Serous microcystic adenoma (glycogen-rich cystadenoma) of the pancreas: study of 11 cases showing clinicopathological and immunohistochemical correlations.

Serous microcystic adenoma of the pancreas, also known as microcystic adenoma, glycogen-rich cystadenoma or serous cystadenoma, is an uncommon benign tumor. We have studied 11 cases involving eight women and three men. The average age at diagnosis was 61.7 years. Four tumors were discovered incidentally. Tumors varied from 1.2 to 20 cm in maximum diameter and all were multicystic. Within the pancreas, three were located in the pancreas head, one involved the head and body, one was located in the body, five were in the tail, and one occupied the whole pancreas. Central stellate scar was seen in five (45%) cases. Histologically, all tumors were composed of microglandular cysts lined by clear epithelial cells rich in glycogen, which were separated by fibrocollagenous stroma. The expression of keratin in clear epithelial cells resembled that in ductal and/or centroacinar cells, but not acinar cells. alpha-Smooth muscle actin (SMA)-positive myoepithelial cells and stromal amyloid deposits were not detected. Ultrastructurally, fibrocollagenous stroma was composed of alpha-SMA-positive myofibroblasts and endothelial cells embedded in thick collagen bundles. Regardless of female propensity, estrogen and progesterone receptors were not detected. Therefore, female predominance in this tumor remains to be elucidated.