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Neoplasm (from Ancient Greek νέος- ''neo'' "new" and πλάσμα ''plasma'' "formation, creation") is an abnormal growth of tissue, and when also forming a mass is commonly referred to as a tumor or tumour. This abnormal growth (neoplasia) usually but not always forms a mass. The World Health Organization (WHO) classifies neoplasms into four main groups: benign neoplasms, in situ neoplasms, malignant neoplasms, and neoplasms of uncertain or unknown behavior.〔(【引用サイトリンク】url=http://apps.who.int/classifications/icd10/browse/2010/en )〕 Malignant neoplasms are also simply known as cancers. Prior to the abnormal growth of tissue, as neoplasia, cells often undergo an abnormal pattern of growth, such as metaplasia or dysplasia. However, metaplasia or dysplasia do not always progress to neoplasia. ==Types== A neoplasm can be benign, potentially malignant (pre-cancer), or malignant (cancer).〔(【引用サイトリンク】title=Cancer - Activity 1 - Glossary, page 4 of 5 )〕 * Benign tumors include uterine fibroids and melanocytic nevi (skin moles). They are circumscribed and localized and do not transform into cancer.〔 * Potentially-malignant neoplasms include carcinoma in situ. They are localised, do not invade and destroy but in time, may transform into a cancer. * Malignant neoplasms are commonly called cancer. They invade and destroy the surrounding tissue, may form metastases and untreated or unresponsive to treatment, will prove fatal. * Secondary neoplasm refers to any of a class of cancerous tumor that is either a metastatic offshoot of a primary tumor, or an apparently unrelated tumor that increases in frequency following certain cancer treatments such as chemotherapy or radiotherapy. * Rarely there can be a metastatic neoplasm with no known site of the primary cancer and this is classed as a cancer of unknown primary origin 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「neoplasm」の詳細全文を読む スポンサード リンク
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