Hepatoid adenocarcinoma of the lung: Review of a rare form of lung cancer.

RATIONALE: Hepatoid adenocarcinoma (HAC) is a rare malignant lung tumor that histologically resembles typical hepatocellular carcinoma (HCC) when it is metastatic to the lung. To date, this clinical entity has not been highlighted in the pulmonary literature.

OBJECTIVE: We present a review of all known cases of HAC, including the relevant clinical and histopathological features important for pulmonologists.

MEASUREMENTS AND MAIN RESULTS: The purpose of this report is to present a new case of HAC, with typical clinical and histologic features of this malignancy, and to summarize findings of previously reported cases. A systematic literature search of the electronic database PUBMED was conducted to identify all cases of hepatoid adenocarcinoma reported in the English literature, between January 1980 and June 2015. HAC and HCC can be distinguished by immunohistochemical staining. HAC usually presents as a large bulky solitary mass in the upper lobe; there is an exceedingly high prevalence in males and most patients with this tumor are smokers. Serum alpha-fetoprotein (AFP) in very high levels has been a distinguishing feature of this tumor. Nodal and distant metastases are common at initial presentation and, as a result, the prognosis is very poor. Resection and long-term survival, however, have been reported.

CONCLUSION: Hepatoid adenocarcinoma, first described as a gastric tumor, has also been described in the lung. It morphologically resembles and must be distinguished from metastatic HCC of the lung. While most tumors produce AFP, the case we present demonstrates that this should not be a criterion for diagnosis.