Transformation of induced pluripotent stem cells into tumor cells could be a consequence of oncogenic properties of the reprogramming coctail (use of c_MYC), or insertional mutagenesis induced by the reprogramming with integrating retroviral or lentiviral vectors which disrupts endogenous genes. Recently, clinical trial that investigated potential of autologous induced pluripotent stem cells-retinal pigment epithelial cells for the treatment of advanced neovascular age-related macular degeneration has been stopped. Although transplantation of induced pluripotent sten cell-retinal pigmen epithelial cells in the first enrolled patient was well tolerated after one year follow-up, study was stopped when it moved on to a possible second patient. Since induced pluripotent stem cell, derived from second patient contained mutation, they did not pass a genomic validation step and the team lead by Takahashi decided to at least remporarily suspend the trial. However, what remains unclear at this time and what should be explored is wether the mutation in the second patient’s induced pluripotent stem cell was pre-existing in the patient’s fibroblasts or it occured during the reprogramming process itself.