occurring in HT of different sites was TP53 (8/19 cases: colon 2, esophagogastric 2, biliary 2, genital 1, lungs 1). This study shows that most genetic alterations of HT were clustered by site, indicating that context matters. The novel potential targets for HT precision oncology are also clustered based on the anatomic origin. This study shed light on the biology of these rare cancers and may have important consequences for treatment decisions and clinical trial selection for HT patients.

Genetic Polymorphisms Involved in Mitochondrial Metabolism and Pancreatic Cancer Risk

BACKGROUND

The mitochondrial metabolism has been associated with pancreatic ductal adenocarcinoma (PDAC) risk. Recent evidence also suggests the involvement of the genetic variability of the mitochondrial function in several traits involved in PDAC etiology. However, a systematic investigation of the genetic variability of mitochondrial genome (mtSNP) and of all the nuclear genes involved in its functioning (n-mtSNPs) has never been reported.

METHODS

We conducted a two-phase association study of mtSNPs and n-mtSNPs to assess their effect on PDAC risk. We analyzed 35,297 n-mtSNPs and 101 mtSNPs in up to 55,870 individuals (12,884 PDAC cases and 42,986 controls). In addition, we also conducted a gene-based analysis on 1,588 genes involved in mitochondrial metabolism using Multi-marker Analysis of GenoMic Annotation (MAGMA) software.

RESULTS

In the discovery phase, we identified 49 n-mtSNPs and no mtSNPs associated with PDAC risk (P < 0.05). In the second phase, none of the findings were replicated. In the gene-level analysis, we observed that three genes (TERT, SUGCT, and SURF1) involved in the mitochondrial metabolism showed an association below the Bonferroni-corrected threshold of statistical significance (P = 0.05/1588 = 3.1 × 10^-5).

CONCLUSIONS

Even though the mitochondrial metabolism might be involved in PDAC etiology, our results, obtained in a study with one of the largest sample sizes to date, show that neither n-mtSNPs nor mtSNPs are associated with PDAC risk.

IMPACT

This large case-control study does not support a role of the genetic variability of the mitochondrial function in PDAC risk.

Association of Genetic Variants Affecting microRNAs and Pancreatic Cancer Risk

Genetic factors play an important role in the susceptibility to pancreatic cancer (PC). However, established loci explain a small proportion of genetic heritability for PC; therefore, more progress is needed to find the missing ones. We aimed at identifying single nucleotide polymorphisms (SNPs) affecting PC risk through effects on micro-RNA (miRNA) function. We searched in silico the genome for SNPs in miRNA seed sequences or 3 prime untranslated regions (3'UTRs) of miRNA target genes. Genome-wide association data of PC cases and controls from the Pancreatic Cancer Cohort (PanScan) Consortium and the Pancreatic Cancer Case-Control (PanC4) Consortium were re-analyzed for discovery, and genotyping data from two additional consortia (PanGenEU and PANDoRA) were used for replication, for a total of 14,062 cases and 11,261 controls. None of the SNPs reached genome-wide significance in the meta-analysis, but for three of them the associations were in the same direction in all the study populations and showed lower value of p in the meta-analyses than in the discovery phase. Specifically, rs7985480 was consistently associated with PC risk (OR = 1.12, 95% CI 1.07-1.17, p = 3.03 × 10-6 in the meta-analysis). This SNP is in linkage disequilibrium (LD) with rs2274048, which modulates binding of various miRNAs to the 3'UTR of UCHL3, a gene involved in PC progression. In conclusion, our results expand the knowledge of the genetic PC risk through miRNA-related SNPs and show the usefulness of functional prioritization to identify genetic polymorphisms associated with PC risk.

Tumor Mutational Burden as a Potential Biomarker for Immunotherapy in Pancreatic Cancer: Systematic Review and Still-Open Questions

Simple Summary

Tumor mutational burden (TMB) represents the number of mutations per megabase (muts/Mb) harbored by tumor cells in a given neoplasm, and can be determined with next-generation sequencing. High values are an indicator of potential response to immunotherapy. With this systematic review, we assessed its role in pancreatic ductal adenocarcinoma (PDAC). Our main findings can be summarized as: (i) high-TMB can be found in about 1% of PDAC; (ii) it is associated with mucinous/colloid and medullary histology; (iii) high-TMB PDAC frequently harbor other actionable alterations, with microsatellite instability as the most common; (iv) immunotherapy has shown promising results in high-TMB PDAC.

Abstract

Tumor mutational burden (TMB) is a numeric index that expresses the number of mutations per megabase (muts/Mb) harbored by tumor cells in a neoplasm. TMB can be determined using different approaches based on next-generation sequencing. In the case of high values, it indicates a potential response to immunotherapy. In this systematic review, we assessed the potential predictive role of high-TMB in pancreatic ductal adenocarcinoma (PDAC), as well as the histo-molecular features of high-TMB PDAC. High-TMB appeared as a rare but not-negligible molecular feature in PDAC, being present in about 1.1% of cases. This genetic condition was closely associated with mucinous/colloid and medullary histology (p < 0.01). PDAC with high-TMB frequently harbored other actionable alterations, with microsatellite instability/defective mismatch repair as the most common. Immunotherapy has shown promising results in high-TMB PDAC, but the sample size of high-TMB PDAC treated so far is quite small. This study highlights interesting peculiarities of PDAC harboring high-TMB and may represent a reliable starting point for the assessment of TMB in the clinical management of patients affected by pancreatic cancer.

