Malignant transformation and natural history of oral leukoplakia in 57,518 industrial workers of Gujarat, India.

In Gujarat, India, 6718 industrial workers, over 35 years of age, with oral leukoplakia (confirmed clinically and microscopically), were studied. After 2 years, 4762 (71%) of the individuals were re-examined. The buccal mucosa was the most common site of occurrence; 98.3% of these individuals had oral habits, with smoking alone or smoking in combination with "pan" or "supari" chewing accounting for 74.9% of the habit forms. Six individuals (0.13%) with oral leukoplakia developed oral carcinomas within 2 years. This incidence of malignant transformation was equivalent to 63/100,000 per year, which far exceeds that of new oral cancers expected even in high-risk populations. While 57.3% the leukoplakic lesions remained unchanged during a 2-year interval, 31.6% disappeared and 11% had an altered appearance. This study confirmed the precancerous nature of oral leukoplakia.