Endocrine cells and melanin-containing cells in the anal canal epithelium.

The epithelium of the anal canal from 22 humans was studied in order to demonstrate the possible presence of endocrine cells and melanin-containing cells. Histochemical methods aimed at demonstrating reducing substances, biogenic amines, argyrophilia and melanin, were used. Enterochromaffin cells, and possibly other types of endocrine cells, were demonstrated above the dentate line both in colo-rectal type epithelium and in the anal transitional zone. Melanin-containing cells could also occasionally be found in the anal transitional zone. The presence of endocrine cells in the anal canal epithelium opens up the possibility that carcinoids can originate in this region. Further, the presence of melanin-containing cells might explain the occurrence of malignant melanomas arising above the dentate line.