Primary osteogenic sarcoma of the sternum with intravascular invasion and rapid progression: a rare case report.

Introduction and importance: Primary osteosarcoma of the sternum is a rare malignant bone tumor. Only a few cases have been documented, and most have been managed with chemotherapy and surgical intervention. Our case is distinctive due to the vascular invasion of the left brachiocephalic vein and lack of response to chemotherapy. Reporting this case contributes to the limited literature and highlights the diagnostic and therapeutic challenges associated with the management of primary sternal osteosarcoma. Case presentation: We describe a 37-year-old woman with a painful, progressively enlarging manubrial swelling. Imaging revealed a destructive sternal mass with mediastinal extension, pulmonary and nodal metastases, and a thrombus extending from the left brachiocephalic vein to the superior vena cava. Magnetic resonance imaging confirmed soft tissue infiltration, cardiac compression, and worsening pericardial effusion. Biopsy revealed malignant osteoid-forming cells with SATB2 positivity, confirming the diagnosis of primary sternal osteosarcoma. She received three cycles of doxorubicin and cisplatin, but her condition rapidly progressed. Regorafenib was initiated as salvage therapy; however, her condition worsened, and she died within 6 months of diagnosis. Clinical discussion: Primary osteosarcoma of the sternum is a rare and aggressive malignancy in adults. Imaging is crucial for staging and planning surgery. Standard treatment includes neoadjuvant chemotherapy with wide excision and reconstruction, whereas targeted therapies such as regorafenib may be considered for metastatic diseases. Conclusion: This case illustrates an exceptionally aggressive tumor complicated by vascular invasion and mediastinal involvement. This underscores the importance of early recognition to avoid diagnostic delays and demonstrates the limited efficacy of conventional chemotherapy in advanced disease. The use of regorafenib highlights the emerging systemic options that may be explored in refractory osteosarcoma. Our report emphasizes the urgent need for early diagnostic practices and a multidisciplinary approach to treatment.