Oral cancer develops when abnormal cell development occurs in the mouth or throat. It is possible to develop cancerous growths on the inside of the lips, the inside of the mouth along the gums, the inside of the cheeks, and the inside of the tongue. If malignant tumors form near the bottom of the tongue, on the tonsils, the soft palate, or the lining of the throat, a diagnosis of oropharyngeal cancer is likely.