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 deter mine whether cytological parameters on Pap smears with a diagnosis of squamous atypia could be useful in predicting the presence of a squamo us intraepithelial lesion (SIL). Methods: For a 3-mo period, all patie nts who had a colposcopically directed biopsy and or endocervical cure ttage (ECC) with a simultaneous or a previous Pap smear showing squamo us atypia were identified. All biopsies were reviewed and all cytologi cal smears were evaluated for the following cytological parameters: in flammation, parakeratosis, atypical parakeratosis, number of atypical cells, nuclear size, chromatin pattern (fine, coarse, or hyperchromati c), as well as presence of metaplasia, nuclear membrane irregularity, multinucleation, and nuclear halo in the atypical cells. Results: a to tal of 97 patients were eligible for the study. The average interval b etween 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%) we re SIL, low grade, and 13 (13%) were SIL, high grade. Of the 67 that s howed 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 3 0% of the patients with any particular feature showing SIL on histolog y. 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 s mears appears a marker of an underlying SIL in a considerable number o f cases, and coarse chromatin seems most helpful in predicting the pre sence of SIL.