A major issue associated to the use of embryonic stem cells in regenerative medicine is their tendency to induce tumour formation in the transplant receiver due to their undifferentiated state. This does not seem to happen when adult cells are used, however. In a recent letter published in JAMA (309; 1458-1459, 2013), the authors found that the use of mesenchymal cells (a type of adult stem cell) in the treatment of myocardial infarction, was not associated to the formation of neoplasia.