13-year-old male with a sacral mass being evaluated for malignancy and metastasis.

Intense FDG uptake is seen in the right hilar and mediastinal area suspicious for lymph nodes. Focally intense FDG uptake is seen in the region of the upper thoracic spine, lower thoracic spine, left iliac wing and right sacroiliac joint. Mildly intense FDG uptake is also noted in the area left of the bladder. Additionally, there is intense FDG uptake in the known sacral mass.

Intense metabolic activity in the sacral mass is suspicious for malignancy. Abnormal FDG-PET study with hypermetabolic lesions in the regions of the right hilum and mediastinum suspicious for lymph nodes; thoracic spine and pelvis as described above may represent areas of metastasis.

In the context of the sacral mass biopsy on the following day showing numerous non-caseating granulomas with positive acid fast stains consistent with Mycobacterium tuberculosis, the lesions described could represent hypermetabolism due to an infectious/inflammatory process.