Undifferentiated carcinoma of the colon containing exocrine, neuroendocrine and squamous cells.

The light microscopic, electron microscopic and histochemical features of a highly malignant colonic tumor resected from a 39 year old man are presented. The tumor was composed predominantly of undifferentiated cells with focally admixed neuroendocrine, exocrine and squamous cells, occasionally arranged in an organoid manner. Histochemically the tumor contained argyrophilic cells as well as cells that reacted positively with the antibodies to alpha-1-antitrypsin, alpha-1-antichymotrypsin, carcinoembryonic antigen and lysozyme. The term "stem cell carcinoma of the intestine" is proposed for this highly malignant tumor composed of undifferentiated cells exhibiting only focally their multidirectional developmental capacity.