A case of depressed - Type (O-IIc) squamous cell carcinoma in situ at the anal canal resected by endoscopic submucosal dissection as excisional biopsy

An 81-year-old woman presented to our hospital with positive fecal occult blood test. Colonoscopy (CS) detected a small polyp at the sigmoid colon. Follow-up CS performed one year later revealed an irregular flat depressed lesion of 25mm in diameter at the anal canal. Endoscopic biopsy revealed squamous cell carcinoma. The depressed lesion became more evident with indigo carmine spraying, and was depicted by narrow band imaging (NBI) as a brownish area. Magnifying endoscopy (ME) with NBI of the depressed area revealed irregular blood vessels, which resembled irregular intra-epithelial papillary capillary loop (IPCL) in the esophagus squamous cell carcinoma lesion. These tumor vessels were generally equivalent to B type vessel in the Japan Esophageal Society ME Classification. The anal border, which was close to the dentate line, was well demarcated on NBI. The lesion showed no apparent rigidity endoscopically, and its shape changed smoothly by air inflation. These observations indicated that the lesion was a mucosal carcinoma; therefore, we performed en bloc resection of the tumor by endoscopic submucosal dissection (ESD). The tumor was 0-H c type and 24mm in diameter. The pathological diagnosis was squamous cell carcinoma, pTis, lyO, vO, VM (-), HM (-). The frequency of anal canal cancer among colon cancers is 0.8% according to past literatures. Most of them are adenocarcinomas; squamous cell carcinoma is relatively rare. To our knowledge, this is the first report of depressed-type squamous cell carcinoma at the anal canal, which was treated by ESD.