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A lesion is any abnormality in the tissue of an organism (in layman's terms, "damage"), usually caused by disease or trauma. ''Lesion'' is derived from the Latin word ''laesio'' meaning ''injury''. ==Types == Because the definition of a lesion is so broad, the varieties of lesions are virtually endless. Lesions can occur anywhere in the body that consists of soft tissue or osseous matter, though most frequently found in the mouth, skin, and the brain, or anywhere where a tumour may occur. They are subsequently classified by their features. If a lesion is caused by a tumor it will be classified as ''malignant'' or ''benign''. Lesions may be classified by the shape they form, as is the case with many ulcers, which can have a bullseye or 'target' appearance. Their size may be specified as ''gross'' or ''histologic'' depending on whether they are visible to the unaided eye or require a microscope to see. An additional classification that is sometimes used is based on whether or not a lesion occupies space. A ''space-occupying lesion'', as the name suggests, has a recognizable volume and may impinge on nearby structures, whereas a ''non space-occupying lesion'' is simply a hole in the tissue, e.g. a small area of the brain that has turned to fluid following a stroke. Some lesions have specialized names, such as Ghon lesions in the lungs of tuberculosis victims. The characteristic skin lesions of a varicella zoster virus (VZV) infection are called ''chickenpox''. Lesions of the teeth are usually called dental caries. Another type of lesion is excitotoxic lesions that can be caused by excitatory amino acid like kainic acid that kills neurons through over-stimulation. ''Sham lesion'' is the name given to a control procedure during a lesion experiment. In a sham lesion, an animal may be placed in a stereotaxic apparatus and electrodes inserted as in the experimental condition, but no current is passed, and therefore damage to the tissue should be minimal. Finally, lesions are often classified by their location. For example, a "skin lesion" or a "brain lesion". 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「Lesion」の詳細全文を読む スポンサード リンク
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