Different tumor types can have different oncogenes activated. Oncogenes are genes that are active in development, but are turned off after birth. Something damages the promoter (switch) and the gene turns on. There are also a few tumor supressor genes that are normally on after birth that keep the oncogenes turned off and if damaged, can cause tumors (ex: retinoblastoma).
That is why there will very likely be no one "cure" for cancer.