Epithelial cell abnormalities: Squamous

Abstract

Our understanding of preinvasive HPV-associated squamous lesions supports only two conceptual divisions: HPV infection and true precancer. Transient infections generally regress over the course of 1–2 years, and lesions with HPV persistence are associated with an increased risk of developing a cancer precursor (precancer) or invasive cancer. This concept led to the introduction of the two-tiered nomenclature of low-grade squamous intraepithelial lesion (LSIL) and high-grade squamous intraepithelial lesion (HSIL), by the Bethesda System (TBS) in 1988. The 2014 Bethesda update maintains this dichotomous reporting terminology for the squamous intraepithelial lesions. Since the focus of cervical cancer screening is primarily the detection of HSIL, this chapter has been substantially expanded to include problematic patterns and mimics that may lead to locator and/or interpretation errors of non-neoplastic changes as HSIL/ASC-H or vice versa.