Histochemical analysis of mucous cells of congenital adenomatoid malformation of the lung: Insights into the carcinogenesis of pulmonary adenocarcinoma expressing gastric mucins

Adenocarcinomas expressing gastric mucins often are accompanied by ectopic gastric mucosa or pyloric metaplasia. We have previously described mucinous bronchioloalveolar carcinoma (mucinous BAC) producing gastric mucins. In the lung tissue, mucous cells seemingly similar to gastric mucous cells are present in congenital adenomatoid malformation (CAM). We assessed 26 cases of CAM morphologically and histochemically. Mucous cells were detected in 12 of 26 cases. These mucous cells displayed papillary growth in cystic spaces and proliferated along alveolar walls. Mucous cells in the papillary configuration stained with galactose oxidase cold thionine Schiff reaction, and those in indented portions stained with paradoxical concanavalin A stain in all 8 cases and with pepsinogen II in 5 of 8 cases, which were available for histochemical analysis. Pepsinogen I was negative. Mucous cells in CAM were identical to those of pyloric mucosa and could be considered candidates for the origin of mucinous BAC producing gastric mucins.