Do benign tumors arise by transformation?

Yes. All tumors arise from normal pre existing cells that have undergone some form of transformation. Several oncogenes are turned on to present the benign as well as malignant lesion with immortality. In the case of the malignant tumor additional changes allow for matrix metalloproteinase to be produced to dissolve walls of blood vessels for metastasis and convert e-cadherin to small e cad.