These tumors are usually of unknown etiology. They are classified as benign and malignant. Benign tumors are usually circumscribed, mobile on palpation, have smooth radiographic borders, do not metastasize, grow slowly and press without infiltrating the adjacent tissues. Malignant tumors, on the contrary, are firmly adherent to palpation, do not have smooth radiographic borders, metastasize, grow rapidly and invade adjacent tissues.