In an in vitro system the overlap behaviour of cultivated cells of human normal cervical epithelium, dysplasia, carcinoma in situ and invasive cervical carcinoma was examined with a quantitative method initiated by Abercrombie and his co-workers. The overlap index of cells from normal cervical epithelium was significantly lower than that of all other cells examined (p0.05).Likewise no significant differences were obtained f r o m comparison of overlap indices of cells of carcinoma in sit0 o r dysplasia and cervical carcinoma (p>0.05).The calculated low overlap index of cells cultivated from normal cervical epithelium i s a quantitative expression of the monolayering i n such cultures. The significant differences of overlap index between cells cultivated f r o m normal cervical epithelium and f r o m intraepithelial atypias and carcinomas of the cervix uteri, and the non-significant differences between intraepithelial atypias and cervical carcinomas, are Considered as an expression of the same biological deviation i n preinvasive and invasive lesions of the cervix uteri. Obviously, i n spite of the different morphology, dysplasia, carcinoma in situ and invasive carcinoma of the cervix uteri have biologically common features and the different morphological classification of the preinvaslve lesions of the cervix uteri does not always reflect their real lnvaslve potential.In the last 20 years normal and neoplastic epithelium from the human cervix uteri have been repeatedly investigated in tissue culture. The details and some results of these studies were reviewed by Wilbanks (1969Wilbanks ( , 1975Wilbanks ( , 1976 The human uterine cervix offers excellent possibilities for the study of the development of squamouscell carcinoma at different stages. Therefore it became interesting to carry out quantitative studies on nuclear overlap behaviour of cells from normal cervical epithelium, dysplasia, carcinoma in situ and cervical carcinoma cultivated in vitro.
MATERIAL AND METHODSAfter cytological and colposcopic classification and localization of areas of normal epithelium, dysplasia, carcinoma in situ or carcinoma of the cervix uteri, a biopsy was taken from such areas.The full details of the technique used have already been published (Ebeling et af., 1978). The biopsy was washed in Hanks' salt solution and split into two parts. One half was fixed for histological examination while the other was prepared for tissue culture. The epithelium was separated from the stroma and finely minced, then pieces of tissue 1 -1,s mm3 in size were placed under a coverslip in special glass culture chambers at a distance of about 1 cm from one another. All cultures were grown under the same conditions at 37" C in a 1:l mixture of Parker's medium 199 and Moore's RPMI medium with 15% foetal calf serum. The
