Growths can start in any area of the mouth, including bones, muscles, nerves and connective tissues, but they usually form on the lips, sides of the tongue, the soft palate and the floor of the mouth. Most oral growths like warts and oral candidiasis (thrush) are benign (not cancerous). Some types of oral tumors can become more serious. Most salivary gland tumors are slow-growing, benign and painless, although some can become cancerous.