Case report: late perianal mucinous adenocarcinoma after Crohn's disease proctectomy: an oncological rarity.

Background: As in ulcerative colitis, there is an increased incidence of colorectal carcinoma in Crohn's disease. While carcinoma formation originating from ano-rectal fistulas is generally considered as a rare event there are different publications reporting on mucinous adenocarcinoma formation in association with a neovagina and rectovaginal fistulas. To the best of our knowledge this is the first description of a perianal mucinous adenocarcinoma arising in a patient after Crohn's disease proctocolectomy.

Case Presentation: We report the case of a 50-year old female with a mucinous adenocarcinoma forming in the perineum eleven years after proctocolectomy for Crohn's disease. The patient was readmitted with perineal pain, leucocytosis and a perineal mass highly suspicious of abscess formation in the MRI-Scan. Histological examination revealed a mucinous adenocarcinoma. Exenteration including vagina, uterus and ovaries together with the coccygeal-bone was performed.

Conclusion: Mucinous adenocarcinoma formation is a rare complication of Crohn's disease and so far unreported after proctocolectomy.