Vertebral Body Osteonecrosis Mimicking Malignant Disease on 18F-FDG PET

We report a case of vertebral osteonecrosis after chemotherapy in a 24-year-old man with non-Hodgkin lymphoma, with transient avidity on 18F-FDG PET initially misinterpreted as recurrent extranodal disease. The patient demonstrated a partial metabolic response on midtreatment restaging PET; however, posttreatment PET showed an increase in uptake in T4 and T5 vertebrae, interpreted as recurrent vertebral disease. Repeat PET performed 9 days later showed resolution of thoracic vertebral uptake without interval treatment. On follow-up PET study, thoracic vertebrae demonstrated photopenia with sclerosis on CT, concerning for osteonecrosis. MRI features were concordant with this diagnosis.