Primary acinar cell carcinoma of the liver.

We report a case of acinar cell carcinoma primary to the liver. The tumor was diagnosed in a 35-year-old woman complaining of abdominal pain and asthenia; serum alpha-fetoprotein (AFP) levels were increased at 6,000 IU/mL; imaging studies showed a hypervascular mass located in the left lobe of the liver. A left lobectomy was performed. The tumor had a heterogeneous appearance. In well-differentiated areas, tumor cells formed acinar structures, had a pyramidal shape and a highly eosinophilic, granular cytoplasm, PAS diastase resistant. In less-differentiated areas, tumor cells were endocrinelike. The immunohistochemical study showed that tumor cells expressed trypsin. Alpha-fetoprotein and alphal-antritrypsin were detected in about 30% of cells; HepPar1 was present in 15% of cells. Chromogranin A and synaptophysin were detected in rare cells. After surgery, serum AFP levels quickly returned to normal; no evidence of recurrence or metastasis was observed during follow-up. The final diagnosis, based on histological, immunohistochemical, and ultrastructural arguments, was extra-pancreatic acinar cell carcinoma, primary to the liver. This unusual lesion is likely to be the result of an abnormal differentiation pathway involving a transformed multipotential progenitor cell.