Case Report: Conversion therapy with chemotherapy, antiangiogenic therapy, and immunotherapy for locally advanced synchronous gastric hepatoid adenocarcinoma and poorly differentiated adenocarcinoma.

Hepatoid adenocarcinoma of the stomach (HAS) is a rare, aggressive gastric carcinoma that is frequently associated with elevated alpha-fetoprotein (AFP). We report a patient with resolved hepatitis B virus infection and two spatially distinct gastric lesions: poorly differentiated adenocarcinoma in the gastric body and HAS in the gastric angularis. The disease was initially considered unresectable. After multidisciplinary evaluation, the patient received oxaliplatin, S-1, sintilimab, and apatinib. Treatment produced radiological regression and AFP normalization, enabling total gastrectomy. Histopathology showed no viable carcinoma in either tumor bed or in 20 regional lymph nodes, confirming a pathological complete response. This case illustrates the potential role of individualized conversion therapy in selected patients with alpha-fetoprotein-producing gastric cancer. It does not establish the four-agent regimen as standard care. Interpretation is limited by the single-patient design, short follow-up, absence of lesion-specific sequencing and serial hepatitis B virus DNA data, and a nonstandardized maintenance strategy.