Calcified Substernal Goiter Seen on Bone Scan

A Tc-99m MDP scan of a 59-year-old man diagnosed with prostate carcinoma was obtained to rule out metastatic bone disease, which showed a focal intense uptake within the upper sternal region. Subsequent SPECT scan of the chest showed that this scintigraphic abnormality was located in the upper mediastinum and did not involve the sternum. Chest radiographs were obtained and showed a mass with a subtle eggshell calcification in the retrosternal superior mediastinum. Review of previous bone scans and clinical and laboratory data revealed the diagnosis of substernal thyroid with dystrophic calcification. Follow-up bone scans obtained because of the patient’s increased prostate-specific antigen levels have shown neither significant change in appearance of the scintigraphic abnormality nor evidence of bony metastases.