Immunocytochemical demonstration of enkephalin and beta-endorphin in endocrine tumors of the rectum. A survey of 27 colo-rectal carcinoids.

In a histopathological and immunocytochemical study of biopsy and/or operation specimens from 27 patients with endocrine tumors of the colon and rectum ("hind-gut carcinoids") enkephalin-immunoreactive tumor cells were observed in two cases. Both patients were obese women, about 50 years of age, with a history of constipation. The tumors were situated near the anus in the dorsal wall of the rectum. One tumor had metastasized to a lymph node, and the other showed vascular invasion. The tumor cells were non-argentaffin; some were argyrophil. One tumor contained only few enkephalin-immunoreactive cells but had numerous beta-endorphin-immunoreactive cells, which were distinct from the former. The other contained large numbers of enkephalin-immunoreactive cells but no beta-endorphin cells. Both tumors also harboured glucagon-immunoreactive cells; in one there were also cells containing immunoreactive pancreatic polypeptide. These cells were distinct from the enkephalin-storing ones. No 5-hydroxytryptamine could be detected in the two tumors.