Carcinoid tumors with focal mucin production.

50 carcinoid tumors of different locations in the gastrointestinal and respiratory tracts were examined histochemically for mucin production. Isolated discrete aggregates of mucosubstances were identified in a large number of cases (46% of all carcinoid tumors, ranging from 53 to 36% in different organ locations). Acidity and composition of mucosubstances (sulfomucin vs. sialomucin contents) in carcinoids were not different from those described in their corresponding locations. These data support numerous other observations that point to a common stem cell precursor for both enterochromaffin and mucus-secreting epithelial cells in gastrointestinal and respiratory tract mucosal membranes. A shared endodermal derivation is favored over a separate neuroectodermal origin for the chromaffin cell system.