Successful sphincter-sparing local excision for mucinous adenocarcinoma associated with chronic fistula in ano using preoperative MRI evaluation.

A 78-year-old man with a 10-year history of ischiorectal abscess was referred to our hospital because purulent drainage from an external opening changed to mucoid drainage. By the brushing cytology of fistula ano, mucinous adenocarcinoma was found. T2-weighted magnetic resonance imaging (MRI) indicated that a mucinous adenocarcinoma was localized within the abscess and the fistula, and was not invasive neoplasm. He underwent a sphincter-sparing local excision of the ischiorectal abscess including the fistula and openings. The pathological findings indicated that mucinous adenocarcinoma arose from anal glands, developed lining the preexisting abscess and fistula wall. Five years after the resection, he remains asymptomatic and free of disease. From the present case, it is advisable that a high index of clinical suspicion in any elderly patient presenting with perirectal abscess and a major impact of the MRI evaluation on the perioperative assessment of perianal diseases should be emphasized.