Appropriate cone dimensions to achieve negative excision margins after large loop excision of transformation zone in the uterine cervix for cervical intraepithelial neoplasia.

Aims: To determine appropriate cone dimensions for predicting margin status after large loop excision of transformation zone (LLETZ) treatment.

Methods: An observational study performed at the Colposcopy Unit of a university hospital setting involving patients who underwent LLETZ conisation within a 1-year period. Data concerning the characteristics, cone dimensions, lesion grade and excision margins of the patients were recorded.

Results: The median age of the women (n = 61) was 38 years (18-53). LLETZ cone specimens had 36.1% of cervical intraepithelial neoplasia (CIN)2/3 lesion and 13.1% positive margins. Mean cone depth and volume were 10.9 mm and 2.3 cm(3), respectively. Multiple logistic regression for main predictors and after adjustment for age, parity and CIN severity showed that cone volume and length, cone base surface and proportion of excised volume had a significant effect on margin positivity. ROC analysis showed that optimal cut-off for cone volume was 2.1 cm(3) (87.5% sensitivity - 54.7% specificity) or 8.6% of initial cervical volume (75% sensitivity - 75.5% specificity), and for cone length it was 10 mm (100% sensitivity - 52.8% specificity). Optimal cut-off for cone base surface as percentage of ectocervical surface was 32.7% (75% sensitivity - 69.8% specificity).

Conclusions: These findings should be taken into consideration when planning the outer boundaries of excision and cervical tissue to be removed so as to achieve oncologically safe limits.