Abstract
Carcinoma of the anal canal is classified as intra- or extramucosal, but preoperative diagnosis is often difficult because extramucosal carcinoma of the canal generally offers scant mucosal surface findings. The present case involved poorly differentiated squamous cell carcinoma of the anal canal presenting with an extramucosal development that made diagnosis difficult. A 70-year-old woman visited our hospital with a chief complaint of anal pain. Rectal examination showed circumferential stenosis 3 cm from the anal verge. A largely immobile induration was found on palpation, and was accompanied by pain. Lower gastrointestinal endoscopy showed scant changes in the mucosal surface, and biopsy tissue diagnosis from the stenotic area showed no obvious atypical cells or tumor cells. Transanal needle biopsy also failed to give a definitive diagnosis, and abdominoperineal resection of the rectum was implemented for diagnosis and treatment. The resected specimen exhibited tumor cells with an extramucosal distribution from the submucosal layer, centered on the transitional epithelium of the anal canal. Histopathological examination showed a scarce number of keratotic portions and intercellular bridges in one limited portion within the tumor. The patient was finally diagnosed with poorly differentiated squamous cell carcinoma.
