99mTc-Methylene Diphosphonate Uptake in Soft Tissue Tumors on Bone Scintigraphy Differs Between Pediatric and Adult Patients and Is Correlated with Tumor Differentiation

Objective: To analyze the difference in Tc-99m-methylene diphosphonate (MDP) uptake on bone scintigraphy in extraosseous soft tissue tumors between children and adults and the correlation between tracer uptake and tumor differentiation and histopathology. Methods: Patients with neoplasms with MDP uptake were retrospectively identified. Based on histopathology, tumors were categorized as epithelial malignant tumors, mesenchymal tumors, blastomas and germ cell tumors. The degree of radioactivity accumulation in lesions relative to the uptake in ribs and sternum or spine was classified as "+", "++" and "+++". The results were compared between children and adults. The correlations between MDP uptake in soft tumors and tumor differentiation and pathology were investigated. Results: Extraosseous soft tissue tumors that accumulated MDP were found in 33 children and 31 adults. In children, neuroblastoma was the most common extraosseous soft tissue tumor that accumulated MDP; in adults, MDP uptake was mostly found in lung cancer. MDP uptake in pediatric soft tissue tumors was higher than that in adults. MDP uptake in extraosseous soft tissue tumors with different histopathologic classifications was significantly different among 64 patients. In 41 patients with available tumor differentiation data from histopathology, MDP uptake in low or poorly differentiated soft tumors was higher than that in the moderately or well-differentiated lesions. Necrosis and/or calcifications were showed in most of pediatric and adult neoplasms. Conclusion: Significant elevations in MDP uptake in extraosseous soft tissue tumors are associated with poorly differentiated tumors in both children and adults. The mechanism of bone tracer uptake in pediatric and adult neoplasms was mostly related to necrosis and/or necrosis and calcification. The extraosseous soft tissue tumors with MDP uptake in pediatric patients were different from those in adults. In addition, consistent with the inherent degree of tumor malignancy, MDP uptake in children was higher than that in adults.