A Clinical Guidance for the Management of Patients With Hepatoid Adenocarcinoma and A Case Series

Hepatoid adenocarcinoma (HAC) is a rare extrahepatic tumor of non-germ cell origin that morphologically resembles hepatocellular carcinoma (HCC). HAC has a propensity to metastasize to the liver and therefore may be mistaken for HCC. There is a lack of standardized treatment protocols, and further studies are needed to evaluate the benefit of targeted therapy and immunotherapy. Recent studies have reported that tumor protein 53 (TP53) gene mutations are associated with increased expression of programmed cell death ligand-1 (PD-L1), which may be a predictor of response to PD-L1 targeted checkpoint inhibitors. This review provides a clinical guidance for the management of patients with HAC by summarizing the salient clinical features, risk factors, diagnostic criteria, differential diagnosis, new therapeutic approaches, and prognosis of this rare tumor. Furthermore, we reviewed the Mayo Clinic experience to describe the clinical characteristics of 15 patients diagnosed with HAC. HAC is usually diagnosed at an advanced stage with distant metastases. In patients diagnosed with liver lesions that have similar radiologic and histologic features to HCC, particularly in the absence of underlying chronic liver disease, further evaluation should be performed to rule out HAC. Communication between medical subspecialties is important to avoid misdiagnosis and prevent further disease progression. In our patient cohort TP53 was the most frequently mutated gene (5 out of 8, 62.5%) and PD-L1 expression showed a positive score in 3 out of 6 patients (50%). However, only a few patients received immunotherapy (6 out of 14, 42.9%) suggesting that the numbers are too small to draw a conclusion about its efficacy in treating HAC.