良性腫瘤指腫瘤細胞未發生轉移與侵入周遭組織的情形，反之則稱為惡性腫瘤，多數會影響生理功能的腫瘤都是惡性腫瘤。
选择某些生活方式会增加患癌风险。抽烟、女性每天饮酒超过一杯、男性每天饮酒两杯以上、过度暴露在阳光下或经常晒伤起疱、肥胖和不安全的性行为都可能导致癌症。
In sporadic cancers, deficiencies in DNA repair are sometimes caused by a mutation within a DNA mend gene but are way more usually because of epigenetic alterations that reduce or silence expression of DNA repair genes. This is certainly indicated within the figure in the 3rd degree. Quite a few research of significant metallic-induced carcinogenesis present that these types of weighty metals bring about a discount in expression of DNA repair service enzymes, some by means of epigenetic mechanisms.
某些癌症的成長會受某些荷爾蒙的增加或減少而抑制。對荷爾蒙敏感的腫瘤常見的例子有乳癌和前列腺癌，減低或增加體內雌激素或雄激素往往可用來做為補充治療的一種。
早期發現對於癌症治療的成功至關重要。癥狀可能因癌症類型和受影響的器官而異，但常見指標包括： 不明原因的體重減輕
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An extra mutation may perhaps bring 癌症 about the loss of a tumor suppressor gene, disrupting the apoptosis signaling pathway and immortalizing the cell.
不受限制的生長（不死，由於有大量端粒酶，細胞不受到細胞凋亡機制的調控）
An additional mutation inside the signaling machinery with the mobile may possibly deliver mistake-resulting in indicators to nearby cells.
化学致癌物，例如石棉、烟草烟雾成分、酒精、黄曲霉毒素（一种食品污染物）、 砷（一种饮水污染物）、烷化剂、酰化剂、亚硝胺类、芳香胺、环氧化物等；巴豆油、 激素、酚类等物品，会增加致癌物质的效应。
癌細胞擴散至距離原始腫瘤遙遠的器官及組織。此時癌細胞流竄於全身，必需借助循環全身的化學治療藥物治療。安寧照護將是治療選項之一。
Signs or symptoms of cancer metastasis depend upon The placement from the tumor. When cancer starts, it creates no signs or symptoms. Symptoms and indicators appear because the mass grows or ulcerates.
The conclusions that outcome depend on most cancers's sort and placement. Couple of indications are particular. Quite a few frequently take place in individuals who produce other disorders. Most cancers can be hard to diagnose and might be viewed as a "terrific imitator".[33]