學這些英文用法：TED-Ed,轉移,癌細胞,癌症,腫瘤,擴散,免疫,理論,部位,血管,身體,肝臟,土壤,種 ...Theonsetofcancerusuallybeginsasasolitarytumor癌症通常是從身體裡一個特定部位的inaspecificareaofthebody.單一腫瘤開始Ifthetumorisnotremoved,如果腫瘤沒有被切除cancerhastheabilitytospreadtonearbyorgans,癌症就有辦法傳播到附近的器官aswellasplacesfarawayfromtheorigin,suchasthebrain.或是距離發源地較遠的地方，例如腦部Sohowdoescancermovetonewareas,那麼癌症是如何移動到新的區域的呢？andwhyaresomeorgansmorelikelytogetinfectedthanothers?又是為什麼有些器官比其他器官更易受到感染呢？Theprocessofcancerspreadingacrossthebodyisknownasmetastasis.癌症在身體裡擴散的形式叫做「轉移」Itbeginswhencancercellsfromaninitialtumorinvadenearbynormaltissue.這會從癌細胞由原本的腫瘤入侵附近的一般組織時開始Asthecellsproliferate,當癌細胞開始擴散theyspreadviaoneofthethreecommonroutesofmetastasis:它們會透過三種常見的轉移路徑進行擴散：transcoelomic,lymphatic,orhematogenousspread.移植性轉移、淋巴性轉移與血行性轉移Intranscoelomicspread,malignantcellspenetratethecoveringsurfaces在移植性轉移中，惡性細胞會穿透身體裡ofcavitiesinourbody.覆蓋體腔的防護表層Thesesurfacesareknownasperitoneum這些表層就是所謂的腹膜(腹腔中的一層黏膜)andserveaswallstosegmentthebodycavity.用以區隔身體裡的腔室Malignantcellsinovariancancer,forexample,舉例來說，卵巢癌的惡性細胞spreadthroughperitoneum,whichconnectstheovarytotheliver,透過連接卵巢與肝臟的腹膜擴散resultinginmetastasisontheliversurface.導致癌細胞轉移到肝臟表面Next,cancerouscellsinvadebloodvesselswhentheyundergohematogenousspread.接下來，癌細胞在血行性轉移就會侵入血管Astherearebloodvesselsalmosteverywhereinthebody,正因為血管幾乎遍及全身malignantcellsutilizethistoreachmoredistantpartsofthebody.惡性細胞便藉此移動到更遠的身體部位Finally,lymphaticspreadoccurswhenthecancerinvadesthelymphnodes,最後，當癌症入侵到淋巴結時就會發生淋巴性轉移andtravelstootherpartsofthebodyviathelymphaticsystem.並且透過淋巴系統轉移到身體其他部位Asthissystemdrainsmanypartsofthebody,正因此系統流遍了身體的許多部位italsoprovidesalargenetworkforthecancer.它也就提供了癌症一個很大的流通網路Inaddition,thelymphaticvesselsemptyintothebloodcirculation,此外，當淋巴管注入血液循環系統後allowingthemalignantcellstoundergohematogenousspread.就使得惡性細胞得以進行血行性擴散Onceatanewsite,thecellsonceagainundergoproliferation,一旦細胞開始在新的地點再次增值andformsmalltumorsknownasmicrometastases.並形成小腫瘤時，就是所謂的轉移Thesesmalltumorsthengrowintofull-fledgedtumors,這些小腫瘤並長成成熟的腫瘤andcompletethemetastaticprocess.進而完成轉移的過程