Dr. Leif Ellisen is associate professor of medicine at Harvard Medical School, and associate physician at Massachusetts General Hospital.

Dr. Ellisen received his BA in biology from Harvard College, and his MD and PhD in cancer biology from Stanford University. His internal medicine internship and residency were completed at Brigham and Women's Hospital. Dr. Ellisen was a clinical fellow in hematology and oncology at the Dana-Farber Cancer Institute in Boston, and completed postdoctoral training in cancer genetics at Massachusetts General Hospital.

Dr. Ellisen is an editorial board member of the Journal of Clinical Oncology, and the Journal of Clinical Investigation.