Age-specific and age-standardised incidence rates for intraoral squamous cell carcinoma in blacks on the Witwatersrand, South Africa.

All new cases of intraoral squamous cell carcinoma which occurred in Blacks resident on the Witwatersrand during the 10-yr period 1971-80 were traced by examining the records of all the hospital pathology departments in this area. The population at risk at the mid-point of the study (1975) was calculated from the National Population Censuses of 1970 and 1980, and consisted of 1125960 men and 880269 women. Age-specific incidence rates and age-standardised incidence rates were calculated for each intraoral site for men and women. In the latter calculation a standard World population was used. All rates are expressed as average number of cases per 100000 population per annum. The age-specific incidence rates and age-standardised incidence rates (in brackets) for men and women respectively are: tongue, 1.43 and 0.26 (2.69 and 0.41); gingiva and alveolar ridge, 0.04 and 0.01 (0.07 and 0.01); floor of mouth, 0.87 and 0.22 (1.64 and 0.38); buccal mucosa, 0.05 and 0.04 (0.13 and 0.05); hard and soft palate, 0.34 and 0.05 (0.63 and 0.08). There appears to have been an increase in the incidence of intraoral cancer in Black South Africans since the first survey in 1953-55, which can probably be ascribed to the urbanization process. In Europe, North America and in other population groups in South Africa, the palate is least frequently affected. In contrast, in Black South Africans lesions of the palate are much more common, being less frequent only than tongue and floor of mouth lesions.(ABSTRACT TRUNCATED AT 250 WORDS)