Type V Pit Pattern and Submucosal Invasion of Early Stage of Colorectal Neoplasm

Abstract

Recent advances of magnifying colonoscopy have enabled detailed observation of colorectal neoplasms. We classified surface pit pattern into seven groups such as Type I, II, IIIL, IIIs, IV, VI and VN. Type I is round and regular in size and arrangement, histologically corresponding to normal glands or inflammatory ones. Type II is star shaped or onion-like shaped, larger in size than the normal pits, and is seen in the hyperplastic polyp. Type I and II are non-neoplastic pattern. In polypoid adenomas, the pits often look elongated (type IIIL; the “L” stands for “long” or “large”) and sometimes branched (type IV). Type IIIL is a pattern of tubular adenoma, generally, with a potential for branching. Type IV is a pattern of tubulovillous adenoma. Type IIIs (the “S” stands for “small” or “short”) pits are compactly arranged and smaller than the normal ones. This is the pattern of the depressed tumors, which tend to be early cancers. Lesions with type IIIS are not often detected, but are candidates of precursors of “de novo” cancers. The small pits reflect the straight and compactly arranged glands of the lesion. It presents intramucosal cancer or high grade dysplasia. In invasive cancer and in advanced cancer, the surface of the lesion becomes rough and often ulcerated; therefore it is almost devoid of epithelial cells. Type V divided into two subgroups, as type VI (I: irregular) and type VN (N: non-structure). Type VI reflects histological structural atypism outgrowth of cancerous glands, and type VN, which lacks of superficial microstructure, reflects exposing desmoplastic reaction of deeply invasive submucosal components to the surface. We evaluated 18128 colonic neoplasms taken at Akita Red Cross Hospital and Showa University Northern Yokohama Hospital from April 1992 to July 2007. There were no submucosal cancers of 13340 type IIIL lesions. Type IV pattern was seen in 3414 lesions and 76.3% of them were adenomas. Type IIIS pattern was seen in 292 lesions and 76.0% of them were adenomas. Type VI pattern was seen in 747 lesions and 70.8% of them were cancer. All of 335 type VN lesions were high grade dysplasia or cancer. We are able to estimate with a high degree of accuracy the histology of the lesion without taking biopsies from it by pit pattern diagnosis.