[Characteristics of gastric hepatoid adenocarcinoma: a clinicopathological and molecular analysis]

Objective: To investigate the clinical, pathological, and molecular biological characteristics of gastric hepatoid adenocarcinoma (HAS) in order to provide reference for clinical treatment. Methods: Thirty-two patients diagnosed with hepatoid adenocarcinoma after radical gastrectomy for gastric cancer at Shanxi Cancer Hospital were included from January 2019 to December 2021. Immunohistochemistry, in situ hybridization, and next-generation sequencing (NGS) methods were used to analyze immune markers and molecular characteristics in the pathological tissues from 32 patients with HAS. Cox regression analysis and Kaplan-Meier method were used to analyze the prognostic factors of overall survival and disease-free survival. Results: Among the 32 patients with HAS, 26 were male, 6 were female; aged 28-77 years, with an median age 62.0 (53.8, 67.2) years. Fifteen cases of HAS were located in the cardia, 10 cases in the antrum, and 7 cases in the body of the stomach. The maximum diameter of the mass was 3-10 cm, and mainly ulcerative in gross. The immunohistochemistry and in situ hybridization results showed that the positive rates of AFP, SALLA4, and Glypican-3 were 68.8% (22/32), 68.8% (22/32), 78.1% (25/32), respectively; Seven patients had microsatellite status of dMMR. Two cases of HER2 gene amplification and 2 cases of EB virus positivity. The NGS results showed that HAS was often accompanied by multiple gene mutations, with 23 cases having ≥ 2 gene mutations and 6 cases having ≥10 gene mutations. The TP53 gene had the highest mutation frequency; 4 cases had genetic structural variations; 28 cases had copy number variation. In addition, there were 7 cases of MSI-H and 9 cases of TMB-H. Follow-up results showed that 12 cases died, 9 cases developed metastasis, and the shortest survival time was 5 months. Conclusions: Gastric HAS is a type of tumor with high invasiveness and poor prognosis. The combined detection of AFP, SALLA4 and Glypican-3 can improve the diagnostic rate of tumors. dMMR/MSI-H and TMB-H patients in HAS are significantly higher than those in ordinary gastric cancer, and the high frequency mutation genes in HAS are often accompanied by multiple potential therapeutic targets. Immunotherapy combined with chemotherapy and targeted therapy are expected to become the treatment direction of HAS.