Juvenile polyposis coli: a facultative precancerosis with some similarities to ulcerative colitis?

We investigated the case of a 13-year-old male with juvenile polyposis (JP) to determine the extent of intraepithelial neoplasia and associated genetic changes, as well as cellular proliferation, within these polyps using immunohistochemistry with antibodies against p53, bcl-2, and Ki-67. Examination of the total proctocolectomy specimen revealed 70 polyps. The 18 largest polyps were investigated microscopically and disclosed the typical hamartomas with frequent erosions of the surface epithelium and reparative changes. Only one polyp showed focal low-grade intraepithelial neoplasia. The immunohistochemical studies revealed an expression of p53 and an abnormal Ki-67 pattern of the surface epithelium only within the neoplastic area. These findings may hint at a possible pathogenetic mechanism for the evolution of colorectal cancer in JP. As in ulcerative colitis, carcinomas in JP may develop along a dysplasia-carcinoma sequence resulting from permanent mechanical insults, inflammation, and repair rather than from an adenoma-carcinoma sequence as in familial adenomatous polyposis (FAP).