An unusual case of primary acinar cell carcinoma of the liver and its treatment.

Acinar cell carcinoma (ACC) is an epithelial neoplasm characterized by morphological features similar to acinar cells found in exocrine glands. Most cases of hepatic ACC reveal evidence of pancreatic exocrine enzyme production and are considered to be metastatic from the pancreas. However, a small number of hepatic ACC cases have been reported in which the tumor is believed to have originated in the liver rather than being a metastatic lesion. In this report we present a case of primary ACC of the liver. A 59-year-old female with no significant past medical history presented with the chief complaint of abdominal pain. A computed tomography (CT) scan of the abdomen showed innumerable mass lesions throughout the liver, initially concerning for metastatic disease. Histopathologic morphology was most consistent with that of ACC, possibly of pancreatic origin. However, the CA 19-9 level was not elevated and no pancreatic lesions were detected on the CT scan. Similar to a previously reported case, the diagnosis of primary ACC of the liver was made based on: acinar cells seen on histology, findings on immunohistochemical staining, radiographic images of liver masses, and the absence of extrahepatic lesions. Previous case reports of primary ACC have differing hypotheses regarding this rare finding. One hypothesis suggests an ectopic origin of acinar cells within the liver. An alternative hypothesis proposes that hepatic and pancreatic cells are ontogenetically derived from a common progenitor cell, which is thought to result in hepatic cells differentiating into acinar cells. The patient was treated with gemcitabine and paclitaxel every 2 weeks for 8 months and then transitioned to every 3 weeks for better tolerance. The patient's symptoms significantly improved within the first 6 weeks of treatment. At the time of the preparation of this report, it has been 17 months since initiation of therapy, and follow-up imaging continues to demonstrate a dramatic decrease in both size and number of hepatic nodules. ACC's are rare tumors that are usually found in glandular tissues. Primary ACC of the liver is extremely rare with only a few cases having been reported. This article adds to the limited literature available on primary hepatic ACC.