Malignant Primary Bone Tumours

Very rare when considered alongside other forms of primary malignancy (<1% of all new malignancies)

Aetiology

• Majority are idiopathic

• Can occur at any age but more common in young patients - 10% of childhood cancers

Risk factors

• Previous radiotherapy

• Predisposing conditions: Paget's, fibrous dysplasia, multiple enchondromas

• Genetic causes: Li Fraumeni syndrome (p53), familial retinoblastoma (RBI)

Clinical presentation

Symptoms

• Presentation is often late in the disease

• Higher index of suspicion in younger patients (10-30 years)

• Persistent, increasing pain
• Usually not associated with movement
• Well localised
• Worse at night
• Not uncommonly misdiagnosed for muscular pains - any unexplained persistent skeletal pain/red flags should be further investigated

• Pathological fracture

Signs

• Swelling and erythema over joint (especially in Ewing's sacroma)

• Palpable mass

Types of malignancy

Multiple myeloma

• Malignant disease of the plasma cells of the bone marrow

• Commonest primary tumour of bone

• Generally affects elderly patients

• 4 main features are hypercalcaemia, anaemia, renal impairment and bone pain

Osteosarcoma

• Malignant tumour which produces bone

• Most common primary sarcoma of bone

• Metastatic spread is usually haematogenous but can be lymphatic

• Most cases seen in adolescence and early adulthood

• 2nd peak in the elderly associated with Paget's

• 60% involve the bones around the knee (distal femur/proximal tibia), other sites include proximal femur, proximal humerus and pelvis

• 10-20% of patients have pulmonary metastases at diagnosis - impacts survival

Chondrosarcoma

• Cartilage producing primary bone tumour - malignancy of chondrocytes

• Less common and less aggressive than osteosarcoma (generally - can be aggressive)

• Majority arise de novo, few arise from benign lesions (enchondroma, osteochondroma)

• Prognosis dependent on histological grade - majority are low grade

• Can be very large and are slow to metastasize

• Tends to be found in the older age group - mean age 45

• Tend to be found in the pelvis or proximal femur

Fibrosarcoma and malignant fibrous histiocytoma

• Fibrous malignant primary bone tumours which tend to occur in abnormal bone e.g. bone infarct, post radiation

• Fibrosarcoma tends to affect adolescents/YAs

Ewing's sarcoma

• Primary bone tumour of the endothelial cells of the bone marrow

• 2nd commonest malignant bone tumour in children

• Characterised by loss of bone (lysis)

• Affects young people 5-25 years of age, most common age 10-20

• Hot, swollen, tender joint or limb with raised inflammatory markers - can mimic infection

• Usually found in diaphysis of long bones - distal femur, proximal tibia

Investigations

• X-ray - aggressive and destructive signs including cortical destruction, a periosteal reaction, new bone formation (sclerosis and lysis), reactive cortical thickening (chondrosarcoma) and extension into the surrounding soft tissue envelope
• AP and lateral including joint above and below
• Bony lesions may not show up on x-rays until more than 50% of the cortical bone is lost - if x-ray normal but clinical suspician is high perform further imaging

• Biopsy required for histological diagnosis and grading before surgery

• Staging - bone scan, CT, MRI

Management

• Surgery - removal of tumour and surrounding tissue, with joint reconstruction
• Typically margin of 3-4cm of bone and a cuff of normal muscle all around
• Amputations were more commonly used in the past but with improved adjuvant therapy limb salvage surgery has equivalent sucess rate (if appropriate)

• Adjuvant chemotherapy/radiotherapy used if appropriate
• Chondrosarcomas are not radiosensitive and are unresponsive to adjuvant chemotherapy
• Osteosarcomas are not radiosensitive but adjuvant chemotherapy can prolong survival

• Neo-adjuvant chemotherapy can improve survival