LOW EPITHELIAL-CELL PROLIFERATION AND ABSENCE OF ONCOPROTEIN EXPRESSION IN JUVENILE POLYPOSIS OF THE STOMACH, WITH OR WITHOUT TUMORS

Objectives: To assess cell proliferation and analyze oncogenetic abnor malities in cases of juvenile polyposis of the stomach (JPs), with or without coexisting tumors. Methods: The Ki-67 labeling indices (KLI) w ere compared for juvenile polyps and coexisting tumors in three cases of JPs along with values for gastritis, foveolar epithelial hyperplast ic polyps, adenomas, and carcinomas. Expression of p53, Bcl-2, and c-E rbB-2 in tumors was examined immunohistochemically, and a search for c -Ki-ras mutations was made by DNA direct sequencing. Results: The KLI for JPs did not significantly differ between cases, being consistently lower than the values for both hyperplastic polyps and gastritis. The KLI for the papillary tumors and a signet ring cell carcinoma found i n association with JPs tended to be lower than those for their convent ional counterparts. P53, but not Bcl-2 and c-ErbB-2, was focally expre ssed in the papillary tumors, whereas all three were absent in the sig net ring cell carcinoma, in the JPs. No c-Ki-ras mutations were detect ed in the papillary tumors. Conclusions: The cell proliferation of JPs is relatively low and the polyps can be considered hamartomatous. How ever, neoplastic change clearly can occur in association with a relati ve increase in proliferative activity being observed in coexisting tum ors. Low cellular proliferative activity and absence of oncogenetic ab normalities in tumors of JPs, compared with their conventional counter part tumors, suggest that pathways of tumorigenesis and genetic altera tion in JPs may be different from those in their conventional counterp arts.