We present a case of a 9-year-old girl with no significant medical history who developed acute onset of shortness of breath and upper chest pain during cheerleading practice. Laboratory results and physical examination were unremarkable. Chest radiograph and chest CT showed an expansile lytic aggressive-appearing mass within the left sixth rib. Subsequent F-FDG PET/CT showed a left sixth rib lesion that was not hypermetabolic and appeared benign. Biopsy yielded a diagnosis of enchondroma, a benign intramedullary tumor that accounts for 24% of all bone tumors in children as well as adolescents.