The aetiology and surgery of carcinoma of the anus, rectum and sigmoid colon in Crohn's disease. Negative correlation with human papillomavirus type 16 (HPV 16).

Anal and recto-sigmoid Crohn's disease may rarely be complicated by the development of local malignancy. Eight patients with this association were identified from the records of St. Mark's Hospital between 1947 and 1988 and two from The London Hospital. The aetiology of the malignancies and their surgical management have been examined. Eight patients had adenocarcinoma of the anus, rectum or sigmoid colon and two had squamous cell carcinoma of the anus. Synchronous dysplasia, adenomas and carcinomas were found in four of the eight patients with adenocarcinoma and a progression to malignancy which is analogous to that in ulcerative colitis is proposed for these cases via a 'dysplasia-carcinoma' or 'adenoma-carcinoma' sequence. In the four other patients with adenocarcinoma, the tumour arose within an area of Crohn's disease or in association with a chronic Crohn's fistula. In these four cases no dysplasia was found in the specimens at that time and long-standing infection is the only aetiological factor identified. Evidence for infection with human papillomavirus (HPV 16) was sought by DNA hybridisation of archival material but none was found in material from the Crohn's disease, fistulae or adeno- or squamous cell carcinomas. Anal and rectosigmoid Crohn's disease disguised the presence of malignancy, and diagnosis was usually delayed. All patients underwent excisional surgery and eight of the ten had all of the large bowel removed either as a single procedure or in stages. Only three of the eight cases of adenocarcinoma had early malignancies (Dukes' stage A) and the remaining five cases had locally advanced disease (Dukes' stage B).