Gastric small-cell undifferentiated carcinoma with adeno and squamous cell carcinoma components.

A unique gastric tumor is reported. A large portion of the tumor consisted of a diffuse sheet of undifferentiated cells reminiscent of a small cell undifferentiated carcinoma. The tumor cells showed a few dense core granules and a poorly developed attachment apparatus by electron microscopy. In addition, small portions of the tumor showed adenocarcinoma and squamous cell carcinoma. Another noteworthy finding was that some of the metastatic hepatic nodules consisted of relatively monotonous polygonal cells with a distinct cord-like pattern showing argentaffinity and argyrophilia which were indicative of an atypical carcinoid. This case is a rare example of a gastric tumor with differentiation towards endocrine as well as adeno and squamous cell carcinoma.