Differential diagnosis of atypically located single or double hot spots in whole bone scanning

Our study assessed the predictive value of atypically located hot spots in routine 99mTc-DPD (3,3 diphosphono-1, 2-propane dicarboxylic acid tetrasodium salt) bone scanning for osseous tumor spread in patients with a history of malignant tumor.

Of 1286 scans in consecutive patients with a history of malignant tumor, but with no current evidence of osseous tumor spread, 172 displayed one or two hot spots in the following locations: transverse process of a single vertebra, manubriosternal junction, unilateral process of L5/S1, unilateral shoulder, costal cartilage, single rib, and unilateral sternoclavicular joint. The final diagnosis could be established by a control bone scan after at least 6 mo, biopsy and/or postmortem, respectively, in 135 patients.

Of the atypical hot spots, 11.1% were the first indication for osseous tumor spread. This diagnosis was most probable for single hot spots in the rib (25%) and shoulder (21%). Conversely, hot spots in the sternoclavicular joint never indicated malignancy.

The likelihood of atypically located isolated hot spots indicating osseous tumor spread is higher than expected during routine investigations in patients with a history of malignant tumor but no current evidence for malignant disease. Only hot spots in the sternoclavicular joint did not indicate metastatic disease in our study.