Bone Neoplasia — Primary & Secondary

Secondary (metastatic) bone disease

Secondary bone cancer is far more common than primary bone cancer in Australia. Common primaries causing bone metastases: prostate, breast, lung, kidney, thyroid cancer, myeloma, melanoma.

• Osteolytic: bone is broken down without new bone formation (“lytic” lesions).
• Osteoblastic: bone is formed and grows abnormally.
• Identified on bone scan, CT/MRI or PET scan; be suspicious with an elevated calcium.

Signs and symptoms: bone pain (dull, persistent, often worse at night), pathological fractures, elevated calcium, neuropathic pain from nerve outlet obstruction/pressure.

Primary bone tumours

Osteosarcoma

A rare mesenchymal tumour characterised by malignant cells producing osteoid (immature bone).

• Demographics: bimodal — adolescents (10–19 years) and adults >60.
• Risk factors: largely unknown cause; genetic tumour syndromes; prior radiation to the area; Paget disease of bone.
• Presentation: localised pain and/or swelling, pathological fractures; pain typically dull, aching, persistent. Adults — commonly lower long bones and pelvis. Children/adolescents — lower long bones (75%), upper long bones (11%).
• Metastasis: commonly to lungs and other bones.
• Examination: bony tenderness at the complaint site; examine the lungs (though imaging will be needed regardless).
• Investigations: typically diagnosed on X-ray, then full staging imaging — MRI of the primary site, MRI/CT of skeletal metastatic sites, CT chest, PET or bone scan.
• Management: refer to oncology + orthopaedic surgery/MDT — surgical resection, chemotherapy, radiation, staging-dependent.
• Prognosis: 5-year relative survival in children <19 is ~70%, but long-term survival for recurrent, unresectable, or metastatic-at-diagnosis disease is poor.

Osteochondroma

The most common benign bone tumour — a cartilage-capped bony projection arising from the external bone surface, with a marrow cavity continuous with the underlying bone.

• Demographics: non-hereditary form affects children/adolescents equally by sex; hereditary multiple osteochondromas usually present in the first decade (including infancy), male:female ~3:1, more common in Caucasians.
• Presentation: typically a painless, slow-growing mass near a joint. Complications: fracture, bone deformity, joint problems. Common sites — non-hereditary: tibia, femur, humerus; hereditary: long bones, especially around the knee. Hereditary multiple osteochondromas can cause orthopaedic deformity (ulna shortening, short stature, unequal limb length, knee varus/valgus, ankle deformity).
• Red flags for malignant transformation: increasing localised pain, an enlarging palpable mass, nocturnal pain or pain at rest, weight loss/ night sweats, or growth continuing after puberty.
• Investigations: X-ray; biopsy if malignant transformation is suspected (post-pubertal growth, pain, cartilage cap thickness >3cm in children).
• Management: usually observation and symptom control; orthopaedic opinion worthwhile; surgical excision for persistent pain, complications, cosmesis, or suspected malignant transformation.

Ewing sarcoma

A rare small round blue-cell tumour of unknown origin, arising from bone or soft tissue.

• Demographics: mainly children and adolescents (median age 15).
• Presentation: localised, non-mechanical pain and/or swelling; may have fever, weight loss or fatigue. Metastasis to bone (10%), bone marrow (10%) and lungs (10%).
• Investigations: primary-site plain X-ray, follow-up MRI/CT; biopsy required for histological diagnosis.
• Management: refer to a multidisciplinary paediatric oncology team — multiagent chemotherapy, surgical resection ± radiation therapy.