A 51-year-old man with familial adenomatous polyposis (FAP) and a history of 2-staged restorative proctocolectomy (RPC) with a stapled ileal pouch–anal anastomosis (IPAA) performed 15 years earlier was admitted to our department with a suspicion of malignancy within the anal transitional zone (ATZ). Histopathologic examination of colon specimens harvested during the primary surgery did not show the presence of malignancy. The patient did not attend the follow-up appointments after the operation. He had been experiencing anorectal pain and anal bleeding for 6 months before admission. Rectoscopy revealed an ATZ tumor that was subsequently identified as adenocarcinoma of G2 differentiation on histopathologic examination (Figure 1A). Magnetic resonance imaging (MRI) showed tumor infiltration into the mesorectum, sphincter complex, prostate, and the base of the penis (Figure 1B). Computed tomography (CT) showed no lymphatic or distant metastases. Extraintestinal manifestation of FAP was excluded on imaging (CT and MRI). The patient was referred for neoadjuvant radio- and chemotherapy. After treatment completion, control MRI demonstrated significant tumor regression, and the patient was scheduled for surgery. A total abdominoperineal excision (Miles procedure) with the ileal pouch and sphincter resection was successfully performed (radical R0 resection with histologically negative margins; Figure 1C and 1D). There was no indication for further adjuvant chemotherapy. The postoperative course was uneventful. A 12-month follow-up imaging examination showed no malignancy recurrence within the tumor field. However, several liver metastases were detected. Finally, the patient was scheduled for the FOLFOXIRI regimen (folinic acid, fluorouracil, oxaliplatin, and irinotecan). He did not respond effectively to the applied chemotherapy. Due to a lack of available treatment options and impaired general condition, the anticancer therapy was discontinued. The patient died several weeks later.

Figure 1. A familial adenomatous polyposis patient with advanced adenocarcinoma of the ileal pouch 15 years after the initial operation; A – microscopic image of adenocarcinoma G2 of the ileal pouch taken during rectoscopy (hematoxylin & eosin staining, magnification ×400); B – magnetic resonance imaging of the abdomen and pelvis showing a tumor infiltrating the mesorectal tissue, with invasion of the sphincter muscles, the prostate, and the base of the penis (arrows); C, D – intraoperative image of the ileal pouch during (C) and after resection (D); adenocarcinoma is indicated by the arrows.

The established treatment method for FAP patients is RPC. Some controversy exists about the proper pouch-anal anastomosis technique due to a risk of ATZ malignancy development.1 Pouch neoplasia is a rare long-term complication diagnosed in FAP patients undergoing RPC.2,3 A few risk factors for ileal pouch neoplasia have been identified: preservation of the residual rectal mucosa, a time interval of more than 10 years from RPC, and age over 44 years.2,4 These risk factors were present in our case. The reported risk of pouch adenoma development in FAP patients after RPC at 5, 10, and 15 years after the procedure is 7%, 35%, and 75%, respectively.5 Long-term endoscopic surveillance in FAP patients after RPC may allow for early-stage recognition of pouch neoplasia. The diagnosis of pouch neoplasia is a clinical challenge due to the long asymptomatic course and symptoms mimicking other entities, including pouchitis, which is the most common pouch-related complication.4,5

The risk of IPAA adenocarcinoma is very high, even many years after the initial surgical procedure. Therefore, lifelong follow-up and periodic pouch surveillance should be routinely performed.