| [ Summary ] |
A 70-years-old male visited our clinic and underwent surveillance colonoscopy two years after polypectomy. Colonoscopy showed a semi-pedunculated polyp, 9 mm in size, in the sigmoid colon. A depressed area was detected at the top of the polyp. A conventional view suggested submucosal deeply invasive cancer. Large, elongated vessels were detected in the depressed area. So-called chicken skin mucosa in addition to submucosal tumor like expansion was seen at the base of the polyp. In the depressed area, Narrow Band Imaging (NBI) with magnification revealed vessels irregular in density, shape and size, which were classified as type IIIB according to Sano's classification. On the other hand, the type II capillary pattern, which suggested adenoma through histology, was seen at the periphery of the depressed area. Based on the above magnifying NBI findings, an endoscopic diagnosis of a submucosal deeply invasive carcinoma (SM2 ; 1,000μm or deeper in depth) with adenomatous components was established. Additionally, magnifying chromoendoscopy with 0.02 % crystal violet staining exhibited type VI high grade pattern in the depressed area according to Kudo's classification, which suggested SM2 through endoscopic examination. However, since the area of irregular-micro round pit patterns, which is commonly seen in submucosal cancer with moderately differentiated adenocarcinoma was observed histologically, and since it was less than 5 mm in size, submucosal cancer with superficial invasion (SM1 ; less than 1,000μm in depth) could not be excluded. Moreover, the polyp exhibited a polypoid growth pattern, and was 9 mm in size. Therefore, a diagnostic EMR rather than radical surgery was conducted to determine treatment. Through histology, the removed lesion was diagnosed as an early cancer consisting of well and moderately differentiated adenocarcinoma without unfavorable histology associated nodal involvement such as lymphovascular invasion or budding. The horizontal and vertical margins of the resected specimen were free of cancer or adenoma. However, the estimation of depth of invasion was different from that for mucosal cancer with musculari mucosae involvement (MM) into submucosal invasive cancer (pSM1 ; 640μm, pSM2；1,550μm） as determined by expert gastrointestinal pathologists. This case is notable and valuable as a case report because it was difficult to formulate an accurate diagnosis of submucosal invasion through either endoscopic or histological means. |