Mucosal dysplasia. A major predictor of cancer following ileorectal anastomosis.

Fifty patients with ulcerative colitis managed by colectomy and ileorectal anastomosis had rectal biopsies performed in the period 1967 to 1972. Follow-up information was available on all patients. Thirty-nine patients were reviewed and rectal biopsies performed in the 1980 to 1982 period. Three patients had developed rectal cancer in the period 1975 to 1980, and two rectal cancers were detected in the 1980 to 1982 follow-up period. All cancers occurred in patients with a diagnosis of moderate or severe dysplasia in biopsy specimens from the 1969 to 1972 period. The probability of developing rectal cancer after a diagnosis of moderate or severe dysplasia in this series reached 42 per cent at nine years from diagnosis.