Macroscopic classification and kinetic alternations in the superficial lesion of colorectal neoplasms

Abstract

To clarify relation between macroscopic appearance and the mode of tumor growth in the superficial lesion of colorectal neoplasms, we compared their colonoscopic findings with histological architecture of tumor cells. Macroscopic type was classified into the superficial elevated lesion (IIa, n=42, mean 5.14mm) and the superficial depressed lesion (n=42, mean 3.84mm). The latter was further divided into 3 subtypes ; subtype A, an irregular depression with high marginal elevation (Dep (A), n=20) ; subtype B, an irregular depression with irregular marginal elevation (Dep (B), n=7) ; subtype C, a clear and wide depression without marginal elevation (Dep (C), n=15). Histological architecture was evaluated by the transmucosal growth index (TGI) of tumor cells, which is a ratio of tumor width contacting with the muscularis mucosae against that of tumor surface, and by the distribution of proliferating cells detected by Ki-67 antibody (MIB-1).
In adenomas TGI increased with a degree of central depression (IIa<Dep(A)<Dep(C)). In carcinomas TGI was high irrespective of their macroscopic forms. Ki-67 labeling indices tended to increase with histological atypia. Adenomas with severe atypia showed a high labeling consistent with carcinomas. In both adenomas and carcinomas, Ki-67 positive cells were mainly noted in upper third of neoplastic glands in IIa, Dep (A) and Dep (B) neoplasms. By contrast, Dep (C) neoplasms lost a preferential distribution of proliferating cells, which reached the whole neoplastic glands.
These results suggest that Dep (C) adenomas and carcinomas have a unique histopathological architecture in terms of a high TGI and an enlarged distribution of proliferating cells, implying a high malignant potential.