[A case of primary carcinoma associated with anal fistula]

A 47-year-old man with no history of anal fistula was admitted to our hospital with a complaint of perianal pain. Computed tomography (CT) imaging revealed perianal abscess. Incision and drainage were performed under spinal anesthesia. Ten months after drainage, magnetic resonance imaging revealed anal fistula on the left side of the anus. Subsequently, core-out and seton procedures were performed for ischiorectalis type III anal fistula. Pathological examination of the resected specimen of anal fistula revealed a moderately differentiated adenocarcinoma, leading to the diagnosis of carcinoma associated with anal fistula. No distant metastases or enlarged lymph nodes were observed on positron emission tomography (PET)/CT. We performed abdominoperineal resection with wide resection of ischiorectalis fat tissue. The pathology results were tub2, A, ly0, v0, n0, PM0, DM0, RM0, H0, P0, M0, Stage II. Negative pressure wound therapy was performed for perineum deficiency, after which rapid wound healing was observed. Left inguinal lymph node recurrence was detected 8 months after surgery, for which radiotherapy was administered. Distant metastasis was detected 11 months after surgery. The patient died 21 months after surgery.