CLONAL ANALYSIS OF HIGH-GRADE SQUAMOUS INTRAEPITHELIAL LESIONS OF THEUTERINE CERVIX

We previously reported that invasive squamous cell carcinomas of the u terine cervix are of monoclonal composition. In the current study, we extended our previous work to determine the clonal composition of case s of high-grade squamous intra-epithelial lesion (HSIL). Clonal analys is targeting the HUMARA locus was performed on cervical tissue from 9 cases, 8 showing heterozygosity at the HUMARA locus and being, therefo re, informative for clonality analysis. Uterine cervices were cut into IZ blocks, fixed with formalin and embedded in paraffin, and DNA was extracted from targeted lesions of each block. A total of 30 samples o f cervical intra-epithelial neoplasia 3 (CIN3) (14 samples of carcinom a in situ and 16 samples of severe dysplasia) and I sample of CIN2 (mo derate dysplasia) were analyzed. Monoclonal composition of the lesions was demonstrated in 30/30 cases of CIN3. Polyclonal composition was s een in the single case of CIN2. In 6 uterine cervices, in which dyspla stic lesions were present in move than 3 blocks, the pattern of X-chro mosome inactivation was the same in all lesions, suggesting that these individual lesions were derived from a single cell, with intraepithel ial extension within the cervical mucosa. By contrast, one uterus cont ained 2 discontinuous dysplastic foci with different patterns of X-chr omosome inactivation, indicating that the 2 lesions developed independ ently from each other. Our results demonstrate that (i) lesions of CIN 3 (severe dysplasia and carcinoma in site) are composed of a clonal ne oplastic population of cells and (ii) most cases of HSIL are unifocal in origin. (C) 1997 Wiley-Liss, Inc.