Prevalence of high-risk human papillomavirus genotypes in retinoblastoma

Background The human papillomavirus (HPV) is an important aetiological agent in cancer but its involvement in retinoblastomas (RBs) is controversial. Methods 64 formalin-fixed paraffin-embedded tissue blocks and 19 fresh-frozen specimens were subjected to multiplex PCR using PGMY09/11 primers, HPV genotyping, non-isotopic in situ hybridisation and immunohistochemistry for pRb and p16(INK4a). Results 24% of RBs contained HPV DNA. 90% of HPV genotypes were of high-risk (HR) type and 10% were of intermediate-risk (IR) type. HR HPVs 45, 59, 68 and 52 were detected for the first time, as were IR HPVs 82 and 73. There was only one HPV 18-positive case. Interestingly, no low-risk genotypes were identified. Nine formalin-fixed paraffin-embedded HPV-positive cases showed nuclear HPV positivity by non-isotopic in situ hybridisation. Immunohistochemistry did not show pRb expression in 67% of cases. 34% expressed nuclear p16(INK4a), of which 20 cases were also positive for HPV by multiplex PCR. A statistically significant association between HPV and pRb expression status was observed (p=0.0001). The association of HPV with p16(INK4a) expression was also statistically significant (p=0.0001). Conclusions While the presence of HPV in a subset of RB was demonstrated, its role in carcinogenesis needs further elucidation.