Evidence implicating human papillomavirus in bladder carcinogenesis: A case-control study.

4594 Background: The etiology of high-risk oncogenic human papillomavirus (HPV) subtypes with signature cytomorphological changes such as koilocytosis in bladder cancer (BCa) carcinogenesis still remains controversial and insufficiently investigated. We evaluated the diagnostic concordance rate between HPV-DNA test with urine HPV related cytomorphological findings in BCa urine samples. Methods: A retrospective case-control study was conducted. A total of 172 HPV-positive urine cytology specimens from patients with primary BCa treated at our hospital between January 2020 and December 2024 were included as the study group. During the same period, of 172 HPV - negative urine cytology specimens from primary BCa were selected as the control group. HPV DNA was detected by in situ hybridization was utilized. Immunohistochemistry (IHC) was performed to assess p16 INK4a protein expression as a surrogate marker of functional HPV activity. Cytomorphologic changes that had concurrent liquid-base cytology were identified using The Paris System for Reporting Urinary Cytology (TPS) criteria. Statistical analyses were performed using chi-square tests and fisher's exact tests. Results: Overexpression of p16 INK4a was observed in 82.2% (140/172) of the HPV-positive group and showed a high level of concordance with HPV infection status (Kappa=0.812, p<0.001). Among the HPV-positive group, high-risk HPV types accounted for 88.9% (152/172) with HPV-16 (114/152,75.6%) and HPV-18 (38/152,24.4%) being the predominant subtypes. A p16INK4a protein expression from HPV-negative group was detected which was significantly lower than in the positive group (13/172, 7.56%, p<0.001). HPV infection cytomorphology was identified, with 48.6% (83/172) koilocytes (52/172, 30.23%) either alone or in addition to basaloid clusters (16/172, 9.3%) and atypical squamous cells (ASCs) (15/172, 8.72%) identified using TPS from the HPV-positive group, and a significantly lower rate of 6.1% (10/172, p<0.001) was identified from the HPV-negative group. Conclusions: HPV plays an etiological role in carcinogenesis and contributes to a worse prognosis for patients with BCa development. The identification of cytomorphologic changes in urine cytology is a significant and underutilized piece of etiological evidence supporting a role for HPV in bladder carcinogenesis. It provides a reliable direct and visible link between the viral cytopathic effect and the urothelial cells. Integrating routine cytological assessment with modern molecular testing in urine samples could better define its role as an oncogenic driver in specific BCa variants. Recognizing this association has implications for risk stratification, screening in high-risk populations, and potential therapeutic avenues.