Cancer, also known as a malignant tumor, is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body.[1][2] Not all tumors are cancerous; benign tumors do not spread to other parts of the body.[2] Possible signs and symptoms include: a new lump, abnormal bleeding, a prolonged cough, unexplained weight loss, and a change in bowel movements, among others.[3] While these symptoms may indicate cancer they may also occur due to other issues.[3] There are over 100 different known cancers that affect humans.[2]
’’’癌症’’’又名為{{link-en|惡性|malignant}}[[腫瘤]]，指的是細胞不正常{{link-en|增生|cell growth}}，且這些增生的細胞可能[[遠端轉移|侵犯]]身體的其他部分[1][2]。不是所有的腫瘤都會癌化，有些細胞增生不會侵犯身體其他部分，稱為[[良性腫瘤]][2]。癌症常見的[[醫學徵象|徵象]]與[[症狀]]包括新發生的腫塊、異常的[[出血]]、慢性[[咳嗽]]、無法解釋的體重減輕、以及[[排便|腸胃蠕動]]的改變等等[3]，但其他疾病也可能會出現這些症狀，因此發現這些症狀並不一定表示得了癌症[3]。在人類身上，目前已知的癌症超過一百種[2]。
<!--Cause and Diagnosis -->
Tobacco use is the cause of about 22% of cancer deaths.[1] Another 10% is due to obesity, a poor diet, lack of physical activity, and drinking alcohol.[1] Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants.[4] In the developing world nearly 20% of cancers are due to infections such as hepatitis B, hepatitis C, and human papillomavirus.[1] These factors act, at least partly, by changing the genes of a cell.[5]Typically many such genetic changes are required before cancer develops.[5] Approximately 5–10% of cancers are due to genetic defects inherited from a persons parents.[6] Cancer can be detected by certain signs and symptoms or screening tests.[1] It is than typically further investigated by medical imaging and confirmed by biopsy.[7]
<!-- 成因與診斷 -->
因吸[[菸]]而罹癌者佔了癌症死者中的22%[1]，[[肥胖症|肥胖]]、飲食不佳、運動不足、飲[[酒]]則共佔了10%[1]。其他可能造成癌症的因素還包括某些[[感染]]、暴露於[[游離輻射]]、以及環境汙染因子[4]。在[[發展中國家]]約有20%的癌症是由於感染症（如[[B型肝炎]]、[[C型肝炎]]、以及[[人類乳突病毒]]等）造成[1]。致癌因子通常是透過改變細胞中的[[基因|遺傳物質]]運作[5]，通常許多這類遺傳物質的變化是癌症產生所必要的[5]。約5到10%的癌症是由於遺傳自雙親的基因異常[6]。癌症可以由症狀和徵候或透過{{link-en|癌症篩檢|Cancer screening|篩檢}}的方式發現[1]，然後再以[[醫學影像|影像]]檢查和[[活體組織切片|切片]]檢查來確診[7]。
<!-- Prevention and Treatment -->
Many cancers can be prevented by not smoking, eating more vegetables, fruits and whole grains, eating less meat and refined carbohydrates, maintaining a healthy weight, exercising, minimizing sunlight exposure, and being vaccinated against certain infectious diseases.[4][8] Early detection through screening is useful for cervical and colorectal cancer.[9] The benefits of screening in breast cancer are controversial.[10][9] Cancer is often treated with some combination of chemotherapy, radiation therapy, and surgery. Pain and symptom management are an important part of care. Palliative care is particularly important in those with advanced disease.[1] The chance of survival depends on the type of cancer and extent of disease at the start of treatment.[11] In children the five year survival in the developed world is on average of 80%.[12] For cancer in the United States the average five year survival is 66%.[13]
<!-- 預防與治療 -->
許多癌症都可以預防，預防的方式包括[[戒烟]]、多吃蔬菜水果及全穀類食品、減少[[肉類食物]]與精製[[醣類|碳水化合物]]的攝取、維持健康體重、多運動、減少陽光曝曬、以及施打疫苗預防感染症等等[4][8]。透過篩檢早期發現，對於部分的癌症（包括[[大腸癌|大腸直腸癌]]和[[子宮頸癌]]等）有用[9]，但[[乳癌]]篩檢的價值則有爭議性[9][10]。對癌症的治療方式通常結合[[化學療法]]、[[放射療法]]以及[[外科手術|手術]]等。疼痛控制與症狀控制是癌症治療中重要的一環，而[[安寧緩和醫療]]對於疾病已進展到較晚期的病人來說相當重要[1]。癌症病人的存活率端看癌症的種類與開始治療時的疾病狀況[11]。在[[已開發國家]]兒童癌症病人的五年存活率平均高達80%[12]，在[[美國]]的成年癌症病人的平均五年存活率則有66%[13]。
<!-- Epidemiology -->
In 2012 cancer occurred in about 14.1 million people.[11] It caused about 8.2 million deaths or 14.6% of all human deaths.[11][14] The most common types of cancer in males are lung cancer, prostate cancer, colorectal cancer and stomach cancer. In females the most common types are breast cancer, colorectal cancer, and lung cancer, and cervical cancer.[11] In children acute lymphoblastic leukaemia and brain tumors are most common except in Africa where non-Hodgkin lymphoma occurs more often.[12] In 2012 about 165,000 children less than 15 years of age were diagnosed with cancer. The risk of cancer increases significantly with age and many cancers occur more commonly in developed countries.[11] Rates are increasing as more people live to an old age and as lifestyle changes occur in the developing world.[15]
<!-- 流行病學 -->
在2012年，大約有1,410萬人得到癌症[11]，並且造成820萬人身亡（相當於全年總死亡人數的14.6%）[11][14]。男性身上最常見的癌症包括[[肺癌]]、[[前列腺癌|前列腺癌（攝護腺癌）]]、[[大腸直腸癌]]、以及[[胃癌]]；在女性身上最常見的則是[[乳癌]][11]、大腸直腸癌、肺癌和[[子宮頸癌]]。兒童以[[急性淋巴性白血病]]和[[腦瘤]]最常見，不過非洲除外，[[非何金氏淋巴瘤]]在那裡更常見[12]。2012年，大約16.5萬個15歲以下的兒童被診斷出罹患癌症。罹癌的風險會隨著年齡的增長而升高，同時有數種癌症在[[已開發國家]]較常見[11]。隨著人類越來越長壽及開發中國家生活習慣的改變，全球的罹癌率整體而言在上升中[15]。