Distinctive intestinal mast cell neoplasms of domestic cats.

By use of histologic, histochemical, and ultrastructural techniques a group of distinctive intestinal neoplasms of domestic cats, previously thought to arise from enterochromaffin cells, were redefined as mast cell neoplasms. Although these tumors differed histologically from the more typical visceral mast cell neoplasm of cats, ultrastructural and histochemical similarities between cells comprising both tumors were encountered. Differences in granule morphology and histochemical characteristics were, however, consistently demonstrated when the neoplasms were compared. The intestinal neoplasms are not associated with ulceration of the gastrointestinal tract unlike many mast cell tumors involving viscera. We suggest that the differences between the cells in the typical visceral and intestinal tumors confirm and extend the concept of the existence of morphologic and functionally heterogeneous populations of mast cells occurring in different anatomical locations of the body.