Characterisation of anal intraepithelial neoplasia and anal cancer in HIV‐positive men by immunohistochemical markers p16, Ki‐67, HPV‐E4 and DNA methylation markers

Human papillomavirus (HPV)‐induced anal intraepithelial neoplasia (AIN, graded 1‐3) is highly prevalent in HIV‐positive (HIV+) men who have sex with men (MSM), but only a minority of lesions progresses to cancer. Our study aimed to characterise comprehensively anal tissue samples from a cross‐sectional series (n = 104) of HIV+ MSM and longitudinal series (n = 40) of AIN2/3 progressing to cancer using different biomarkers. The cross‐sectional series consisted of 8 normal, 26 AIN1, 45 AIN2, 15 AIN3 and 10 anal squamous cell carcinoma. Tissue sections were immunohistochemically (IHC) stained for p16 (viral transformation marker), Ki‐67 (cellular proliferation marker) and HPV‐E4 (viral production marker). We evaluated the expression of IHC markers and compared it with DNA methylation, a marker for malignant transformation. E4 positivity decreased, whereas p16 and Ki‐67 scores and methylation marker positivity increased (P values