DIFFERENTIAL-DIAGNOSIS OF ATYPICALLY LOCATED SINGLE OR DOUBLE HOT-SPOTS IN WHOLE BONE SCANNING

Our study assessed the predictive value of atypically located hot spot s in routine Tc-99m-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. Methods: Of 1286 scans in consecuti ve patients with a history of malignant tumor, but with no current evi dence of osseous tumor spread, 172 displayed one or two hot spots in t he following locations: transverse process of a single vertebra, manub riosternal 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 . Results: 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 i n the sternoclavicular joint never indicated malignancy. Conclusion: T he likelihood of atypically located isolated hot spots indicating osse ous 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 d id not indicate metastatic disease in our study.