A case of mixed acinar-endocrine carcinoma of the pancreas discovered in an asymptomatic subject.

A 50-yr-old Japanese man was found to have a hypoechoic mass 3 cm in diameter in the pancreatic head on an ultrasonography (US) examination without symptoms. A computed tomography (CT) scan demonstrated a 3-cm solid mass in the pancreatic head, and it was more clearly delineated as a low-density area on enhanced CT. Angiography showed a tumorlike stain, 3 cm in size, in the pancreatic head. The preoperative diagnosis was "special type of pancreatic tumor such as acinar cell carcinoma or non-functioning islet cell tumor." The patient was treated by pylorus-preserving pancreatoduodenectomy. Histological, immunohistochemical, and electron-microscopic studies of the surgical specimen led to a definitive diagnosis of a mixed acinar-endocrine carcinoma. The patient is currently well, with no signs of tumor recurrence, 18 mo after the operation. Our search of the Japanese and English-language literature retrieved only 15 well-documented cases of mixed acinar-endocrine carcinoma. Imaging in the reported cases revealed features of either acinar cell carcinoma or islet cell tumor, or both, which can may be detected even in small tumors more easily than conventional invasive ductal carcinoma of the pancreas because the detectability of this rare tumor on US and CT seems to be good.