A benign tumor is a cell mass (tumor) that has no ability to invade neighboring tissue or metastasize. It does not spread to, or attack, nearby networks; however, can sometimes be very large. When removed, benign tumors usually do not grow back, whereas malignant tumors sometimes occur. Unlike most benign tumors elsewhere in the body, benign brain tumors can be life threatening. Benign tumors generally have slower rates of growth than malignant tumors and tumor cells are usually more differentiated (cells have normal features). They are usually surrounded by an outer surface (fibrous sheath from connective tissue) or fixed with epithelials. Common examples of benign tumors include moles and uterine fibroids.
Although benign tumors will not metastasize or invade local tissue, some types may still produce negative health effects. Benign tumor growth produces a "mass effect" that can suppress tissue and can cause nerve damage, reduced blood to the body area (ischemia), tissue death (necrosis) and organ damage. The health effects of the tumor may be more pronounced if the tumor is in an enclosed space such as a skull, respiratory tract, sinus or inside bone. Endocrine tissue tumors can produce excessive hormones, especially when cells are well differentiated. Examples include adrenocortical adenoma and thyroid adenoma.
Although most benign tumors are not life-threatening, many types of benign tumors have the potential to become cancerous (malignant) through a process known as tumor development. For this reason and other negative health effects, some benign tumors are removed surgically.
Video Benign tumor
Classification
Benign neoplasms are usually but not always composed of cells that have a strong resemblance to the normal cell types in their organs of origin. These tumors are named for the type of cell or tissue from which they originate, followed by the "-oma" suffix (but not-carcinoma, -sarcoma, or -blastoma, which is generally cancerous). For example, lipoma is a common benign tumor of fat cells (lipocytes), and chondroma is a benign tumor of cartilage-forming cells (chondrocytes). Adenomas are benign tumors of glandular cells, and are usually determined further by their original cells or organs, such as in liver adenomas (benign tumors of hepatocytes, or liver cells). Teratomas contain many types of cells such as skin, nerves, brain and thyroid, partly because they come from germ cells. Hamartomas are a group of benign tumors that have relatively normal cellular differentiation but irregular network architecture. There are several cancers with names that have been arrested for historical reasons, including melanoma (skin cancer pigmented cells, or melanocytes) and seminomas (male reproductive cancer cells). Skin tags, vowel polyps and colon hyperplastic polyps are often referred to as benign but are actually overgrowth of normal tissue rather than neoplasms.
Maps Benign tumor
Health effects
Benign tumors are very diverse, and may be asymptomatic or may cause specific symptoms depending on the location of the anatomy and the type of tissue. They grow out, producing large rounded mass, which can cause what is known as the "mass effect". This growth can cause compression of tissue or local organs, which can cause many effects such as channel blockage, decreased blood flow (ischemia), tissue death (necrosis) and pain or nerve damage. Some tumors also produce hormones that can cause life-threatening situations. Insulinoma can produce large amounts of insulin that leads to hypoglycemia. Pituitary adenomas can cause elevated levels of hormones such as growth hormone and growth factors such as insulin-1, which causes acromegaly; prolactin; ACTH and cortisol, which cause Cushing's disease; TSH, which causes hyperthyroidism; and FSH and LH. Intestinal intestus can occur with a variety of benign colonic tumors. Cosmetic effects can be caused by tumors, especially on the skin, which may cause psychological effects in people with tumors. Vascular tumors can bleed, which in some cases can be substantial, leading to anemia.
Cause
PTEN hamartoma syndrome
PTEN hamartoma syndrome consists of four distinct hamartomatous disorders characterized by genetic mutations in the PTEN gene; Cowden syndrome, Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome and Proteus-like syndrome. Although they all have different clinical features, the formation of hamartomas is present in all four syndromes. PTEN is a tumor suppressor gene involved in cellular signaling. The absent or dysfunctional PTEN protein allows cells to overproduce, causing hamartoma.
Cowden syndrome is an autosomal dominant genetic disorder characterized by several benign hamartomas (trichilemmomas and papillomatous papillomatous mucocutaneous) as well as predisposing to various organ cancers including breast and thyroid. Bannayan-Riley-Ruvalcaba syndrome is a congenital aberration characterized by hamartomatous intestinal polyposis, macrocephaly, lipomatosis, haemangiomatosis and glans penis macules. The proteus syndrome is characterized by nevi, asymmetric overgrowth of various body parts, dysregulated adipose tissue, cystadenomas, adenomas, vascular malformations.
Familial adenomatous polyposis
Familial adenomatous polyposis (FAP) is a family cancer syndrome caused by mutations in the APC gene. In this disorder adenomatous polyps present in the colon always develop into colon cancer. The APC gene is a tumor suppressor and its products are involved in many cellular processes. APC gene inactivation leads to a buildup of a protein called -cathenine, which activates two transcription factors; T-cell factor (TCF) and lymphoid enhancer factor (LEF). This leads to increased regulation of genes involved in cell proliferation, differentiation, migration and apoptosis (programmed cell death), leading to the growth of benign tumors.
