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We examined a 70-year-old woman in whom a pancreatic endocrine tumor with partial acinar cell differentiation had been diagnosed. She had neither endocrine nor exocrine symptoms. The tumor was located in the pancreatic tail and measured 12.5×9.5×8 cm. It had a capsule, was composed of multiple adhesion nodules, and was elastically soft, medullary, and yellowish white. The neoplastic cells had large, irregular, oval nuclei; prominent eosinophilic nucleoli; and abundant eosinophilic cytoplasm with many fine granules. The cells had proliferated in islet-like solid medullary, trabecular, acinar, and papillary patterns. Most neoplastic cells were strongly positive for synaptophysin. 10 to 25% of the neoplastic cells were positive for α1-antitrypsin. Neuroendocrine and zymogen granules were simultaneously observed in the cytoplasm of the same neoplastic cells at the ultrastructural level. The tumor may be considered an amphicrine tumor. [ABSTRACT FROM AUTHOR]

Mucinous cystic neoplasms (MCN) of the pancreas are mucin-producing cystic tumors with an ovarian-like stroma (OLS). In the present study MCN were obtained from 27 patients. These MCN were derived from 22 pancreas, three livers, spleen, and mesentery. MCN in various organs have common clinicopathological profiles, being unilocular or multilocular cystic tumors, with a fibrous capsule and lined by mucin-secreting epithelium associated with an underlying subepithelial OLS. The OLS showed strong positivity for α-smooth muscle actin (α-SMA) and vimentin and weak, focal positivity for desmin. Both estrogen receptors and progesterone receptors were expressed in the nuclei of OLS cells. In addition, 20 ovarian MCN and 13 normal ovaries were studied with particular attention to the stroma. The stroma of ovarian MCN was strongly immunopositive for α-SMA and vimentin and focally positive for desmin, whereas normal ovarian stroma was immunonegative for both α-SMA and desmin. The OLS of MCN mentioned here was similar to the septa of ovarian MCN but not to ovarian stroma. In conclusion, MCN in various organs should be lumped together as ‘extraovarian’ MCN. The OLS was identified on the basis of myofibroblastic proliferation both in response to neoplastic development and dependent on hormones. [ABSTRACT FROM AUTHOR]