Negative cone biopsies after colposcopy and their prediction.

A retrospective study of 899 cone biopsies revealed significantly more cones containing no dysplastic epithelium in patients who had a prior colposcopic assessment compared with those who had not been so assessed. A case-control study of 48 'negative' cones, 47 cones containing intraepithelial neoplasia (CIN), 44 microcarcinoma containing cones and 27 occult Ib containing cones has allowed five variables to be identified which can predict the presence of dysplastic or neoplastic tissue in the cone specimen. These variables include a colposcopic suspicion of invasion; a positive or worse pre-cone smear; two severely dyskaryotic smears within a 12-month observation period, previous abnormal histology and previous treatment for CIN. Using these criteria, 44% of 'negative' cones could be avoided without overlooking any cases of microcarcinoma or occult carcinoma.