Comparative study of oral squamous cell carcinoma in Okinawa, Southern Japan and Sapporo in Hokkaido, Northern Japan; with special reference to human papillomavirus and Epstein-Barr virus infection.

In Okinawa, a subtropical island in Southern Japan, the incidence of oral squamous cell carcinoma is 1.5 times higher than that in mainland Japan. Sixty cases of oral squamous cell carcinoma from 1993 to 1996 in Okinawa and 42 cases over the same period in Sapporo were examined histologically. Human papillomavirus (HPV) and Epstein-Barr virus (EBV) were detected by polymerase chain reaction (PCR) amplification with primers specific for HPV and EBV. In situ hybridisations of the viruses were also carried out. In the case of Epstein-Barr virus, in situ PCR was also performed. Thirty-five (58.3%) Okinawan tumours were well-differentiated in type, but in Sapporo, 18 (42%) were of such type. In Okinawa, tumours of the mouth floor (10 cases, 16.7%) and oropharynx (12 cases, 20%) were frequently observed, whereas in Sapporo only five cases (12%) of each were found. HPV was demonstrated in 78% of Okinawan cases and 26.2% of Sapporon cases by PCR or non-isotopic in situ hybridisation (NISH). There were 76.6% (46 cases) of Okinawan and 38.1% (16 cases) of Sapporo cases positive for EBV by PCR. In only 12 Okinawan cases and 4 Sapporon cases, were positive signals demonstrated by in situ PCR on the cancer cells themselves. EBV was demonstrated in the large number of infiltrating lymphocytes, most of which were CD3+, and a few were CD19+. In Okinawa, HPV might be an important causative factor of oral squamous cell carcinoma and EBV a less important factor, whereas in Sapporo HPV and EBV might play only a small part in the aetiology of the tumour.