Oral cancer in 57,518 industrial workers of Gujarat, India: a prevalence and followup study.

In Gujarat, India, 57,518 industrial workers over 35 years old were examined for oral lesions. At a two-year interval, 43,654 workers were re-examined. Biopsies were taken from 13,223 lesions. In the initial examination, 29 oral cancers were diagnosed, representing a prevalence rate of 50/100,000. After two years, 22 new oral cancers were diagnosed, representing an incidence rate of 25/100,000 per year. Over 90% were squamous carcinomas, with the majority of lesions occurring in the oropharynx and tongue. All patients who developed squamous carcinomas had tobacco habits, while 85% of the entire study population had oral habits in some form. Their most common habits were smoking tobacco alone or in combination with chewing "pan"/"supari." Of the carcinomas that developed during a two-year interval, 62% appeared in previously normal appearing mucosa. Leukoplakia was the only oral lesion that proved to be precancerous, with a transformation rate of 0.13% in a two-year interval.