Mucin abnormality of colonic mucosa in ulcerative colitis associated with carcinoma and/or dysplasia.

Twenty cases of resected specimens of carcinoma and/or dysplasia complicating ulcerative colitis were histochemically investigated by the periodic acid-thionein Schiff/potassium hydroxide/periodic acid-Schiff (PAT/KOH/PAS) staining method to see mucin characteristics of carcinoma, dysplasia, and the background mucosa of these lesions. As a control, 11 resected specimens of ulcerative colitis without dysplastic changes and 26 specimens of colonic carcinoma were examined also. All dysplasia and carcinoma in ulcerative colitis stained blue, whereas normal colonic mucin stained red in 65 percent. In 14 of 20 specimens with carcinoma and/or dysplasia, the background mucosa appeared normal with hematoxylin and eosin staining, but showed a mosaic staining pattern with PAT/KOH/PAS. However, only two of 11 specimens of ulcerative colitis without dysplasia and none of 26 specimens of flat mucosa with colorectal carcinoma showed a mosaic staining pattern. From these observations it was concluded that the PAT/KOH/PAS staining method could be useful as a histochemical marker of premalignant change in longstanding ulcerative colitis.