Metastasis wani wakili ne mai yaduwa daga wuri na farko ko na farko zuwa wani wuri daban ko na biyu a cikin jikin mai gida; yawanci ana amfani da kalmar lokacin da ake magana akan metastasis ta hanyar ciwon daji. Sabbin wuraren cututtukan cututtuka, to, sune metastases ( mets ). Gabaɗaya an bambanta shi daga mamayewar kansa, wanda shine haɓaka kai tsaye da shigar da ƙwayoyin cutar kansa zuwa kyallen maƙwabta. Ciwon daji yana faruwa ne bayan sel sun canza ta hanyar kwayoyin halitta don yaduwa cikin sauri kuma har abada. Wannan yaduwar rashin kulawa ta hanyar mitosis yana haifar da ƙwayar cuta ta farko. Kwayoyin da ke haifar da ƙari daga ƙarshe suna yin metaplasia, sannan dysplasia sannan anaplasia, wanda ke haifar da mummunan phenotype. Wannan malignancy yana ba da damar mamayewa a cikin wurare dabam dabam, sannan kuma mamayewa zuwa wuri na biyu don tumorigenesis . Wasu ƙwayoyin cutar kansa da aka sani da ƙwayoyin tumor masu yaduwa suna samun damar shiga bangon lymphatic ko tasoshin jini, bayan haka za su iya yaduwa ta cikin jini zuwa wasu shafuka da kyallen takarda a cikin jiki. An san wannan tsari (bi da bi) azaman yaduwar lymphatic ko hematogenous .