Ultrasound has limited capabilities in assessment of bone tumours: Myth debunked
By Louise Fitzgerald, University Hospital Limerick
Background
A 73-year-old male was referred to the ultrasound department after discovering an acute swelling at the region of the jugular notch. The swelling was mildly tender, not well defined, hard and non-mobile. An x-ray of the sternum and chest were performed, neither of which detected any abnormalities. A soft tissue ultrasound of the lump was requested for further assessment.
Ultrasound Findings
Sonographic evaluation illustrated a 5.8cm x 4.7cm x 5.4cm well defined, solid, heterogeneous mass with no retrosternal extension. The mass illustrated multiple prominent blood vessels on colour Doppler and demonstrated high velocity arterial flow on spectral Doppler. The consultant radiologist suggested that this lesion was thymic or nodal in origin and recommended a computed tomography (CT) thorax for additional evaluation.
Discussion
The CT thorax confirmed the presence of a heterogeneous enhancing lesion at the left costosternal joint extending into the manubrium sternum. This lytic lesion was not a soft tissue lesion but of bony origin. Ultrasound permits the evaluation of the bone surfaces only due to the difference in acoustic impedance between soft tissues and the bone cortex. However, in this case, the interruption of the cortex of the bone by the lytic lesion allowed visualisation of the intraosseous mass.
Further CT imaging of the abdomen identified an irregular enhancing lesion at the inferior pole of the right kidney, suspicious for renal cell carcinoma. An ultrasound guided biopsy of the sternal lesion confirmed bone metastases from renal cell carcinoma.
Conclusion
Ultrasound is the modality of choice for the evaluation of palpable soft tissue masses. Indeed, its utility should not be underestimated in the assessment of bone lesions. Ultrasound plays a pivotal role in the diagnosis of renal cell carcinoma and the metastatic process; either by identifying thrombus in the renal vein or metastases to the bone.