Argyrophil cell microneoplasia in the Mastomys' stomach--an observation on early carcinoid formation.

To analyze the early stages of argyrophil cell carcinoid growth, complete serial sections were cut from the glandular portion of the stomachs of 22 Mastomys and submitted to Sevier-Munger's reaction. The 154 grossly invisible foci of argyrophil cell microproliferation thus detected were classified into three stages of microproliferations (I, II, and III), and the last stage was definitely a microcarcinoid. There was a gradual transition in cell proliferation among these three stages; the first stage (microproliferation I), in which the cells were morphologically indistinguishable from those of hyperplastic proliferation by general morphologic criteria, was where the initial change of argyrophil cell carcinoid formation was detectable by a light microscope. Whereas multiple occurrences of microcarcinoids accounted for the multiplicity of well-developed tumors in the stomachs of Mastomys, a well-developed carcinoid in this species was formed by the confluence of several microcarcinoids.