Increase of poorly proliferated p63 + /Ki67 + basal cells forming multiple layers in the aberrant remodeled epithelium in nasal polyps.

Background: Aberrant epithelial remodeling with the ectopic expression of p63 ( basal cell markers) is an important pathologic phenomenon seen in chronically inflamed airway epithelium such as in nasal polyps (NPs). Methods: Biopsies were obtained from 55 NP patients and 18 healthy controls ( inferior turbinate). Among NP patients, 15 were treated with oral and nasal steroids, so that two sets of NP biopsies were taken before and after the treatments. p63, Ki67, type IV beta-tubulin, and cell cycle markers were investigated in these specimens. Results: The number of p63(+) cells is significantly higher in both hyperplastic (1.53-fold, P < 0.0001) and squamous metaplastic (2.02- fold, P < 0.0001) epithelium from NPs than from healthy controls. There are three types of proliferative basal cells (p63(+)/Ki67(+)) which are in different phases of the cell cycle, such as G1 phase (type I cells), S to G2 phase (type II cells), and mitosis (type III cells). Of importance, some type I cells may arrest after proliferation although they may still be p63(+)/Ki67(+). In healthy epithelium, the ratio of the type I and II cells is almost 50: 50. However, less type II cells are found in hyperplastic epithelium (34.85%, P = 0.012) and in squamous metaplastic epithelium (30.77%, P = 0.02) together with the presence of type III cells (3.45%, P = 0.01). These findings were not changed after steroid treatments. Conclusions: An increase of poorly proliferated basal cells forming multiple layers, which may stain for basal cell markers but does not form a proper epidermal barrier, is an important histopathologic phenomenon in aberrant remodeled epithelium of NPs.