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A lipoma is a benign tumor composed of adipose tissue (body fat). It is the most common benign form of soft tissue tumor. Lipomas are soft to the touch, usually movable, and are generally painless. Many lipomas are small (under one centimeter diameter) but can enlarge to sizes greater than six centimeters. Lipomas are commonly found in adults from 40 to 60 years of age, but can also be found in younger adults and children. Some sources claim that malignant transformation can occur,〔('Obesity Gene' Causes Cancer of Fat Tissue, Schepens Scientists Find ) Schepens Eye Research Institute (Harvard Medical School affiliate). April 26, 2000〕 while others say this has yet to be convincingly documented.〔 ==Types== There are many subtypes of lipomas: * Adenolipomas are lipomas associated with eccrine sweat glands. * Angiolipoleiomyomas are acquired, solitary, asymptomatic acral nodules, characterized histologically by well-circumscribed subcutaneous tumors composed of smooth muscle cells, blood vessels, connective tissue, and fat.〔 * Angiolipomas are painful subcutaneous nodules having all other features of a typical lipoma.〔 * Cerebellar pontine angle and internal auditory canal lipomas * Chondroid lipomas are deep-seated, firm, yellow tumors that characteristically occur on the legs of women.〔 * Corpus callosum lipoma is a rare congenital brain condition that may or may not present with symptoms. This occurs in the corpus callosum, also known as the colossal commissure, which is a wide, flat bundle of neural fibers beneath the cortex in the human brain. * Hibernomas are lipomas of brown fat. * Intradermal spindle cell lipomas are distinct in that they most commonly affect women and have a wide distribution, occurring with relatively equal frequency on the head and neck, trunk, and upper and lower extremities.〔〔 * Neural fibrolipomas are overgrowths of fibro-fatty tissue along a nerve trunk, which often leads to nerve compression.〔 * Pleomorphic lipomas, like spindle-cell lipomas, occur for the most part on the backs and necks of elderly men and are characterized by floret giant cells with overlapping nuclei.〔 * Spindle-cell lipomas are asymptomatic, slow-growing subcutaneous tumors that have a predilection for the posterior back, neck, and shoulders of older men.〔 * Superficial subcutaneous lipomas, the most common type of lipoma, lie just below the surface of the skin.〔 Most occur on the trunk, thigh, and forearm, although they may be found anywhere in the body where fat is located. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lipoma」の詳細全文を読む スポンサード リンク
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