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A benign neoplasm is an abnormal growth or tumor consisting of cells that divide and reproduce independently of the surrounding normal tissue. Cells of a benign neoplasm do not possess the typical characteristics of malignancy. Although the cells in any neoplasm, benign or malignant, tend to proliferate more quickly and last for a longer time than the corresponding normal cells, the benign, neoplastic cells proliferate at a slower rate than malignant cells. Benign neoplasms do not infiltrate and invade the surrounding tissue, although they do expand locally. They do not proliferate in an unrestrained, destructive manner, and they do not spread through the blood stream to distant sites within the body.
The cellular characteristics of a benign neoplasm closely resemble those of the normal cells, not displaying the defective cellular maturation of malignant cells. Any body cell type can produce a benign neoplasm. A fibrous capsule, providing clear demarcation between the tumor and the normal tissue, usually surrounds a benign neoplasm. For this reason, benign tumors can be removed entirely. A benign neoplasm, if it is totally removed, will not grow back.
A benign neoplasm is typically named after its predominant cell type, followed by the suffix, "-oma". For example, a benign tumor of glial cells, which are support cells in the nervous system, is a glioma. In general, the "–oma" suffix implies the benign, nonprogressive nature of a neoplasm, although this may not always be the case. For example, cancer of the pigmented skin cells, called melanoma, is malignant.
Although many benign neoplasms are perfectly harmless, the term “benign” may be misleading. Benign neoplasms, though lacking in invasive potential, can cause significant, detrimental effects. Approximately 13,000 deaths occur per year in the United States secondary to benign tumors. Neoplasms of cells that typically produce a hormone or secretion in the body may overproduce these chemicals, which can cause a variety of health problems. In addition, the accelerated growth of a benign tumor may compress surrounding tissues, damaging or displacing them.
Some benign neoplasms degenerate into cancers, possibly due to additional mutations of the genetic material. For example, certain spots or moles of the skin can become cancerous over time. Many of these premalignant areas progressively show abnormal development over time, a condition called dysplasia. Most physicians recommend excision of dysplastic lesions before they reach the malignant stage.
The symptoms of a benign tumor depend on its size, location, and properties. In addition to pain, pressure, and hormonal imbalances, symptoms may include abnormal bleeding, blockage of blood flow, itching, and cosmetic alterations. Colon polyps may impede the normal movement of waste materials through the colon, producing abdominal pain and swelling. Expanding tumors may erode or weaken bone, leading to fractures from seemingly minor trauma. Asymptomatic neoplasms do not require treatment, but surgical excision of the entire benign neoplasm is the treatment of choice when the patient experiences symptoms.