Advance MR evaluation of synchronous multifocal osteosarcoma with pathologic fracture.

Objective: Synchronous multifocal osteosarcoma is a rare condition in which the osteosarcoma presents with multiple bone lesions at the time of diagnosis, usually without any visceral metastases. The first case was described in early 1930s by Silverman. To report a case of synchronous multifocal osteosarcoma in adolescent with pathologic fracture.

Methods: An 18-year-old girl presented with a painful mass in the right thigh of 4 months' duration and a history of thigh bone fracture a month ago. Patient's medical records and family history was unremarkable. Physical examination showed angulation and shortening at right femoral region with tenderness and swelling. Initial radiograph and magnetic resonance (MR) images showed multiple lesions in right femoral shaft and pelvic bone with primary tumor in right distal femur with pathologic fracture and multiple bone marrow lesions found in the contralateral bones. Imaging and histopathological results supported the diagnosis of synchronous multifocal osteosarcoma. After following the chemotherapy as the treatment of choice, the radiograph and MRI evaluation were done and showed reduction of the mass size with union of the destructed part with the formation of callus. The advance MRI revealed reduction of the overall mass and the composition of the viable area compared to previous study. The patient had satisfying response to chemotherapy series and a better functional outcome on subsequent visits.

Results: Diagnosis of synchronous multifocal osteosarcoma was based on patient and family history and finding of multiple lesions in the MR images, meanwhile the plain radiograph only revealed the primary tumor. Amstutz described multifocal osteosarcoma as presence of one primary tumor and several smaller lesions. Most recent reviews concluded that multifocal osteosarcoma is bone-to-bone metastatic process rather than multicentric origin. The limitation in this case was absence of thoracic CT which is suggested to rule out any pulmonary metastases instead of routine chest radiograph.

Conclusion: Although satisfying improvement was clinically achieved, further advanced MRI would be indicated to evaluate the progression of tumor and its respond to therapy.