Histomorphometric characteristics and cellular kinetics of colorectal polyps with epithelial serrated proliferation adjacent to carcinoma

Four cases of colorectal polyps with epithelial serrated proliferation (CP- ESP) with malignant transformation were studied. In CP-ESP adjacent to carc inoma, if the nuclear size in the surface layer was significantly smaller t han those in the bottom and the middle layers of the crypts, the specimen w as defined as zone formation positive. If there was no significant differen ce among the layers, the specimen was defined as zone formation negative. C ell kinetics were evaluated using Ki-67 immunostaining. The CP-ESP regions of cases 1 and 2 showed zone formation with inferior and lateral glandular branching, and were qualitatively hyperplastic on eel kinetics. Cases 3 and 4 showed inferior and lateral glandular branching with no zone formation, and were kinetically neoplastic (adenoma). The histogenesis of hyper plasti c polyps with atypia (cases 1 and 2) involves the hyperplastic polyp-carcin oma sequence. In contrast, the development of tubulovillous adenoma or serr ated adenoma (cases 3 and 4) may involve the tubulovillous adenoma-carcinom a or serrated adenoma-carcinoma sequence.