Enlarged squamous cell nuclei in cervical cytologic specimens from perimenopausal women ("PM Cells") : a cause of ASC overdiagnosis.

We studied the appropriateness of interpreting squamous cells with enlarged, smooth, bland nuclei in perimenopausal women ("PM cells") as atypical squamous cells (ASCs). Papanicolaou smears (Paps) from 100 women (40-55 years old) with a cytologic interpretation of ASC of undetermined significance (ASCUS) and human papillomavirus (HPV) testing or a biopsy within 6 months were reviewed by 2 observers without knowledge of the biopsy diagnosis or HPV results. Cases in which both reviewers agreed that the Paps were diagnosed more properly as "negative for intraepithelial lesion or malignancy" were compared with cases of "true ASCUS," using histologic squamous intraepithelial lesion and/or a positive high-risk HPV test as a positive outcome (abnormal follow-up). Of 100 cases, 28 were reclassified as benign by both observers. In 15 of these, the original ASCUS interpretation was based on cells with bland nuclear enlargement (2-3 times the area of intermediate cell nuclei), smooth nuclear membranes, and fine chromatin. Abnormal follow-up was identified in 1 (7%) of 15 benign cases but in 30 (42%) of 72 true ASCUS cases (P = .023). PM cells are a significant cause of ASC overdiagnosis in women 40 to 55 years old. Cervical Paps with cells no more atypical than these can be interpreted safely as negative for intraepithelial lesion or malignancy.