Cytopathology Update on Atypical Squamous Cells

In Brief The most common abnormality reported by cervical cytology (Pap tests) is atypical squamous cells (ASC). The two subcategories are ASC of undetermined significance (ASCUS) and ASC, cannot exclude high-grade squamous intraepithelial lesion (ASC-H). ASCUS show morphology suspicious for a low-grade lesion, while ASC-H cells are suspicious for a high-grade process. ASCUS account for most ASC reports, and the 2002 median ASCUS reporting rates were 3.1% for conventional smears and 4.1% for liquid-based preparations. Reporting rates for squamous intraepithelial lesions and cancer (SIL+) were also higher for liquid-based preparations, and thus the median ASC/SIL+ ratio was lower for liquid-based preparations (1.27) than for conventional smears (1.44). Interobserver reproducibility for ASC is generally considered lower than for other squamous epithelial abnormalities. Women with ASCUS may be managed by human papillomavirus DNA testing, repeated cytology, or colposcopy, while women with ASC-H should generally proceed to colposcopy. The most common epithelial abnormality in cervical cytology reports is atypical squamous cells, and this update provides relevant criteria, laboratory reporting practices, and management guidelines.