Imaging findings of extrapulmonary metastases of osteosarcoma

To review imaging findings of extrapulmonary metastasis from osteosarcoma and to evaluate them for any consistent pattern and correlation between imaging findings.

This study was retrospectively conducted in 13 patients with extrapulmonary metastasis of pathologically confirmed osteosarcoma. We evaluated the radioisotope (RI) scans (n=16), ultrasonography (USG) (n=4), computed tomography (CT) scans (n=10), MRIs (n=6), clinical records, and pathological reports for assessment of imaging findings and correlation between radiologic findings and RI uptake of the lesions. Points evaluated were the following: uptake on RI scans, presence of mineralization on CT, and MRI, size, enhancement pattern, attenuation on CT, signal intensity (SI) on MRI, and echogenicity on USG.

Extrapulmonary metastatic sites were diverse, including another bone other than the primary site (n=6), lymph node (n=4), pleura (n=2), liver (n=2), pancreas (n=1), kidney (n=1), peritoneum (n=1), muscle (n=1), and subcutaneous fat layer (n=1). One patient had tumor growth within the pulmonary artery and jejunum. Among 21 metastatic sites in 13 patients, bone scan was performed in 16 cases and RI uptake was detected in 10 lesions. Calcification was detected in eight lesions on radiologic imaging, including plain radiography, USG, CT, and MRI. Two lesions showed RI uptake without definite calcification or ossification on MRI and plain radiography, respectively. We analyzed the enhancement pattern and mass size in 18 metastatic sites and these factors had poor correlation with uptake on RI scans.

The sites and imaging findings of extrapulmonary metastasis of osteosarcoma were variable. All the lesions with mineralization were detectable on RI scans prior to radiologic imaging. RI scan has a limited role in the evaluation of metastatic lesions without mineralization.