Perianal fistula is a very debilitating event and a cause of morbidity in patients with Crohn's disease (CD). Its malignant transformation is very rare with an incidence of around 0.004-0.7$. Presence of disease in the colon and rectum is the major risk factor for the development of a perianal fistula. In this report we show a case of adenocarcinoma arising from a perianal fistulizing CD. This type of tumor is highly aggressive, difficult to diagnose, and has a rather poor prognosis. The different neoplastic transformations and the different types of tumors that may appear in patients with CD, especially at the colorectal level or at the level of an eventual anastomosis, are to date well documented and described in the literature, while there is a lack of information and of treated cases concerning the occurrence of cancer at the level of a fistula. Due to the rarity of cases, we tried to identify the most frequent and important risk factors: sex, duration of disease, age at diagnosis, and the history of the fistula.
Keywords: Adenocarcinoma; Crohn's disease; Perianal fistula.