Case ReportSynchronous mucinous adenocarcinoma of the recto sigmoid revealed by and seeding an anal fistula. (A case report and review of the literature)

•The diagnosis of such conditions remains difficult when the colonic tumor is unknown and the chronic lesion of anal fistula seems to be a benign condition.•The management of these cases remain controversial.•The aim of this study highlights the importance of high suspicion with further investigation and the need of biopsy in all anal fistulas.

IntroductionThere are few cases of synchronous rectal adenocarcinoma revealed by an anal fistula. The diagnosis of synchronous mucinous adenocarcinoma of the recto sigmoid and anal canal remains difficult. The chronic anal fistula can be mistaken as the common manifestation of a benign perianal abscess or fistula.Case presentationWe present a rare case of a Greek Caucasian 79 year old male patient with anal fistula and a recurrent perianal abscess who subsequently was found to have developed synchronous rectosigmoid and perianal mucinous adenocarcinoma on biopsy. The histological exam revealed mucinous adenocarcinoma in two sites, representing two tumors, cells were immunopositive for cytokeratin 20 and negative in cytokeratin 7. The patient underwent “laparoscopic extralevator abdominoperineal excision ” with both lesions being resected. There is no recurrence after four years of follow up.ConclusionsThis case highlights the importance of high suspicion, further investigation and the need of biopsy in all anal fistulae.