Abstract

The relation of the secretory immunoglobulin system in the colon to colorectal cancer and dysplasia has been examined by staining routine formalin-fixed, paraffin-embedded sections from cases of carcinoma, adenoma and ulcerative colitis for secretory component (SC), IgA and J chain. In carcinomas there was a close relation between SC synthesis and differentiation and a similar relation was apparent between SC synthesis and degrees of dysplasia in adenomas. In both morphological and functional (SC synthesis) terms degrees of dysplasia in adenomas resembled degrees of differentiation in carcinomas suggesting that the essential "switch" in the progression towards neoplasia may occur at the level of the adenoma and that invasive malignancy can arise from dysplastic mucosa of varying severity. Actively regenerating mucosa in ulcerative colitis (UC) showed intense staining for SC as opposed to foci of precancerous dysplasia where, with one exception, staining was markedly reduced or absent, suggesting staining for SC could be useful in identifying foci of precancerous dysplasia in UC. In the absence of severe chronic inflammation, as in UC, the number of IgA-containing plasma cells was closely related to SC staining of neoplastic mucosa suggesting that SC may be important in the mechanism by which IgA lymphocytes home to the lamina propria of the colon.