Background Anal squamous cell carcinoma (ASCC) is preceded by persistent high-grade squamous intraepithelial lesion (HSIL). A small proportion of HSIL will progress to ASCC; estimates in men who have sex with men (MSM) suggest one in 400 per year in HIV-positive men and one in 4,000 per year in HIV-negative men. There are no tests to predict which HSIL are more likely to persist and potentially progress to ASCC. As MSM are often concurrently infected with multiple anal HPV genotypes, the role of each in progression to ASCC is unclear.

Methods Biopsies of suspected HSIL collected during high-resolution anoscopy from participants enrolled in the ongoing SPANC cohort of homosexual men (Sydney, Australia) between November 2010 and December 2011. Samples taken at 0, 6 and 12 months were formalin-fixed, paraffin-embedded then sandwich sectioned. Sections 1 and 5 were stained (haematoxylin and eosin [H&E]) and section 2 placed on a PEN-membrane slide. H&E sections were reviewed and lesions annotated using Aperio ScanScope software. Annotated abnormal tissue was isolated using laser capture microdissection (LCM), DNA was extracted and HPV genotypes present determined by reverse hybridisation assay (HPV SPF10-LiPA25, Labo Bio-medical Products).

Results From a pilot study comprising 16 men diagnosed with HSIL at one or more visits, 94% were positive for at least one HPV type. HPV16 was the most common genotype detected in HSIL (28%), followed by 45, 18 (each 17%), 58 (11%), 56, 31, 52, 34 and 33 (each 6%). Three participants had HSIL that persisted over three consecutive visits: 2 were positive for HPV16 and 1 for HPV18. An additional 28% of HSIL persisted for 2 consecutive visits, and were positive for HPV58 (40%), 16, 18 or 33 (each 20%).

Conclusion Overall, 10% of HSIL persisted for longer than 12 months with HPV16 being present in majority of these.