Anal cancer is a leading neoplasia in people with immune impartments populations, and the lack of an accurate screening test challenges its prevention. Because the bacteria living in the anal epithelium the anal microbiota seems to influence and be influenced by cancer development, specific patterns of anal microbes could help in the diagnosis of precancerous anal lesions. We aimed to discover microbial biomarkers of anal precancer in high-risk populations. We discovered 12 proteins, previously reported to be associated with cancer progression, that were more abundant in the anal bacterial from subjects with precancerous lesions.