ABSTRACT
The clinical notes and histology of 374 patients treated by colectomy and ileo-rectal anastomosis for ulcerative colitis were reviewed. Only those with definite diagnosis of ulcerative colitis and follow-up rectal biopsies were included (171 cases). Morphology and patterns of mucin secretion were investigated to assess whether abnormal mucin with predominance of sialomucins is a useful indicator of malignancy-risk. Carcinoma has developed in six patients and 'precancer' in seven. The results show coexistence of dysplasia and sialomucin even in the absence of inflammation in all but three biopsies; in contrast the presence of both dysplasia and normal mucin profile was found in less than 1%. A significant correlation was noted between an inflamed mucosa and the development of cancer or precancer, the presence of sialomucins and the appearance of dysplasia. Sialomucins showed a greater sensitivity in detecting cancer than dysplasia (75% versus 30%). However, dysplasia was notably more specific (94% compared with 50%), hence its greater predictive value as indicator of malignancy (50% as against 15% for a positive sialomucin result). Mucin stains on routine fixed paraffin-embedded tissue provide a simple screening method to sharpen the assessment of dysplasia and cancer-risk in patients with ulcerative colitis despite the limitations referred to above. The lack of definite evidence of dysplasia in four patients who developed malignancy without premalignant changes in the rectal biopsies emphasises the need for frequent multiple biopsies in patients with an ileo-rectal anastomosis for ulcerative colitis.
