Quantitative assessment of normal and potentially premalignant epithelium at different levels of human colorectal crypts

Abstract

The present study uses morphometric techniques to assess whether altered differentiation patterns exist in PPM which might reflect its premalignant status. Samples were obtained from resected malignant lesions of large bowels of 10 Chinese patients. Normal (N) samples were biopsied from the margins of each resected large bowel. Potentially premalignant (PPM) mucosae were obtained from within 2 cm of the margins of the malignant lesions. Tissues were processed for histological examination and using strict criteria, colorectal crypts were divided into basal (B), intermediate (I) and surface (S) segments. Interactive digitisation of sections from each group was used to generate the following morphometric parameters in each segment: nuclear profile circularity indices (NSF and NCI); nuclear numerical density (N(A) and N(V)); the degree of deviation of the major nuclear axis in relation to the epithelial-connective junction (AGDMAX); cell height (CH); the distance between nuclear apex to cell apex (DNACA); the distance between cell base to nuclear apex (DCBNA); stratification index (SI) - the ratio of DCBNA and CH; and the volume density of mucous vacuoles in the reference epithelium (V(VMV,EP)). In comparisons of different segments within groups, the nuclei at the S segment of N and PPM crypts were more irregular and less circular in shape than nuclei from other segments. There was a shift of nuclear profile shape (NSF and NCI) from circular to ellipsiodal between B and S segments. In comparisons of similar segments between groups, no significant nuclear shape changes were detected in nuclei of PPM crypts when compared with nuclei in similar segments of N crypts and the pattern of nuclear shape alterations resembled those of normal crypts. In comparisons of different segments within groups of N and PPM crypts, AGDMAX. DNACA, DCBNA, CH and SI parameters demonstrated that epithelial cells at the I segments have more centrally positioned nuclei with the tallest epithelial height when compared with epithelial cells in other segments of both crypts. In B segments, nuclear N(A) and N(V) were almost double those of other segments in both N and PPM crypts, with marked reductions in these parameters between B and I segments. V(VMV,EP) was significantly highest in the I segment and significantly lowest in the S segment of both groups. Both N and PPM crypts showed similar trends in V(VMV,EP) within the crypt segments but when comparing similar segments between both crypts, a significant difference was detected only between S segments. The alterations of nuclear shape and packing densities, orientation and mucous content in N crypts were similarly expressed in PPM crypts and distinct differences in numerical density (N(V)) and stratification index existed in crypts between these two groups when comparing similar segments. All values in PPM were consistently lower when compared with N crypts. These preliminary observations may represent a subtly altered state of cellular differentiation in PPM which may be a reflection of early preneoplastic transformation.