Pathological Fracture - Unknown Primary
CIM Case: Pathological Fracture - Unknown Primary
Clinical Scenario
Patient: 68-year-old man Presentation: Sudden onset left thigh pain after standing from chair, unable to weight-bear, preceded by 6-week history of dull aching left thigh pain Relevant history: 40 pack-year smoking history (stopped 5 years ago), 8kg weight loss over 3 months, decreased appetite, productive cough for 2 months, no prior malignancy diagnosed, retired carpenter (asbestos exposure) Examination findings:
- Cachectic appearance
- Left leg shortened and externally rotated
- Obvious deformity at mid-thigh level
- Palpable mass around fracture site
- Exquisitely tender at fracture site
- Unable to perform SLR
- Neurovascularly intact distally
- Finger clubbing noted
- Scattered rhonchi on chest auscultation
- No palpable lymphadenopathy
Investigations Provided
Laboratory Results
| Test | Result | Normal Range | Interpretation |
|---|---|---|---|
| Hb | 98 g/L | 130-170 g/L | ↓ Anaemia of chronic disease |
| WCC | 11.2 ×10⁹/L | 4-11 ×10⁹/L | ↑ Mildly elevated |
| Platelets | 425 ×10⁹/L | 150-400 ×10⁹/L | ↑ Reactive |
| CRP | 85 mg/L | <5 mg/L | ↑ Elevated |
| ESR | 95 mm/hr | <20 mm/hr | ↑ Markedly elevated |
| Calcium | 2.85 mmol/L | 2.2-2.6 mmol/L | ↑ Hypercalcaemia |
| ALP | 320 U/L | 30-120 U/L | ↑ Elevated (bone/liver) |
| Albumin | 28 g/L | 35-50 g/L | ↓ Hypoalbuminaemia |
| Creatinine | 125 μmol/L | 60-110 μmol/L | ↑ Mild renal impairment |
| PSA | 2.5 ng/mL | <4 ng/mL | Normal |
| Protein electrophoresis | No paraprotein | - | Excludes myeloma |
Imaging
Image 1: AP and Lateral Radiographs of Left Femur
Radiological features:
- Transverse fracture through mid-diaphysis of left femur
- Large lytic lesion at fracture site (5cm)
- Cortical destruction >75%
- Moth-eaten/permeative margins
- No matrix mineralisation (not bone-forming)
- Pathological fracture through tumour
- No periosteal reaction
Image 2: CT Chest/Abdomen/Pelvis
Findings:
- 4.5cm spiculated mass in right upper lobe (highly suspicious for primary lung carcinoma)
- Ipsilateral hilar lymphadenopathy
- Multiple small pulmonary nodules bilaterally
- Lytic lesion in L3 vertebral body
- No liver metastases
- No renal mass
- No adrenal masses
Questions & Model Answers
What is your differential diagnosis and most likely diagnosis?
Describe your workup for carcinoma of unknown primary (CUP).
How would you assess the risk of pathological fracture using Mirels score?
How would you manage this pathological fracture?
What is the prognosis and how does this affect your surgical decision-making?
What if this patient had a solitary renal metastasis instead?
Key Teaching Points
Pattern Recognition
This pattern suggests Metastatic Carcinoma:
- Adult >40 years with destructive bone lesion
- Constitutional symptoms (weight loss, fatigue)
- Lytic lesion without matrix production
- Risk factors for primary malignancy (smoking)
- Hypercalcaemia
Common Lytic Metastases (Mnemonic: "Kidney-Thyroid-Lung-Breast-Lick-Bone"):
- Kidney (renal cell)
- Thyroid
- Lung
- Breast
Common Blastic Metastases:
- Prostate (most common)
- Breast (can be mixed)
- Carcinoid
- Medulloblastoma
Critical Management Points
- Stabilise fracture first - don't delay for exhaustive workup
- Tissue diagnosis from fracture site - confirms primary
- Long nail for femoral shaft - protects entire bone
- Mirels score for impending fractures - ≥9 needs prophylactic fixation
- Adjuvant radiotherapy - improves local control
- MDT discussion - oncology, palliative care, radiation oncology
- Quality of life focus - palliative intent in most cases
Common Examiner Follow-ups
Q: "What are the most common sites for bone metastases?"
Most common sites (in order):
- Spine (thoracic > lumbar > cervical)
- Pelvis
- Proximal femur
- Ribs
- Proximal humerus
- Skull
Metastases occur in red marrow areas due to rich blood supply and Batson's venous plexus.
Q: "When would you consider curative resection for bone metastases?"
Curative resection may be considered when:
- Solitary skeletal metastasis confirmed on staging
- Primary controlled or controllable (nephrectomy for RCC)
- Long disease-free interval (>2 years)
- Favourable histology (RCC, thyroid, breast)
- Patient fit for major surgery
- Acceptable limb function expected post-resection
Most common scenario: solitary renal cell carcinoma metastasis
Q: "What is the role of radiotherapy in bone metastases?"
| Indication | Dose | Purpose |
|---|---|---|
| Palliation (pain) | 8 Gy single fraction | Quick pain relief |
| Post-operative | 30 Gy in 10 fractions | Local control |
| Spinal cord compression | 20-30 Gy | Decompression if non-surgical |
| Impending fracture (low Mirels) | 30 Gy | Prevent fracture |
Most bone metastases are radiosensitive except renal cell and melanoma.
Q: "How do you differentiate a pathological fracture from a traumatic fracture in the elderly?"
| Feature | Pathological | Traumatic |
|---|---|---|
| Mechanism | Minimal trauma | Significant trauma |
| Prodromal pain | Common (weeks) | Absent |
| X-ray | Lytic lesion, cortical destruction | Normal bone prior to fracture |
| Constitutional symptoms | Weight loss, fatigue | Absent |
| Risk factors | Malignancy history, smoking | Falls risk, osteoporosis |
Any fracture with minimal trauma or visible lesion on X-ray should be considered pathological until proven otherwise.
Related Topics
- Mirels Scoring System
- Bone Metastasis Management
- Intramedullary Nailing for Pathological Fractures
- Renal Cell Carcinoma Metastases
- Preoperative Embolisation
- Palliative Orthopaedics