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A benign tumor is a tumor that lacks all three of the malignant properties of a cancer. Thus, by definition, a benign tumor:# does not grow in an unlimited, aggressive manner
# does not invade surrounding tissues
# does not metastasize
Classification The term "tumor" literally means "swelling", and the broadest definition of "benign tumor" encompasses all abnormal tissue masses which are not cancers. In practice, most of these entities are neoplasms, meaning that they contain a discrete population of cells which proliferate in an independent manner, usually as the result of acquired genetic abnormalities. Entities which may be referred to as "tumors" but are non-neoplastic include developmental abnormalities, such as hamartomas and ectopic rests (normal tissue in an anatomically abnormal location).Benign neoplasms are typically composed of cells which bear a strong resemblance to a normal cell type in their organ of origin. These tumors are named for the cell or tissue type from which they originate, followed by the suffix "-oma" (but not -carcinoma, -sarcoma, or -blastoma, which are generally cancers). For example, a lipoma is a common benign tumor of fat cells (lipocytes), and a chondroma is a benign tumor of cartilage-forming cells (chondrocytes). Adenomas are benign tumors of gland-forming cells, and are usually specified further by their cell or organ of origin, as in hepatic adenoma (a benign tumor of hepatocytes, or liver cells). There are a few cancers with 'benign-sounding' names which have been retained for historical reasons, including melanoma (a cancer of pigmented skin cells, or melanocytes) and seminoma (a cancer of male reproductive cells).In some cases, certain "benign" tumors may later give rise to malignant cancers, which result from additional genetic changes in a subpopulation of the tumor's neoplastic cells. A prominent example of this phenomenon is the tubular adenoma, a common type of colon polyp which is an important precursor to colon cancer. The cells in tubular adenomas, like most tumors which frequently progess to cancer, show certain abnormalities of cell maturation and appearance collectively known as dysplasia. These cellular abnormalities and are not seen in benign tumors that rarely or never turn cancerous, but are seen in other pre-cancerous tissue abnormalities which do not form discrete masses, such as pre-cancerous lesions of the uterine cervix. Some authorities prefer to refer to dysplastic tumors as "pre-malignant", and reserve the term "benign" for tumors which rarely or never give rise to cancer.
Signs and symptoms Benign tumors are very diverse, and may be asymptomatic or may cause specific symptoms depending on their anatomic location and tissue type. Symptoms or pathological effects of some benign tumors may include:
Treatment Many benign tumors do not need to be treated at all. If a benign tumor is causing symptoms, presents a health risk, or causes a cosmetic concern for the patient, surgery is usually the most effective approach. Most benign tumors do not respond to chemotherapy or radiation therapy, although there are exceptions.
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