False-positive squamous cell carcinoma in cervical smears: cytologic-histologic correlation in 19 cases.

Cytologic features of squamous intraepithelial lesions (SIL) can mimic those of invasive squamous-cell carcinoma. We compare and correlate the cytological findings of 19 false-positive squamous-cell carcinomas with follow-up cone biopsies or hysterectomy specimens to define which type of dysplasia is more prone to diagnostic errors on cervical Papanicolaou (Pap) smears. Out of 128 patients diagnosed with invasive squamous-cell carcinoma from 1994-2000, 19 (14.8%) with follow-up cone biopsies or hysterectomy specimens were false-positive cases, showing only cervical intraepithelial neoplasia (CIN). We reviewed tissue sections from these 19 cases of CIN for cytologic features of squamous-cell carcinoma, such as markedly pleomorphic and/or dysplastic squamous cells, necrosis, and nucleoli. Twelve of 19 patients (63%) were menopausal. The mean age was 50.5 yr. On review of cervical smears, 18 cases qualified for the cytologic diagnosis of squamous-cell carcinoma, keratinizing type, and one case qualified for squamous-cell carcinoma, nonkeratinizing type. Pleomorphic and/or keratinizing dysplasia was found in 15 out of 19 patients (79%), necrosis within superficial endocervical glands in 9 out of 19 patients (47%), and conspicuous nucleoli in 12 out of 19 patients (63%). One or more of these changes were seen in all but 2 patients (89%). Endocervical gland involvement was present and extensive in 18 of the 19 cases (94%). The mean age was older than expected for SIL (50.5 vs. a reported 40), and matched the mean age found in patients with invasive squamous-cell carcinoma. Pleomorphic and/or keratinizing dysplasia involving endocervical glands may exhibit the cytologic features of squamous-cell carcinoma on cervical Pap smears.