Cervical Cancer Screening: Histologic Outcomes of HPV-Negative HSIL/ASC-H Cytology in a Tertiary Referral Cohort in Northern Thailand

Background and Objectives: Cotesting combines cervical cytology and HPV testing and usually identifies HSIL/ASC-H in association with HPV positivity; however, a small subset shows discordant results with high-grade cytology but negative HPV testing. We evaluated the clinicopathologic significance and histologic outcomes of HPV-negative HSIL or ASC-H cytology in a tertiary referral setting. Materials and Methods: We retrospectively reviewed women referred to a tertiary colposcopy unit (January 2019–October 2025) with HPV-negative HSIL or ASC-H on cotesting. Clinical findings, colposcopy, histology, excisional procedures, and follow-up were abstracted. Cytology and histology were reviewed by an expert gynecologic pathologist, and p16 immunohistochemistry was performed in all cases. Results: Among 92 women with HSIL/ASC-H cytology who underwent cotesting, 84 were HPV-positive (35 HSIL, 49 ASC-H). Eight cases (8.7%) remained HPV-negative after cytology review: 2/37 (5.4%) HSIL and 6/55 (10.9%) ASC-H. On histology, 4/8 (50%) had HSIL (CIN3) and 4/8 had LSIL; all CIN3 cases showed diffuse block-type p16 positivity. Two of six HPV-negative ASC-H cases (33.3%) were CIN3. One patient had persistent high-grade disease requiring two excisional procedures during follow-up. Conclusions: HPV-negative HSIL/ASC-H cytology is uncommon but associated with a substantial risk of CIN3. The consistent p16 positivity in tissue-confirmed HSIL supports HPV-attributable disease and suggests that most discordant cases reflect false-negative HPV testing rather than HPV-independent pathology. High-grade cytology should prompt colposcopic evaluation regardless of HPV status, and management should not be de-escalated solely on the basis of a negative HPV test.