Tuberous sclerosis complex
The tuberous sclerosis complex (TSC) is a dominant autosomal genetic disorder caused by mutations in genTSC1 and TSC2, which produce hamartin and tuberin proteins, respectively. This disorder presents with many benign hamartomatous tumors including angiofibroma, renal angiomyolipomas, pulmonary lymphangiomiomatosis. Tuberin and hamartin inhibit mTOR proteins in normal cellular physiology and inactivation of TSC tumor suppressors results in increased mTOR activity. This leads to gene activation and protein production that increase cell growth.
Von Hippel-Lindau's disease
Von Hippel-Lindau disease is a predominantly dominant cancer syndrome that increases the risk of many tumors including benign hemangioblastoma and malignant pheochromocytomas, renal cell carcinoma, pancreatic endocrine tumors and endolymphatic sac tumors. This is due to a genetic mutation in the tumor suppressor gene Von Hippel-Lindau. VHL proteins (pVHL) are involved in cellular signaling in oxygen-deprived cells (hypoxia). One role of pVHL is to cause cellular degradation of other proteins, HIF1 ?. Dysfunctional PVHL leads to accumulation of HIF1, which in turn activates the production of several genes involved in cell growth and blood vessel production (VEGF, PDGF ?, TGF? And erythropoietin).
Mechanism
Benign vs. malignant
One of the most important factors in classifying tumors as benign or malignant is its invasive potential. If the tumor does not have the ability to invade adjacent tissue or spread to distant sites with metastasis then it is benign, while invasive or malignant metastatic tumors. For this reason, benign tumors are not classified as cancer. Benign tumors will grow in the contained area usually packed in a fibrous connective tissue capsule. The growth rates of benign and malignant tumors are also different; Benign tumors generally grow more slowly than malignant tumors. Although benign tumors pose a lower health risk than malignant tumors, they can both be life-threatening in certain situations. There are many common characteristics that apply to benign or malignant tumors, but sometimes one type may exhibit other characteristics. For example, benign tumors are largely differentiated well and malignant tumors are often undifferentiated. However, undifferentiated benign tumors and differentiated malignant tumors may occur. Although benign tumors generally grow slowly, cases of rapidly growing benign tumors have also been documented. Some malignant tumors mostly do not metastasize as in the case of basal cell carcinoma. CT and chest radiography can be a useful diagnostic test in visualizing benign tumors and differentiating them from malignant tumors. The smaller the tumor on radiography, the more likely it is benign because 80% of pulmonary nodules are less than 2 cm in diameter. Most benign nodules are a smooth radiopaque density with clear margins but these are not the exclusive signs of benign tumors.
Carcinogenesis multistage
Tumors are formed by carcinogenesis, a process in which cell changes lead to cancer formation. Multistage carcinogenesis involves sequential genetic or epigenetic changes to cell DNA, where each step produces a more advanced tumor. Often broken down into three stages; initiation, promotion and development, and several mutations can occur at every stage. Initiation is where the first genetic mutation occurs in the cell. Promotion is the clonal expansion (repetitive division) of this transformed cell into a visible tumor that is usually benign. After promotion, development may occur where more genetic mutations are obtained in the tumor cell sub-population. Progressive turns a benign tumor into a malignant tumor. A prominent and well-studied example of this phenomenon is the tubular adenoma, a common type of colon polyp that is an important precursor to colon cancer. Cells in tubular adenomas, like most tumors that often develop into cancer, exhibit certain abnormalities of cell maturation and appearance that are collectively known as dysplasia. This cellular disorder is not seen in benign tumors that are rarely or never turn cancerous, but are seen in other pre-cancerous tissue abnormalities that do not form discrete masses, such as pre-cancerous uterine cervical lesions. Some authorities prefer to refer to dysplastic tumors as "pre-malignant", and reserve the term "benign" for tumors that rarely or never cause cancer.
Diagnosis
Treatment
Some benign tumors do not require treatment; others may be removed if they cause problems such as seizures, discomfort or cosmetic problems. Surgery is usually the most effective approach and is used to treat most benign tumors. In some cases, other treatments may be useful. Rectal adenoma can be treated with sclerotherapy, a treatment in which chemicals are used to shrink the blood vessels to cut off the blood supply. Most benign tumors do not respond to chemotherapy or radiation therapy, although there are exceptions; Benign interganial tumors are sometimes treated with radiation therapy and chemotherapy under certain circumstances. Radiation can also be used to treat hemangioma in the rectum. Benign skin tumors are usually resected surgically but other treatments such as cryotherapy, curettage, electrodesiccation, laser therapy, dermabrasion, chemical peels and topical medications are used.
References
Source of the article : Wikipedia
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