Mucous and argentaffin cells in colonic adenocarcinomas of tamarins and rats.

Primary and metastatic neoplasms of four naturally occurring colonic adenocarcinomas in the cotton-topped tamarin, Saguinus oedipus oedipus, and four chemically induced rat colonic adenocarcinomas were examined with light and electron microscopy. In each case, we observed mixtures of mucous and argentaffin cells in metastatic sites, proving that endocrine cells are an integral part of these tumors. The occurrence of mixed cell populations in metastases in both species suggests, but does not prove, that colonic tumor cells have the capacity for multi-directional differentiation and that neoplastic mucous and argentaffin cells in the colon have a common origin. We also observed mitotic figures in neoplastic argentaffin cells, confirming the observations of others that these cells can label with tritiated thymidine and divide.