Definition
A tumor is a locally instructed increase of the volume of tissue. That could be a localised mass or swelling for example caused by an edema, as well as a formation of new tissue. The latter is also known as neoplasia.
 
Most tumors of the oral cavity are benign tumors. A benign neoplasia often contains a capsule and/or a controlled cell growth of a cell population. 
 Malignant tumors manifest an uncontrolled cell growth, containing mutated cells, a destructive and tissue-infiltrating increase with formation of metastases. For the diagnosis, microscopic analysis is still the gold standard. 
 It is important for a dentist to recognize if a lesion needs to be biopsied before he starts a treatment. As a general rule, every suspicious lesion which persists for more than two weeks after the possible irritating factor has been removed, should be biopsied. 
Fibroma/ fibromatous lesions