Transitional mucosa of the colon and tumor growth factors.

Transitional mucosa of the colon is the tissue immediately adjacent to a cancer, which has histochemical and ultrastructural features similar to those seen in neoplasia. Therefore, it has been hypothesized in the past that this tissue represents the premalignant antecedent to colonic adenocarcinoma. Other investigators have disputed this explanation because similar changes are found adjacent to colonic lesions other than adenocarcinoma. The hypothesis offered here suggests that transitional mucosa may result from the paracrine influence of tumor growth factors released by the tumor. Candidate peptide hormones known to be produced by tumors are proposed, and a framework is outlined to explain the occurrence of transitional mucosa adjacent to non-neoplastic lesions. Transitional mucosa may be both a genuine reflection of the transformed phenotype and yet a "reactive" phenomenon secondary to the presence of the adjacent tumor.