Osteosarcoma (OS) is a rare disease with approximately 800- 900 newly diagnosed cases each year in the United States. Of those, the majority occur about the knee. The distal femur is the most common site, followed by the proximal tibia, with the proximal humerus being a distant third. OS of the clavicle has been reported, with the earliest case report dating from 1975.1 Since then, additional case reports of high-grade OS of the clavicle have been published. 2,3 We describe the case of a 16-year-old female who presented with a mass on her right medial clavicle, which was confirmed to be a low-grade central OS.
Case Presentation
The patient is a 16-year-old female who presented to the Emergency Department (ED) for evaluation of a mass on her right clavicle, after being evaluated by her primary care physician (PCP). She noted an enlarging mass over the previous 2 months but stated that it had been asymptomatic until 4 days prior to presentation to her PCP, at which time she had developed tenderness to palpation and pain with range of motion of the right arm. X-rays were obtained at the PCP’s office and she was referred to the ED for further evaluation. She denied constitutional symptoms.
At the ED visit, she was noted to have an area of erythema and tenderness over the medial aspect of the right clavicle with increased bony prominence. A chest x-ray demonstrated medial clavicle enlargement with periosteal reaction and sclerosis (Figure 1) .
MRI demonstrated a 6-cm x 3.8-cm x 4.1-cm mass arising from the right medial clavicle with cortical destruction and concomitant displacement of the right subclavian and brachiocephalic veins (Figure 2) . A CT-guided biopsy was performed 1 week later and demonstrated low-grade OS. The pathologist was concerned about the possibility of sampling error and the presence of a higher-grade component, as low-grade OS of the clavicle had not been reported.
The patient was evaluated by a pediatric hematologist/oncologist 2 weeks later after having obtained the biopsy and a PET/CT scan. At that time, the PET/CT showed an FDG-avid mass at the clavicle without evidence of pulmonary metastatic disease (Figure 3) . She was subsequently evaluated by orthopedic oncology, at which time a discussion was had regarding further treatment. There was essentially no literature to guide the surgical and medical teams, as low-grade clavicular OS is unknown. Based on the evidence of localized, low-grade disease, the determination was made to proceedwith surgical resection. In the event that high-grade disease was identified at the time of final pathological evaluation, the pediatric hematology/oncology team felt that administering all of the patient’s chemotherapy postoperatively would be acceptable and not affect her long-term prognosis. CT and CT angiogram were obtained for further operative planning (Figure 4) .
Given the intimacy of the mass to the subclavian vessels, she was also seen preoperatively by pediatric general and cardiothoracic surgeons. The plan was formulated to have them in the operating room for mobilization of the subclavian vessels and in the event that a sternotomy was required for proximal control of the vessels. Following this visit, the case was discussed at the multidisciplinary pediatric tumor board and the consensus was to proceed with surgical resection.