The transitional polyp of the colorectal mucosa

45 cases of small polypoid lesions occurring in the colorectal mucosa free of inflammatory or neoplastic disease are presented. The lesions were removed at colonoscopy and displayed neither features of hyperplastic (metaplastic) polyps nor features of a neoplastic proliferation. Morphologically these small lesions were characterized by elongated and widened crypts, enlarged goblet cells with an increase in mucous production. Histochemically there was a reversion of the usual pattern of mucin production in the colorectal mucosa: an increase in sialomucin production and a decrease in sulfomucins. Thus these lesions demonstrate the same morphological and histochemical features as the transitional mucosa surrounding carcinoma and adenoma in the large bowel. These "transitional" polyps could represent an early step in the development of neoplastic processes in the colorectal mucosa and precede adenomas.