Adenosquamous carcinoma of the stomach: histological, histochemical and ultrastructural observations.

The histochemical and ultrastructural features of an adenosquamous carcinoma of the stomach have been studied. Both the adenomatous and the squamous component of the tumour showed malignant characteristics. Elements which were considered as undifferentiated cells on light microscopy showed ultrastructural features of poorly differentiated squamous cells. No intermediate cells, sharing squamous and glandular aspects, were found by electron microscopical examination. The adenomatous component exhibited histochemical and ultrastructural features of the intestinal type of gastric carcinoma and the mucosa surrounding the tumour showed a colonic type of intestinal metaplasia. A possible histogenesis from a totipotential undifferentiated cell is considered.