Comparison of Human Papillomavirus RNA In Situ Hybridization and p16 Immunostaining in Diagnostically Challenging High-Grade Squamous Intraepithelial Lesions in the Background of Atrophy

Human papillomavirus (HPV) in the postmenopausal age group is complex, with infected patients in this age group at increased risk of progressing to invasive disease and showing decreased clearance of the virus. Additionally, atrophic changes of the cervix can make histologic distinction of high-grade squamous intraepithelial lesions (HSILs) difficult. To determine morphologic and ancillary testing characteristics of atrophy and HSIL in postmenopausal patients. Files of patients at least 65 years of age were examined, with 81 patients (109 cases [53 benign, 56 HSIL]) included in the study. Results of morphology, immunostaining (p16 and Ki-67), and HPV RNA in situ hybridization (ISH) were noted on all cases with available material. Atrophy was present in 96 of 109 cases (88%) overall. Coarse nuclear chromatin was noted in none of the benign cases, in 19 of 30 HSIL biopsies (63%), and in 24 of 26 HSIL excisions (92%). All benign cases were negative for p16 and ISH. In the HSIL cases, 45 of 53 (89%) were positive for p16, and of cases with sufficient tissue for ISH, 44 of 45 (98%) were positive. Of the ISH/p16 discordant cases (n = 7), most were p16 negative/ISH positive (6 of 7; 86%), whereas 1 of 7 (14%) was p16 positive and ISH negative. A majority of HSIL cases showed near-full-thickness elevation of Ki-67 (45 of 54; 83%), whereas mitotic figures were less elevated. In postmenopausal patients with HSIL, mitotic activity is not reliably elevated, but Ki-67 is consistently high. ISH is a more direct method of HPV detection and should be considered in cases where morphology and immunolabeling show discordance.