Merged hepatopulmonary features in hepatoid adenocarcinoma of the lung: a systematic review

This study aimed to provide diagnostic clues for patients with elevated serum alpha-fetoprotein (AFP) in the absence of liver tumors and rectify some previously confused concepts about hepatoid carcinoma of the lung through a systematic review on hepatoid adenocarcinoma of the lung (HAL). A thorough search for original articles on HAL published prior to November 2020 was performed using the PubMed, EBSCOhost, Embase, WanFang Data, and China National Knowledge Infrastructure (CNKI) databases. Ninety-four patients from 88 studies met the eligibility criteria. HAL was rare and mainly occurred among male Asian smokers in their 60 s, presenting with cough, hemoptysis, chest pain, dyspnea and/or weight loss, as well as elevated serum AFP with a mass usually in the right upper lung lobe but no liver masses. Hepatoid differentiation regions, acinar or papillary structures in tumor tissues, and positive immunohistochemical expression of AFP, HepPar-1, and CK8/18 were crucial indicators for the diagnosis of HAL. Surgery-based strategies were recommended for stage I-III patients, while stage IV patients were mainly treated with chemotherapy-based strategy. The 1-, 3-, and 5-year overall survival rates were 40%, 35%, and 19%, respectively. The 1-year relapse-free survival rate was 58%. The postoperative monitoring of AFP contributed to the early detection of tumor recurrence, with a positive rate of 71.43%. In conclusion, patients with elevated serum AFP levels without any detectable hepatic lesions should be evaluated for the possibility of HAL.