Pap smears of patients with extramammary Paget's disease of the vulva.

Extramammary Paget's disease (EMPD) of the vulva is a rare entity. The diagnosis is almost always made on biopsy. Tumor cells are seen rarely in Papanicolaou (Pap) smears. We encountered three cases of EMPD that were detected in Pap smears. One patient had vulvar and vaginal involvement and the abnormal cells seen in the vaginal smear initially were interpreted as high-grade squamous intraepithelial lesion. Retrospective review showed scattered single atypical cells with enlarged hyperchromatic nuclei, coarse chromatin, inconspicuous nucleoli, high nuclear/cytoplasmic (N:C) ratio, and scanty basophilic cytoplasm. Rare signet ring cells and cells within cells were present. In the other two patients who had cervical involvement, the correct diagnosis was made on Pap smears. The slides showed both single and cohesive sheets of glandular cells with enlarged round to oval nuclei, coarse chromatin, prominent nucleoli, and abundant basophilic cytoplasm containing prominent vacuoles with signet ring-cell appearance. Cells within cells were abundant. EMPD has distinct cytomorphological features. Although infrequently encountered, EMPD can be diagnosed on Pap smears with adequate clinical history.