Transitional mucosa of colon. A morphological, histochemical, and immunohistochemical study.

We studied alterations in the transitional mucosa of the colon in 18 cases of primary colonic adenocarcinoma (4 from the cecum; 4, the ascending colon; 5, the descending colon; 2, the sigmoid colon; and 3, the rectum). One patient had 2 separate primary tumors. Formalin-fixed, paraffin-embedded sections were studied in all cases, and tissues fixed in methacarn fixative were available in 9. Sections of tumor and transitional mucosa were compared with those of normal mucosa distant from the tumor. Sections were stained with hematoxylin-eosin, Masson's trichrome, and alcian blue at a pH of 0.9 (sulfomucin) and at a pH of 2.5 (sialomucin and sulfomucin). Immunoperoxidase stains for collagen type IV (basal lamina) were also performed. Transitional mucosa showed morphological alterations, including increase in mucosal thickness and crypt distortion. An increase in lamina propria fibrosis was noted in transitional mucosa in 3 cases. Abnormal mucin content, consisting of a predominance of sialomucin, was noted in transitional mucosa in 12 cases. In one of these, sialomucin was predominant in both transitional and normal mucosa. No alterations in the thickness of the subepithelial collagen table were noted. Collagen type IV staining was effective in demonstrating an increase in lamina propria vascularity in transitional mucosa in 11 specimens.