A Case of the Gastric Carcinoma with Extragastric Growth and Differentiation to Yolk Sac Tumor

A 43-year-old woman presented with anemia and a large tumor in the lower abdomen, and the tumor was diagnosed as gastric carcinoma (type 2) with extra-gastric growth by CT, MRI, and UGI endoscopy. The serum AFP level was extremely high (42, 735ng/ml). Distal gastrectomy and resection of the transverse colon was performed. The large tumor (14×12×12cm) arose from the antrum of the stomach, and it involved the mesocolon of the transverse colon. The histological diagnosis showed that the tumor consisted of two components. One was a moderately differentiated adenocarcinoma of a Type 2 cancer, and the other was a yolk sac tumor of an extragastric growth component. Immunohistochemically, AFP was positive in almost all of the yolk sac tumor cells and in a few of the adenocarcinoma cells. This finding suggests that the yolk sac tumor arose from the component of the adenocarcinoma that was AFP-positive.