RESUMO
INTRODUCTION: There 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 PRESENTATION: We present a rare case of a Greek Caucasian 79year 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. CONCLUSIONS: This case highlights the importance of high suspicion, further investigation and the need of biopsy in all anal fistulae.