Histocytological study of squamous atypia on Pap smears

The significance of squamous atypia on Pap smears is currently unclear and its management is controversial. We undertook this study to determine whether cytological parameters on Pap smears with a diagnosis of squamous atypia could be useful in predicting the presence of a squamous intraepithelial lesion (SIL).

For a 3-mo period, all patients who had a colposcopically directed biopsy and or endocervical curettage (ECC) with a simultaneous or a previous Pap smear showing squamous atypia were identified. All biopsies were reviewed and all cytological smears were evaluated for the following cytological parameters: inflammation, parakeratosis, atypical parakeratosis, number of atypical cells, nuclear size, chromatin pattern (fine, coarse, or hyperchromatic), as well as presence of metaplasia, nuclear membrane irregularity, multinucleation, and nuclear halo in the atypical cells.

a total of 97 patients were eligible for the study. The average interval between the Pap smear and colposcopy was 96 days (range, 0 to 364 days). Thirty patients (31%) had SIL on biopsy or ECC, of which 17 (18%) were SIL, low grade, and 13 (13%) were SIL, high grade. Of the 67 that showed no SIL on histology, 24 had inflammatory reactive changes, five had squamous metaplasia with atypia, one had parakeratosis, and 37 had essentially normal biopsies. Most of the cytological features, except coarse chromatin, were equally predictive of SIL with approximately 30% of the patients with any particular feature showing SIL on histology. However, 46% (17/37) of those that had coarse chromatin showed SIL on histology (P < 0.02). Based on this study, squamous atypia on Pap smears appears a marker of an underlying SIL in a considerable number of cases, and coarse chromatin seems most helpful in predicting the presence of SIL.