α‐Fetoprotein producing gastric carcinomas: A comparative study of three different subtypes

Nine cases of gastric carcinoma with excessive production of alpha-fetoprotein (AFP) were analyzed morphologically, histochemically and biochemically. Consequently, it was proposed that AFP-producing gastric carcinomas should be divided into three subtypes: (i) hepatoid type; (ii) yolk sac tumor-like type; and (iii) fetal gastrointestinal type. The data from the study suggested that the hepatoid type and the yolk sac tumor-like type are derived from liver cell metaplasia and yolk sac cell metaplasia of common poorly differentiated medullary adenocarcinoma, respectively. The fetal gastrointestinal type seemed to be a result of the imitation of fetal gastrointestinal epithelium by common tubular adenocarcinoma. The hepatoid type was also the most common in the file of AFP-producing gastric carcinoma. Unfortunately, most of the hepatoid types seemed to be highly malignant.