Pancreatoblastoma in Japan, with differential diagnosis from papillary cystic tumor (ductuloacinar adenoma) of the pancreas.

Twelve cases of pancreatoblastoma, 7 males and 5 females, were 5 years of age in average and showed an organoid structure consisting of acinar differentiation with squamoid corpuscles. Seven cases died, but 5 lived after surgery. On the contrary, 17 cases of papillary cystic tumor, ductuloacinar adenoma of the pancreas, one male and 16 females, were 21 years of age in average and disclosed a monomorphous pseudopapillary pattern of ductuloacinar type of tumor cells with some degenerative and granulomatous changes. All of the cases had suffered no recurrence after resection. Immunohistochemically, strong positivity for alpha 1-antitrypsin may be associated with the autodigestive process and limited growth of this tumor. Electron microscopically, both tumors showed centroacinar and acinar types of tumor cells. Both tumor cells frequently contained well-developed RER, zymogen-like granules, and annulate lamellae. The ductular or acinar lumina were clear in pancreatoblastoma, but not in ductuloacinar adenoma due to degeneration. Though both tumors disclosed contiguous histogenesis, pancreatoblastoma should be differentiated from ductuloacinar adenoma, based upon the young age, almost equal sex ratio, unfavorable prognosis, high serum AFP level in three measured cases, an organoid structure containing frequent mitotic figures, and the invasive growing margin.