Malignant potential of aneuploid pancreatic endocrine tumours

Molecular subtyping in pancreatic neuroendocrine neoplasms: New insights into clinical, pathological unmet needs and challenges

Pancreatic neuroendocrine neoplasms (PanNENs) contain two primary subtypes with distinct molecular features and associated clinical outcomes: well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). PanNENs are a group of clinically heterogeneous tumors, whose diagnosis is based on tumor morphologic features and proliferation indices. However, these standards incompletely meet clinical needs by failing to adequately assess the likelihood of tumor recurrence and the potential for therapeutic response. We therefore focused on discussing molecular advances that facilitate the understanding of heterogeneity and exploration of reliable recurrence/treatment predictors. Taking advantage of high-throughput technologies, emerging methods of molecular subtyping in PanNETs include classifications based on co-existing multi-gene mutations, a large-scale loss of heterozygosity or copy number variation, and islet cell type-specific signatures. PanNEC molecular updates were discussed as well. This review aims to help the field classify PanNEN molecular subtypes, gain insights to aid in the solving of clinical, pathological unmet needs, and detect challenges and concerns of genetically-driven trials.

Review of the clinical, histological, and molecular aspects of pancreatic endocrine neoplasms

Pancreatic endocrine neoplasms (PENs) are rare tumors, and little is known about their genetic and chromosomal alterations. Elucidation of the molecular events involved in PEN carcinogenesis has been hindered by the fact that PENs have been considered a single disease entity. The emergence of novel molecular characterization strategies has, however, made it apparent that these lesions exhibit diverse molecular fingerprints, which will facilitate the precise delineation of PEN prognosis, histopathology, and carcinogenesis.

Malignancy-associated allelic losses on the X-chromosome in foregut but not in midgut endocrine tumours

Information on genetic changes involved in the progression of gastroenteropancreatic (GEP) endocrine tumours is scanty. On the other hand, the identification of molecular markers of malignancy could be crucial for the prognostic evaluation of these neoplasms, which is hardly predictable on the basis of conventional histological criteria. An association of X-chromosome deletions with malignancy has already been found in gastric endocrine tumours. To investigate this further, a comparative loss of heterozygosity (LOH) analysis was performed on 17 pancreatic endocrine tumours (PETs) and 17 intestinal (ten ileal, six appendiceal, and one rectal) carcinoids from female patients. The relationship of X-chromosome LOH with the ploidy status of the neoplasms was also investigated. LOH was found in six of eight malignant PETs (60% of the informative markers), but was infrequent in the nine benign ones (4.5%). In contrast, although retention of heterozygosity was consistently observed in benign midgut tumours, LOH was infrequent in malignant carcinoids (15%). No correlation was found between LOH and the ploidy status. These results indicate an association between X-chromosome LOH and malignancy in foregut endocrine tumours. The lack of such an association in midgut carcinoids suggests that different molecular mechanisms are involved in the progression of these two categories of endocrine neoplasms, which are otherwise considered to be closely related. These findings emphasize the need for further molecular studies on GEP endocrine tumours, carefully subdivided according to their anatomical site of origin.

Lack of p53 immunoreactivity in pancreatic endocrine tumors

Abnormal expression of the p53 tumor suppressor gene has been implicated in many human epithelial tumors. However recent evidence has revealed the absence of p53 gene abnormalities or overexpression in some human endocrine cancers. This study examines the immunohistological expression of the p53 gene product using the monoclonal antibody DO-7, an antibody directed against both wild and mutant forms of p53 protein, and a streptavidin-biotin-peroxidase method, in pancreatic endocrine tumors (n = 16). None of the cases of pancreatic endocrine tumors showed evidence of p53 immunostaining. This finding is in contrast to that in pancreatic adenocarcinomas in which increased p53 immunoreactivity has been previously observed. These observations suggest that the p53 gene may not be important in the development of endocrine tumors of the pancreas.

DNA ploidy and PCNA index in pancreatic lesions producing hyperinsulinemic hypoglycemia

DNA nuclear content and PCNA index (proportion of PCNA reactive cells) have been studied by flow cytometry in eight pancreatic lesions producing hyperinsulinemic hypoglycemia to assess DNA ploidy and tumoral growth fraction. Adult nesidioblastosis had a diploid DNA index, two adenomas were near diploid, and four of the adenomas and the carcinoma were aneuploid. The median value of PCNA index (6.056% +/- 6.76) was significantly correlated (P < 0.05) with the mean tumor diameter (2.43 cm +/- 1.96). Tumors with a PCNA index < 6.056% showed a diameter less than the mean tumoral diameter and a benign clinical course. Tumors with PCNA index > 6.056% generally displayed a diameter bigger than the mean tumoral diameter, being associated with lymph node metastases in one case. The authors conclude that nuclear DNA and PCNA index cytometric studies are useful parameters to assess the biological behavior of pancreatic lesions producing hyperinsulinemic hypoglycemia.

Aneuploid islet cell tumor with late metastasis

An unusual case of insulin producing islet cell tumor is reported which recurred after a 16 yr interval. In most instances malignancy of islet cell tumors is impossible to assess morphologically or functionally but depends on the recognition of metastases. Nuclear DNA analysis provides significant prognostic and biological information in a number of solid human tumors. Retrospective computerized nuclear image analysis of the primary tumor in the present case showed an aneuploid DNA profile similar to that seen in the metastasis. It appears that ploidy studies may be useful in predicting malignant potential of islet cell tumors.