Distribution of cervical intraepithelial neoplasia on the cervix in Chinese women: pooled analysis of 19 population based screening studies.

Background: Controversy remains whether a pattern of cervical intraepithelial neoplasia exists on the cervix. Our study aims at determining if the prevalence of histologically proven lesions differs by cervical four-quadrant location or by 12 o'clock surface locations of diagnosis.
Methods: We conducted a retrospective, histopathological study of 19 different population based cervical cancer screening studies from 1999 to 2010 by Cancer Hospital of Chinese Academy of Medical Sciences. The Institutional Review Board for human research subjects at CHCAMS approved all of the studies. During the colposcopy procedure, participant received either 4-quadrant biopsy or directed biopsy with/without endocervical curettage. Data of all samples were stratified by the methods of sampling. Kruskal-Wallis test was used to determine overall distribution of normal/CIN1, CIN2 and CIN3+ on the cervix.
Results: In total, 53,088 cervical samples were included in distribution analysis. 66.9% samples were obtained by random biopsy, 16.1% were by directed biopsy, and 17.0% were by endocervical curettage. 95.9%of the biopsied samples were diagnosed as normal/CIN1, 2.0% were CIN2, and 2.1% were CIN3+. CIN2 and CIN3+ were most often found in quadrants 2 and 3 (χKW2=46.6540, p<0.0001) and at the 4- and 7-o'clock positions by directed biopsy (ORCIN2=2.572, 1.689, ORCIN3+=3.481, 1.678, respectively), and at the 5-, 6-, 7-, 9- and 12-o'clock positions by random biopsy. CIN3+ was least often found at the 11-o'clock position by directed biopsy (OR=0.608).
Conclusions: Our results suggest a predisposition of specific locations on the cervix to CIN occurrence. Quadrants 2 and 3, especially the 4- and 7-o'clock positions should be preferentially targeted during biopsy. The decision for random biopsy should be reconsidered in future studies.