Mackall completed an Internal Medicine and Pediatrics Residency at Cleveland Clinic Akron General and Children’s Hospital of Akron in 1988.[3] In 1989, Mackall joined the National Cancer Institute as a fellow in Pediatric Oncology, where she began to focus on immunotherapy for cancer.[4][5] She remained at National Institutes of Health until 2016, eventually serving as the Chief of the Pediatric Oncology Branch.[6] She moved to the Stanford University School of Medicine in 2016.[7] She is Board Certified in Internal Medicine, Pediatrics, and Pediatric Hematology/Oncology.[8][9]