Most lip and oral cavity cancers start in squamous cells, the thin, flat cells that line the lips and oral cavity. These are called squamous cell carcinomas. Cancer cells may spread into deeper tissue as cancer grows. Squamous cell carcinoma usually develops in areas of leukoplakia (white patches of cells that do not rub off).
Looking into few population statistics of oral cancer from Surveillance, Epidemiology and End Results Program (SEER) of NIH :
More information on cancer statistics can be found here. The website offers trends data, prevalence and comparative distribution data on most cancers. SEER is supported by the Surveillance Research Program (SRP) in NCI’s Division of Cancer Control and Population Sciences (DCCPS).