Arriving at a diagnosis — imaging & biopsy in orthopaedic oncology

Plain radiographs are the starting point because they are fast, low-dose and widely available. An X-ray shows tumour characteristics, the pattern of bone reaction and any risk of pathological fracture, and helps decide which advanced imaging to request next.

Evidence shows X-rays remain the primary screening tool for bone lesions, helping distinguish benign from aggressive patterns.2

Ultrasound differentiates solid from fluid-filled (cystic) lesions, shows blood flow within a mass and provides real-time guidance for needle biopsies — all without radiation.

Recent studies demonstrate ultrasound-guided core needle biopsy achieves 84–96% diagnostic accuracy for soft-tissue tumours at specialised centres.45

MRI provides superior soft-tissue contrast without radiation. It measures exact tumour dimensions, identifies “skip lesions” in the same bone and demonstrates the tumour's relationship to nerves, vessels and joints — all essential for surgical planning.

MRI detects joint invasion with 92–100% sensitivity and specificity when direct signs are present.1

CT is reserved for detailed bone anatomy (cortical detail, complex pelvic/spinal lesions, surgical planning) and a chest CT to screen for lung metastases.

High-resolution chest CT detects lung metastases in 15–20% of sarcoma patients at diagnosis, directly influencing treatment decisions.

Image-guided biopsy is the most critical diagnostic step. Under US, CT or MRI guidance, a narrow needle samples the most representative part of the tumour, confirming exact subtype and grade and providing tissue for molecular tests. The biopsy tract must align with the future surgical resection — placement by an experienced orthopaedic oncology team protects future limb-salvage options.

• Overall diagnostic accuracy: 93–99% for musculoskeletal tumours 6
• Ultrasound-guided: 96.5% diagnostic yield for soft-tissue masses 7
• CT-guided: ~90% accuracy for bone lesions 9
• MRI-guided: 97.6% accuracy with 100% specificity 10

PET-CT combines metabolic and anatomic imaging to map all active tumour sites in one study, separate tumour from scar or infection, and assess response to chemotherapy.

18F-FDG PET-CT detects additional metastases in 21% of Ewing sarcoma patients and offers 91–95% sensitivity for high-grade sarcomas.3

A whole-body bone scan can be a cost-effective alternative to PET-CT for detecting skeletal metastases, particularly in osteosarcoma where skeletal metastases occur in about 10% of patients. Specificity is limited, so suspicious findings are usually confirmed with MRI or CT.

Whole-body MRI scans the entire body without radiation and excels at detecting bone-marrow and soft-tissue metastases. In myxoid liposarcoma it has been shown to change management in roughly 30% of patients by detecting extra-pulmonary spread missed on CT.