Pancreatic-type acinar cell carcinoma of the liver: a clinicopathologic study of four patients.

Acinar cell carcinoma of pancreatic type rarely occurs at extra-pancreatic sites. We report four primary liver tumors with features of pancreatic acinar cell carcinoma. The patients were two males and two females with a mean age of 65 years (range, 49-72 years). They had upper abdominal pain, weight loss and/or an incidentally discovered liver mass. None had evidence of a primary pancreatic tumor. Grossly, the tumors were large (mean size, 12 cm), well circumscribed and showed a lobulated cut surface. Histologically, they showed a predominantly microacinar pattern, with occasional trabecular, solid and microcystic areas. Cellular atypia and mitotic activity varied within the same tumor and from tumor to tumor. Immunohistochemically, the tumor cells were positive for cytokeratin 18 and at least one acinar cell marker (ie, trypsin, amylase or lipase), but were negative for cytokeratins 7, 19 and 20, HepPar-1, AFP, CD10, carcinoembryonic antigen, CD56, Islet-1 and CDX2. Two tumors stained focally for synaptophysin and chromogranin A. Adjacent liver parenchyma displayed no evidence of cirrhosis. During a mean follow-up of 22 months (range, 3-38 months) no metastases occurred, but one patient developed local recurrence. Our study demonstrates that acinar cell carcinoma of pancreatic type may also originate from the liver and can be readily distinguished from other primary liver neoplasms by its distinct histological and immunohistochemical features. Because our cases were observed within a rather short period, it is likely that this tumor type is so far underrecognized and has been mistaken as a variant of hepatocellular carcinoma, cholangiocarcinoma or any other liver tumor.