Tl-201 and Tc-99m HMDP scintigraphic findings in extraskeletal osteosarcoma

Extraskeletal osteosarcoma is an extremely rare high-grade malignant soft tissue tumor, which accounts for approximately 4% of osteosarcomas and less than 1% of all soft tissue sarcomas. There have been reports describing the scintigraphic findings of this tumor, especially with Tl-201. We report a biopsy-proven case of extraskeletal osteosarcoma in which the bone and thallium scans were found to be useful in monitoring chemotherapy response. The Tc-99m HMDP bone scan revealed increased extraskeletal uptake in the tumor.