[Immunocytohistochemical studies of AFP producing gastric cancer--cytomorphology and characteristics of AFP positive cells].

In 24 cases (5.5%) out of 438 cases of gastric cancer showing serum AFP over 20 ng/ml, 14 cases (3.2%) showed AFP positive reaction in cancer cells by immunostaining. AFP localization in cancer cells classified into marginal type, granular type, diffuse type and inclusion type. Mixed combination of these types increased in high serum AFP level. Cytomorphology of AFP positive cells was classified to clear cell type, hepatoid cell type and round cell type. Clear cell type showed endodermal sinus like pattern in histomorphology. Clear cell type and hepatoid cell type were mixed, and transient. These types showed eosinophilic hyaline like globules, poor mucin production, and rich glycogen in cytoplasm. By immunohistochemistry showed positive rate in HCG:21.4%, PLAL:50. 0%, SP1:50.0%, CK:14.3% and alpha 1-AT:92.9%, and recognized reaction of germ cell tumor (endodermal sinus tumor) marker. We thought AFP producing gastric cancer suggested differentiation to germ cell tumor (endodermal sinus tumor). The AFP-positively stained cases were found in a high age group with advanced cancer located pylorus to corpus, medullary growth pattern, and high rate in liver metastases.