A rare neuroendocrine tumor of pancreas characterized by a well-differentiated epithelial pancreatic neuroendocrine neoplasm measuring at least 0.5 cm, without distinct hormonal syndrome. Tumors less than 0.5 cm are called microadenomas. Microadenomatosis is the multifocal occurrence of microadenomas. Histopathologic examination shows an organoid growth pattern and expression of synaptophysin and chromogranin A on immunohistochemistry. Tumors are often discovered incidentally, or patients may present with symptoms related to local or metastatic tumor spread. Microadenomas are considered benign, while larger tumors may behave in a malignant manner with extrapancreatic spread, metastasis, or recurrence. [from
SNOMEDCT_US]