Majority and minority cell populations in small-intestinal carcinoids.

A quantitative study of argentaffin and argyrophil cells in 12 typical small intestinal carcinoids was made. The tumours contained 20-74 per cent of argentaffin cells (mean, 59 per cent) and 11-64 per cent of argyrophil cells (mean, 28 per cent). Five to 37 per cent (mean, 13 per cent) were unreactive to both silver stains. The argentaffin cells constituted the majority cell population in all tumours except one, in which the argyrophil cells predominated. At electron microscopy, pleomorphic secretory granules of the enterochromaffin cell type were found in argentaffin tumour cells, while the argyrophil tumour cells contained round granules. The silver staining properties and the ultrastructural morphology of the small-intestinal carcinoids are consistent with the opinion that these tumours are multi-hormonal.