From fistula to malignancy: rectal mucinous adenocarcinoma arising in a chronic perianal fistula, a rare diagnostic challenge

Abstract

Perianal fistula is a common surgical complaint that general surgeon frequently face in daily clinical practice. However, an adenocarcinoma arising from a fistula is an uncommon entity that has the propensity to mimic benign conditions leading to a delays in diagnosis and management. We present a case of a 42-year-old patient with long standing history of perianal fistula. Given the prolonged nature of his disease further investigations were warranted. While colonoscopy ruled out luminal disease, pelvic magnetic resonance imaging and deep tissue biopsies confirmed the diagnosis of invasive adenocarcinoma with focal mucinous component. The patient required neoadjuvant treatment followed by extra levator abdominoperineal excision and pelvic floor reconstruction. At 5-year follow up, the patient didn’t have local recurrence or distant metastasis.