Although high-grade vulvar intraepithelial neoplasia (VIN III) is a clinically significant lesion, it can be overlooked because of nonspecific clinical findings and the fact that its cytomorphologic features mimic those of mild cervical intraepithelial neoplasia (CIN I).
To determine if there are cytomorphologic features on Papanicolaou tests that can reliably distinguish between VIN III and CIN I.
Papanicolaou tests diagnosed as CIN I from patients with biopsy-proven CIN I were compared with Papanicolaou tests diagnosed as CIN I from patients with biopsy-proven VIN III but with no biopsy-proven CIN I.
None of the cytomorphologic features evaluated could reliably distinguish CIN I from VIN III.
Since the Papanicolaou test cannot be used to distinguish between CIN I and VIN III, the clinician must pay careful attention to the clinical and colposcopic findings. Further research evaluating the use of ancillary studies, such as human papillomavirus typing, may be useful.