Colorectal cancer with microsatellite instability: Right-sided location and signet ring cell histology are associated with nodal metastases, and extranodal extension influences disease-free survival

Colorectal cancer (CRC) with microsatellite instability (MSI) accounts for 15-18 % of all CRCs and represents the category with the best prognosis. This study aimed at determining any possible clinical/pathological features associated with a higher risk of nodal metastasization in MSI-CRC, and at defining any possible prognostic moderators in this setting. All surgically resected CRCs of the last 20 years (mono-institutional series) with a PCR-based diagnosis of MSI, with and without nodal metastasis, have been retrieved for histological review, which was performed following WHO guidelines. Furthermore, the most important prognostic moderators have been investigated with a survival analysis. The study of 33 cases of MSI-CRCs with nodal metastasis highlighted a high fidelity of histology maintenance between primary tumors and matched nodal metastases. At survival analysis, the strongest prognostic variable in MSI-CRCs with nodal metastasis was the extranodal extension (multivariate analysis, HR: 14.4, 95 %CI: 1.46-140.9, p = 0.022). Furthermore, through a comparison between nodal positive (33 cases) and nodal negative (71 cases) MSI-CRCs, right-sided location (p < 0.0001), pT4 stage (p = 0.0004) and signet-ring histology (p = 0.0089) emerged as parameters more commonly associated with nodal metastasization. These findings shed new light on the biology of MSI-CRC and can be of help for the prognostic stratification of MSI-CRC patients.

Solid Pseudopapillary Neoplasm of the Pancreas and Abdominal Desmoid Tumor in a Patient Carrying Two Different BRCA2 Germline Mutations: New Horizons from Tumor Molecular Profiling

This case report describes the history of a 41 year-old woman with a solid pseudopapillary neoplasm (SPN) of the pancreas and a metachronous abdominal desmoid tumor (DT) that occurred two years after the SPN surgical resection. At next-generation sequencing of 174 cancer-related genes, both neoplasms harbored a CTNNB1 somatic mutation which was different in each tumor. Moreover, two BRCA2 pathogenic mutations were found in both tumors, confirmed as germline by the sequencing of normal tissue. The BRCA2 mutations were c.631G>A, resulting in the amino-acid change p.V211I, and c.7008-2A>T, causing a splice acceptor site loss. However, as the two neoplasms showed neither loss of heterozygosity nor somatic mutation in the second BRCA2 allele, they cannot be considered as BRCA-dependent tumors. Nevertheless, this study highlights the important opportunities opened by extensive tumor molecular profiling. In this particular case, it permitted the detection of BRCA2-germline mutations, essential for addressing the necessary BRCA-related genetic counseling, surveillance, and screening for the patient and her family.

Comprehensive characterisation of pancreatic ductal adenocarcinoma with microsatellite instability: histology, molecular pathology and clinical implications

OBJECTIVE

Recently, tumours with microsatellite instability (MSI)/defective DNA mismatch repair (dMMR) have gained considerable interest due to the success of immunotherapy in this molecular setting. Here, we aim to clarify clinical-pathological and/or molecular features of this tumour subgroup through a systematic review coupled with a comparative analysis with existing databases, also providing indications for a correct approach to the clinical identification of MSI/dMMR pancreatic ductal adenocarcinoma (PDAC).

DESIGN

PubMed, SCOPUS and Embase were searched for studies reporting data on MSI/dMMR in PDAC up to 30 November 2019. Histological and molecular data of MSI/dMMR PDAC were compared with non-MSI/dMMR PDAC and with PDAC reference cohorts (including SEER database and The Cancer Genome Atlas Research Network - TCGA project).

RESULTS

Overall, 34 studies with 8323 patients with PDAC were included in the systematic review. MSI/dMMR demonstrated a very low prevalence in PDAC (around 1%-2%). Compared with conventional PDAC, MSI/dMMR PDAC resulted strongly associated with medullary and mucinous/colloid histology (p<0.01) and with a KRAS/TP53 wild-type molecular background (p<0.01), with more common JAK genes mutations. Data on survival are still unclear.

CONCLUSION

PDAC showing typical medullary or mucinous/colloid histology should be routinely examined for MSI/dMMR status using specific tests (immunohistochemistry, followed by MSI-PCR in cases with doubtful results). Next-generation sequencing (NGS) should be adopted either where there is limited tissue or as part of NGS tumour profiling in the context of precision oncology, acknowledging that conventional histology of PDAC may rarely harbour MSI/dMMR.

KRAS wild-type pancreatic ductal adenocarcinoma: molecular pathology and therapeutic opportunities

Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease, whose main molecular trait is the MAPK pathway activation due to KRAS mutation, which is present in 90% of cases.The genetic landscape of KRAS wild type PDAC can be divided into three categories. The first is represented by tumors with an activated MAPK pathway due to BRAF mutation that occur in up to 4% of cases. The second includes tumors with microsatellite instability (MSI) due to defective DNA mismatch repair (dMMR), which occurs in about 2% of cases, also featuring a high tumor mutational burden. The third category is represented by tumors with kinase fusion genes, which marks about 4% of cases. While therapeutic molecular targeting of KRAS is an unresolved challenge, KRAS-wild type PDACs have potential options for tailored treatments, including BRAF antagonists and MAPK inhibitors for the first group, immunotherapy with anti-PD-1/PD-L1 agents for the MSI/dMMR group, and kinase inhibitors for the third group.This calls for a complementation of the histological diagnosis of PDAC with a routine determination of KRAS followed by a comprehensive molecular profiling of KRAS-negative cases.

Cognitive and linguistic strategies in children with reading disabilities in an oral storytelling test

Three groups of children: 18 dyslexic children; 18 children with reading retardation: 18 normal children (mean age = 9 years), were given an oral storytelling test. The results point out a clear--cut differentiation between the three groups in their overall performance and the presence of atypical linguistic strategies in dyslexic children. The data are discussed in relation to linguistic difficulties in dyslexic children.