Anal adenocarcinoma complicating chronic Crohn's disease

Colorectal adenocarcinoma and Crohn's disease are known to be associated entities. However, a carcinoma arising within a chronic perianal fistulous tract in a patient with Crohn's disease is a rare complication.

We present a case of a 40-year-old male patient with a long-standing perianal Crohn's disease who developed an anal mucinous adenocarcinoma within the fistulous tracts.

Although, Crohn's disease and colorectal carcinoma association is well established, few cases have been reported where the cancer has originated within a perianal fistula. Constant mucosal regeneration occurring within a fistula seems to be the predominant pathogenetic mechanism, while immunosuppressants and anti-TNF agents may also contribute to the malignant transformation. Unfortunately, the lack of suspicion and the inadequate physical examination or colonoscopy due to exacerbation of the perianal symptoms could lead to delayed diagnosis; and thus, a poor prognosis.

Albeit a rare complication, clinicians should maintain a high degree of vigilance about the possible development of adenocarcinoma in patients with long-standing perianal Crohn's disease. Thus, these patients should be kept under regular surveillance with examination under anaesthesia and biopsies or curettage of the tracts.