PROGNOSTIC CRITERIA IN NONFUNCTIONING PANCREATIC ENDOCRINE TUMORS

To identify prognostic subgroups among nonfunctioning (nonsyndromic) p ancreatic endocrine tumours, a series of 61 rumours were analysed syst ematically for macroscopic, histopathological and immunohistochemical variables potentially predictive of malignancy. High-grade nuclear aty pia, elevated mitotic rate and multifocal necrosis allowed us to separ ate 5 poorly differentiated carcinomas from 56 well differentiated tum ours. Among the latter, 29 well-differentiated carcinomas showing gros s local invasion or metastases were identified. Vascular or perineural microinvasion, Ki67 proliferative index >2%, mitotic rate greater tha n or equal to 2, size greater than or equal to 4 cm, capsular penetrat ion, nuclear atypia, lack of progesterone receptors and presence of ca lcitonin were among the variables correlated with malignancy. The firs t two were the most sensitive and specific. Their presence or absence was used in the 27 rumours lacking evidence of malignancy at the time of surgery to separate 11 cases with increased risk of malignancy (in 2 of which metastases developed during follow-up) from 16 cases with l imited risk. The resulting four prognostic groups of nonfunctioning pa ncreatic endocrine rumours (limited- and increased-risk rumours, well- differentiated carcinomas and poorly differentiated carcinomas) showed distinct survival curves, which were significantly affected by vascul ar microinvasion, Ki67 proliferative index and metastases.