α‑Fetoprotein‑positive hepatoid adenocarcinoma of the stomach and a new classification: A case report

α-Fetoprotein (AFP)-producing gastric carcinoma (AFPGC) is a rare subtype of gastric cancer (GC) with controversial classification methods. Hepatoid adenocarcinoma of the stomach (HAS) is another rare subtype of GC. Its definition intersects with that of AFPGC, but it is much rarer. The present report describes the case of an elderly patient with GC and AFPGC and HAS features in a serum test and pathology, respectively, and proposes a new classification of GC subtypes based on histological and AFP-producing features. A 75-year-old woman presented with a history of polydipsia and polyuria for over a decade and dizziness for 1 day. Serum AFP levels gradually elevated from 183.70 to 397.70 ng/ml in 1 month after the patient's first clinic visit. Subsequent pathological findings from endoscopic biopsy samples confirmed a hepatoid focus with positive immunohistochemical staining for AFP. The patient underwent a laparoscopic-assisted radical total gastrectomy and esophagojejunal Roux-en-Y anastomosis, and the serum AFP levels decreased to the normal range after the surgery. The present case indicates the diagnostic value of both the serum AFP level and pathological examinations in the diagnosis of AFPGC and HAS, and also highlights the contemporary circumstances of the vague classification based on different criteria for these two subtypes. Furthermore, the present report proposes a new classification considering both histological and AFP-producing features (using both serum biomarkers and immunohistochemistry tests) to cover all cases encompassed by AFPGC and HAS under all definition methods. This new method would give more precise diagnoses and add value to the subsequent treatment decision-making.