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A sebaceous cyst is a general term that is used to refer to either:〔(【引用サイトリンク】title=Epidermoid and pilar cysts (previously known as sebaceous cysts) )〕 * Epidermoid cysts (also termed ''epidermal cysts'', ''infundibular cyst''), or * Pilar cysts (also termed ''trichelemmal cysts'', ''isthmus-catagen cysts''). However, the above types of cyst contain keratin, not sebum, and neither originates from sebaceous glands (epidermoid cysts originate in the epidermis and pilar cysts originate from hair follicles). Therefore technically speaking they are not sebaceous cysts.〔(【引用サイトリンク】title=Epidermoid and Pilar Cysts (Sebaceous Cysts) - Patient UK )〕 "True" sebaceous cysts (i.e. cysts which originate from sebaceous glands and which contain sebum) are relatively rare and are known as steatocystomas or, if multiple, as steatocystoma multiplex. It has therefore been suggested that the term ''sebaceous cyst'', when used to refer to epidermoid cysts and pilar cysts, should be avoided since this is misleading. In practice, however, the terms are still often used interchangeably. ==Signs and symptoms== The scalp, ears, back, face, and upper arm, are common sites for sebaceous cysts, though they may occur anywhere on the body except the palms of the hands and soles of the feet. In males a common place for them to develop is the scrotum and chest. They are more common in hairier areas, where in cases of long duration they could result in hair loss on the skin surface immediately above the cyst. They are smooth to the touch, vary in size, and are generally round in shape. They are generally mobile masses that can consist of: * Fibrous tissues and fluids, * A fatty (keratinous) substance that resembles cottage cheese, in which case the cyst may be called "keratin cyst". This material has a characteristic "cheesy" or foot odor smell, * A somewhat viscous, serosanguineous fluid (containing purulent and bloody material). The nature of the contents of a sebaceous cyst, and of its surrounding capsule, will be determined by whether the cyst has ever been infected. With surgery, a cyst can usually be excised in its entirety. Poor surgical technique or previous infection leading to scarring and tethering of the cyst to the surrounding tissue may lead to rupture during excision and removal. A completely removed cyst will not recur, though if the patient has a predisposition to cyst formation, further cysts may develop in the same general area. 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「sebaceous cyst」の詳細全文を読む スポンサード リンク
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