High frequency of human papillomavirus 6/11, 16, and 18 infections in precancerous lesions and squamous cell carcinoma of the conjunctiva in subtropical Tanzania.

Dysplastic lesions and epithelial neoplasms of the conjunctiva account for approximately 2% of all malignant tumors in subtropical Tanzania. We examined the pathophysiologic role of human papillomavirus (HPV) in the development of conjunctival carcinoma in subtropical Tanzania, which has a high HPV prevalence. Tissue samples from 14 patients were obtained from the cancer registry archives at the medical center of the university in Dar es Salaam, Tanzania. A highly sensitive nonradioactive in situ hybridization technique (ImmunoMax) was applied to paraffin-embedded tissue samples to identify HPV DNA in conjunctival epithelial dysplasia and epithelial neoplasms. In each case, conventional morphologic evaluation revealed a transitional lesion extending from koilocytic dysplasia to severe dysplasia or invasive squamous cell carcinoma. Highly specific, morphologically easily distinguishable labeling of HPV-6/11, HPV-16, and HPV-18 was found in most cases. Coinfections were observed frequently. The signals showed varying intensities and different patterns of distribution. In general, higher signal intensity was found in dysplasia grades 1 and 2 and in well-differentiated areas of the invasive component of conjunctival carcinoma compared with less differentiated areas. This observation underlines the central role of HPV-16 and HPV-18 in the oncogenesis of conjunctival cancers in subtropical Tanzania.