Investigation of 100 consecutive negative cone biopsies

To investigate the reasons for cone biopsies reported as not containing intraepithelial or invasive malignancy and thereby find ways to decrease their incidence.

One hundred cone biopsies reported as negative were identified out of a total of 436 consecutive cone biopsies. The patients' cytology, colposcopy and histology reports and cytology and histology slides were reviewed. Further opinions in cases of doubt were obtained in cytology and histology. In cone biopsies still considered negative after reviews, deeper levels were cut, exhausting all paraffin blocks. Follow up cytology, colposcopy and histology were reviewed.

Gynaecological oncology unit in a university teaching hospital.

After re-evaluation the final diagnoses of cone biopsies initially reported as negative were positive (n = 21), unsatisfactory (n = 27) and true negative (n = 51), with one case excluded because of insufficient material for review. The positive cases were diagnosed on review (n = 11) or extra levels (n = 10). The unsatisfactory cases were all due to denudation. The 51 true negative cases were divided into those which never had had histologic confirmation by punch biopsy or endocervical curettage (n = 47) and those with a previously confirmed histological abnormality (n = 4).

The number of negative cone biopsies can be reduced by: 1. taking Pap smears after correction of atrophy and inflammation; 2. more scrupulous colposcopy aimed at reducing the number of unsatisfactory colposcopies or misinterpreted colposcopic findings; this through examination should include the vagina and vulva; 3. confirmation of smear and colposcopic findings by biopsy prior to cold-knife conisation and performing a large loop excision of the transformation zone (LLETZ) for cases where there is a discrepancy between the smear abnormality and colposcopy/biopsy findings; 4. good quality cone biopsies using a technique that does not handle the mucosa and is performed after the mucosa has had time to regenerate following the colposcopic investigations; and 5. exhausting all blocks with multiple levels before reporting a cone biopsy as negative.