Primary Osteosarcoma of the Sternum with Lung Metastases

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A 55-year-old male patient, presenting with progressive, painful swelling at the anterior chest wall for 5 months duration, underwent complete radiologic evaluation and was diagnosed with osteosarcoma of the sternum with lung metastases (Figs 1 and 2; Movie). The patient had no history of chest infection, surgery, malignancy, or radiation. Histopathologic results and immunohistochemistry of the CT guided–biopsied specimens confirmed the diagnosis of osteoblastic osteosarcoma. Despite undergoing chemotherapy, the patient died within 6 months, as the response to chemotherapy and radiation is poor in unresectable metastatic sternal osteosarcomas.

Figure 1:

Images in a 55-year-old male patient with primary osteosarcoma of the sternum with lung metastases. (A, B) Frontal and lateral radiographs of the chest show a dense sclerotic lesion with extensive new bone formation involving the sternum (thick arrows) and a few well-defined nodules in the upper lobes of both lungs (thin arrows). (C) Axial chest CT image shows an irregular mixed attenuation lesion involving the sternum (arrow). Well-defined osseous metastases are observed in the upper lobes of both lungs (thin arrows). HU = Hounsfield units.

Figure 2:

(A) Sagittal chest CT bone window image shows extensive osteoid matrix, the hallmark of osteosarcoma, involving the manubrium and upper body of the sternum (arrow). (B) Sagittal T2-weighted fat-suppressed MRI scan reveals the tumor extension into the retrosternal anterior mediastinum with intact fat planes between the lesion and the great vessels (arrows). (C) Whole-body PET image shows a hypermetabolic sternal lesion, without any uptake elsewhere in the body, including lung nodules.

Movie:

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Three-dimensional volume-rendered images of the thorax show biopsy-proven primary osteosarcoma of the sternum along with ossified lung metastases.

Primary osteoblastic osteosarcoma of the sternum is an extremely uncommon, aggressive malignant bone tumor, reported to present as a rapidly enlarging, painful swelling of the anterior chest wall (1,2). Radiography and US have limited role in its evaluation, and MRI is unsatisfactory in demonstrating the characteristic osteoid matrix of osteosarcomas. Chest CT is the imaging modality of choice for evaluation, as it excellently depicts osteolytic bone destruction, osteoid matrix, and new bone formation, which are the characteristic features of osteosarcoma. Whole-body fluorine 18 fluorodeoxyglucose PET/CT has poor sensitivity in detecting small lung metastases of osteosarcoma, as in this patient (3).

Keywords: CT, MR Imaging, PET/CT, Skeletal-Axial, Thorax, Lung, Metastases, Neoplasms-Primary, Oncology