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Myelolipoma (''myelo-'', from the ancient greek ''μυελός'', marrow; ''lipo'', meaning ''of, or pertaining to, fat''; ''-oma'', meaning ''tumor or mass'') is a benign tumor-like lesion composed of mature adipose (fat) tissue and haematopoietic (blood-forming) elements in various proportions. Myelolipomas can present in the adrenal gland, or outside of the gland. ==Causes== Although several hypotheses have been proposed as to the cause of myelolipoma, the causative process is still not clearly understood. Recent experimental evidence suggests that both the myeloid and lipomatous elements have a monoclonal origin, which strongly supports the hypothesis that myelolipomas are neoplastic lesions.〔 Older theories proposing a non-neoplastic origin include the following: * Adrenal cortical cells, or other cells within the stroma of the adrenal cortex that are able to differentiate, may reversibly change into fat or blood-forming cells. This might occur because of the actions of adrenal cortex hormones, or of hormones released by the pituitary gland that act on the adrenal glands, such as adrenocorticotropic hormone (ACTH). * The blood-forming cells may arise by differentiation of cells within the capillaries of the adrenal gland.〔Ramchandani, P. 〕 * Myelolipoma simply represents a site of normal blood formation outside the bone marrow.〔 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「myelolipoma」の詳細全文を読む スポンサード リンク
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