A patient given repeated injections of fetal neural stem cells to treat a rare genetic disease developed tumors in his brain and spinal cord that arose from the transplanted cells, Israeli researchers reported (Amariglio N et al. PLoS Med. 2009;6:e1000029).
The patient, an Israeli boy who has ataxia telangiectasia, a disease that is usually fatal in the second or third decade and causes degeneration of certain brain regions and impaired immunity, received the fetal stem cells at a Moscow clinic when he was 9, 10, and 12 years old. Later, at a medical center in Israel (that had no role in the stem cell therapy), physicians discovered the boy had tumors in his brain and spinal cord. Tests of the tumor tissue revealed that the growth was derived from fetal cells, although the boy's underlying impaired immunity might have facilitated tumor growth.
Stephenson J. Tumors From Stem Cells. JAMA. 2009;301(11):1118. doi:10.1001/jama.2009.356