Pathological assessment of pancreatic endocrine tumors for metastatic potential and clinical prognosis

The prognostic significance of several pathological factors (tumor size, mitotic index, Ki-67 labeling index, and vascular invasion) and expression of exocrine markers (CA19-9, CEA, AFP, and trypsin) in pancreatic endocrine tumors was studied. A total of 20 specimens of metastasizing (n=10) and non-metastasizing (n=10) tumors were subjected to histological and immunohistochemical examination. The metastasizing tumors showed significantly larger size, higher Ki-67 labeling index, increased number of mitotic cells, and more frequent vascular invasion in comparison with the non-metastasizing tumors. It was difficult to determine the effect of individual factors on clinical outcome because of slow disease progression in almost all cases. Numerous mitotic cells and widespread necrosis, however, were thought to indicate a poor prognosis, and tumors with these characteristics were regarded as high-grade malignant endocrine carcinomas. In one case, one-third of the tumor tissue comprised trypsin-positive cells, the outcome was comparatively poor, and the behavior of the tumor resembled that of mixed acinar-endocrine carcinoma. A simple multifactorial approach may be effective for the identification of tumors at increased risk of metastasis, but it remains difficult to determine clinical prognosis. It is essential to at least distinguish high-grade endocrine carcinomas from the more common endocrine tumors.