Osteoblastoma is a metabolically active benign bone tumor on 18F-FDG PET imaging.

We describe a case of a 9-y-old girl who on (18)F-FDG PET imaging was found to have a highly metabolically active sacral tumor with an average standarized uptake value of 6.2. The tumor was proven to be osteoblastoma by pathologic examination. Osteoblastoma is a relatively rare benign primary bone tumor and occurs predominantly in patients younger than 20 y. The most common area of involvement is the spine. Osteoblastoma has been reported to be metabolically active on (18)F-FDG PET imaging, with an average standarized uptake value of 3.2, which renders (18)F-FDG PET imaging unable to differentiate benign from malignant primary bone tumors. To our knowledge, only 5 cases of osteoblastoma evaluated by (18)F-FDG PET imaging have been reported in the literature; all were metabolically active on (18)F-FDG PET imaging. The objective of this case report is to show that a metabolically active primary bone tumor on (18)F-FDG PET imaging might be benign and not necessarily malignant.