Is rectal carcinoid argyrophilic? Application of Grimelius' silver nitrate stain in four cases.

In four cases, small rectal carcinoids from patients who did not have accompanying significant clinical signs or metabolic disturbances were found to give a definite argyrophil reaction by double or triple impregnation of Grimelius' silver nitrate stain, but not by other silver methods for argyrophil or argentaffin granules, regardless of variations of cellular arrangement in ribbon-like, solid, and sclerosing patterns. The implication that the carcinoid tumor occurring in the rectum may constitute a group distinct from carcinoids arising from other sites is discussed.