Evaluation of the atypical cytologic smear. Validity of the 1991 Bethesda System.

The 1991 Bethesda System states that atypical squamous or glandular cells of undetermined significance should be further classified as reactive or premalignant/malignant. The validity of this qualification for identification of patients with cervical intraepithelial neoplasia (CIN) was tested. One hundred twenty-four cytologic smears with squamous atypia were reviewed retrospectively by two cytopathologists blind to the colposcopy results. The smears were classified as favoring either reactive or premalignant/malignant processes. Subjective criteria used in the classification were based on the pathologists' experience. All patients underwent colposcopy and selected biopsy under the direction of a gynecologic oncologist. Of the 124 atypical smears, 69 were classified as favoring reactive processes and 55 as favoring premalignant/malignant processes by cytopathologist 1. Cytopathologist 2 classified 68 as reactive and 56 as premalignant/malignant. Colposcopy and selected biopsy revealed the following lesions: 34 cases of human papillomavirus (27.4%), 17 of CIN 1 (13.7%), 4 of CIN 2 (3.2%), 2 of CIN 3 (1.6%) and 67 without pathology (54.0%). All six patients with squamous atypia and underlying CIN 2 and 3 lesions had their cytology classified as premalignant/malignant by the cytopathologists. In these patients this qualification had high sensitivity (100%) and negative predictive value (100%). The 1991 Bethesda System classification above, when applied to patients with squamous atypia, was effective in identifying patients with serious pathologic cervical lesions. If used as a triage method, colposcopy should be reserved for atypical lesions classified as premalignant/malignant, potentially decreasing the cost of health care without decreasing the quality of that care.