Prevalence of anal intraepithelial neoplasia in patients with high-grade intraepithelial lesions of the lower genital tract.

High-risk HPV (hrHPV) infection is strongly associated with high-grade squamous intraepithelial lesions (HSILs) of the cervix, vagina, vulva, and anus, and with cancer (Moscicki et al., 2006; Crawford et al., 2011; Rietbergen et al., 2018). The prevalence of hrHPV in anal cancer is 85–91% (Plummer et al., 2016; Ebisch et al., 2017). Anal cancer is a disease in which malignant cells develop in the epithelial tissue of the anus. The incidence of anal squamous cell carcinoma (ASCC) has increased in many countries, in both sexes, a phenomenon mainly attributed to the increased sexual transmission of human papillomavirus (HPV) at the population level. Recent studies show that the prevalence of high-grade anal intraepithelial neoplasia (HSIL-AIN) reaches 13.4% in this specific group, while the detection of high-risk HPV in anal samples reaches 73%, with the HPV-16 genotype being the most frequent (Monti et al., 2023). Some systematic reviews corroborate that women with genital HSIL have a higher prevalence of anal HPV and dysplasia, even in non-immunosuppressed populations (Stier et al., 2015). It is also observed that HSIL-AIN are precursor lesions to anal cancer and, moreover, that patients undergoing treatment for anal HSIL have a progression rate to anal cancer almost 60% lower than those who underwent active monitoring and did not receive treatment, emphasizing the need for strong efforts in early detection of these lesions, prevention, and treatment. A second aspect of great relevance is the fact that the risk of anal canal neoplasia is higher in patients with high-grade vulvar, vaginal, and cervical neoplasia. Currently, studies on anal HPV infection, anal lesions, and SCCA have focused primarily on men, especially men who have sex with men (MSM), due to their high absolute risk of SCCA. Few studies have been conducted in women with anal intraepithelial neoplasia, and most have focused on HIV-infected women. Therefore, the effectiveness of different anal cancer screening methods in these patients needs to be determined. We have multiple screening techniques available in our setting with varying costs, accessibility, sensitivity, and specificity, including the use of high-resolution anoscopy (HRA) and anal cytology. This project investigates the prevalence of high-grade anal intraepithelial neoplasia (AIN2/3) and the detection of high-risk HPV in anal sites in patients with HSIL of the lower genital tract, as well as evaluating the sensitivity of anal HPV genotyping, anal cytology, and high-resolution anoscopy in the diagnosis of AIN. Furthermore, the implementation of “patient navigation,” that is, support geared towards efficient referral and reduction of barriers to diagnosis, has proven effective in cancer screening programs—especially for cervical and breast cancer—increasing screening rates by up to 64.5 percentage points (Community Preventive Services Task Force, 2024; Women’s Preventive Services Initiative, 2024). Although still incipient in the anal context, this approach shows strong potential to promote equity in access to HRA (high-resolution anoscopy) when indicated. Finally, the global scenario disrupts this priority: anal cancer is a neoplasm on the rise, with increasing incidence (Ebrahimi et al., 2024). In addition, anal cancer has shown a global increase in incidence, as evidenced by recent epidemiological data, approximately 90% of anal cancer cases are related to HPV (Ebrahimi, 2024; English, 2024).