Alpha‐fetoprotein–producing gastric carcinoma with enteroblastic differentiation

Background. Alpha‐fetoprotein (AFP) is a useful tumor marker for hepatoma and yolk sac tumor. Recently, elevations of serum AFP were reported in patients with other malignancies, especially gastric cancers. Two distinct tumor morphologies, hepatoid and clear cell, have been correlated with AFP production. Methods. Two patients with AFP‐producing gastric carcinoma were evaluated with immunohistochemical, ultrastructural, and biochemical studies. Results. In Patient 1, the primary and metastatic carcinomas consisted homogeneously of tubulopapillary carcinoma with clear cytoplasm. In Patient 2, the cancer was composed of three different areas: tubulopapillary carcinoma with clear cytoplasm, tumor cartilage, and so‐called hepatoid carcinoma. The morphologic characteristics of tubulopapillary carcinoma with clear cytoplasm were similar to those of the developing gut epithelium at the stage of 2–4 months' gestation. The elution patterns of the serum AFP on lectin‐affinity sepharose column study also suggested a correlation with fetal gut differentiation. Conclusions. AFP‐producing clear cell gastric carcinomas are differentiated into fetal intestine. One patient also had hepatocytic and cartilaginous differentiation, indicative of a blastomatous characteristic of the tumor. These tumors arose in association with intestinal metaplasia.