癌症是以异常细胞生长为特征的众多疾病的统称，这些异常细胞会失控地分裂，并能浸润和毁坏正常身体组织。癌症通常可以扩散到全身各处。
Genetic improvements can occur at different levels and by different mechanisms. The acquire or lack of a whole chromosome can happen by errors in mitosis. Much more common are mutations, which can be variations from the nucleotide sequence of genomic DNA.
Disruption of an individual gene can also outcome from integration of genomic product from a DNA virus or retrovirus, bringing about the expression of viral oncogenes while in the afflicted mobile and its descendants.
主要原理是使用高專一性的單株抗體直接結合到腫瘤細胞特有的蛋白質或是細胞激素，影響腫瘤細胞的生長、引起免疫系統反應或是其他功能。已經發展的藥物有針對乳癌的曲妥珠单抗和針對白血病的吉妥单抗在臨床使用。
DNA fix inhibition is proposed to generally be a predominant mechanism in major metal-induced carcinogenicity. Also, Recurrent epigenetic alterations in the DNA sequences code for smaller RNAs known as microRNAs (or miRNAs). miRNAs will not code for proteins, but can "target" protein-coding genes and minimize their expression.
全身性的症狀：體重減輕、食欲不振、惡病體質、大量出汗（夜間盜汗）、貧血
The influenced genes are divided into 癌症 two broad groups. Oncogenes are genes that market cell advancement and copy. Tumor suppressor genes are genes that inhibit mobile division and survival. Malignant transformation can take place in the formation of novel oncogenes, the inappropriate in excess of-expression of usual oncogenes, or via the below-expression or disabling of tumor suppressor genes.
减少接触室外和室内空气污染，包括氡（一种由铀的自然衰变产生的放射性气体，可能在建筑物中，住宅、学校和工作场所积累）。
第三步——发育不良，除了增殖过度外，粉色细胞的后代在形状和方向上也出现 异常；该组织被称为发育不良。再一段时间过后，一种罕见的改变细胞行为的突变 发生了（紫色）。
The incidence of lung cancer is extremely correlated with using tobacco. Exposure to specific substances are associated with specific forms of most cancers. These substances are called carcinogens.
Significant-scale mutations involve the deletion or acquire of a percentage of a chromosome. Genomic amplification takes place any time a mobile gains copies (normally 20 or more) of a little chromosomal locus, usually made up of one or more oncogenes and adjacent genetic materials. Translocation occurs when two different chromosomal locations come to be abnormally fused, typically at a characteristic location.
多數癌症是自發性的（英语：sporadic），但是有些癌症還是與遺傳有關，通常遺傳到缺陷的腫瘤抑制基因時會有較顯著的影響和症狀。舉例而言：
戒烟。如果您抽烟，请戒烟。如果您不吸烟，请勿开始抽烟。抽烟与多种癌症有关，而不仅仅是肺癌。立即停止吸烟会降低您将来患癌症的风险。
烟草使用、酒精消费、不健康饮食、缺乏身体活动和空气污染是癌症（以及其他非传染性疾病）的危险因素。