The frequency and distribution of mitotic figures in dysplasia and carcinoma in situ.

The frequency and topographical (i.e. vertical and lateral) distribution of mitotic figures in normal cervical epithelium as well as in various degrees of dysplasia and in carcinoma in situ, was studied in punch biopsies and in subsequent cone specimens from 40 patients. The frequency of cells in mitosis in the whole thickness of the epithelium increased step-wise from normal epithelium to slight-moderate dysplasia, severe dysplasia and carcinoma in situ. A difference in the frequency of mitotic figures between slight and moderate dysplasia was recorded in the superficial cell layers of the epithelium. These findings, together with earlier reported differences in the frequency of DNA synthetizing cells between the various epithelial alterations support the validity of the histological classification of cervical atypias. Areas with mitosis alternated with areas without mitosis, supporting even here previous autoradiographical findings. The possible co-existence of proliferative and non-proliferative epithelial compartments in dysplasia and in carcinoma in situ of the uterine cervix is suggested.