Fibrolamellar hepatocellular carcinoma (fHCC) is a rare primary liver neoplasm that makes 0.6% to 8.6% of all hepatocellular carcinomas (HCC)1. Patients with fHCC have a particular predilection for Hyperammonemia encephalopathy2. If HAE in fHCC is found to be in association with urea cycle defects, administration of sodium phenylbutyrate is one of several treatment options available to reduce plasma ammonia levels4.