Metastatic Renal Cell Carcinoma to Humerus
CIM Case: Metastatic Renal Cell Carcinoma to Humerus
Clinical Scenario
Patient: 58-year-old man Presentation: Progressive left arm pain for 8 weeks, now with difficulty lifting objects, pain at night disturbing sleep Relevant history: Renal cell carcinoma diagnosed 2 years ago (right nephrectomy, clear cell type, T3aN0M0 at diagnosis), recent surveillance CT showed no recurrence in renal bed, no prior chemotherapy, otherwise well, smoker (20 pack-years), no other medical history Examination findings:
- Well-appearing man, no cachexia
- Tender mass palpable over mid-left humerus (firm, fixed to bone)
- Overlying skin normal, warm to touch
- Full shoulder and elbow range of motion (limited by pain)
- No wasting of deltoid or arm muscles
- Neurovascularly intact distally (radial pulse normal)
- Lungs clear on auscultation
- Abdomen soft, left nephrectomy scar healed
Investigations Provided
Laboratory Results
| Test | Result | Normal Range | Interpretation |
|---|---|---|---|
| Hb | 125 g/L | 130-170 g/L | ↓ Mildly low |
| WCC | 7.8 ×10⁹/L | 4-11 ×10⁹/L | Normal |
| Platelets | 245 ×10⁹/L | 150-400 ×10⁹/L | Normal |
| CRP | 12 mg/L | <5 mg/L | ↑ Mildly elevated |
| ESR | 35 mm/hr | <20 mm/hr | ↑ Elevated |
| Calcium | 2.75 mmol/L | 2.2-2.6 mmol/L | ↑ Elevated |
| ALP | 185 U/L | 30-120 U/L | ↑ Elevated |
| Albumin | 38 g/L | 35-50 g/L | Normal |
| LDH | 280 U/L | 120-250 U/L | ↑ Mildly elevated |
| Creatinine | 115 μmol/L | 60-110 μmol/L | ↑ Mildly elevated (single kidney) |
| eGFR | 58 mL/min | >60 | ↓ Stage 3 CKD |
Imaging
Image 1: AP and Lateral Radiographs of Left Humerus
Radiological features:
- Large lytic lesion in mid-diaphysis of humerus
- Geographic destruction with moth-eaten margins
- Cortical erosion (>50% circumference involved)
- No matrix mineralisation
- Soft tissue mass visible extending from bone
- No periosteal reaction
- No pathological fracture yet
- Lesion spans approximately 8cm longitudinally
Image 2: CT Chest/Abdomen/Pelvis (Staging)
Findings:
- Right nephrectomy (known)
- No renal bed recurrence
- No liver metastases
- Solitary 5mm pulmonary nodule in right lower lobe (indeterminate)
- No other bone lesions on CT
- No lymphadenopathy
Image 3: Bone Scan (Whole Body)
Findings:
- Hot lesion in mid-left humerus
- Cold centre (photopenic) with hot rim
- No other skeletal lesions
- Normal uptake in kidneys/bladder
Questions & Model Answers
What is your differential diagnosis and most likely diagnosis?
What is the fracture risk and how would you assess it?
What is the staging workup and significance of the solitary metastasis?
What is the role of preoperative embolisation?
What are the surgical options for this lesion?
What is the prognosis and what systemic treatment options exist for metastatic RCC?
Key Teaching Points
Pattern Recognition
This pattern suggests Renal Cell Carcinoma Bone Metastasis:
- History of RCC (even remote)
- Lytic, expansile bone lesion
- Hypercalcaemia
- Hypervascular appearance on imaging
- Hot lesion with cold centre on bone scan (vascular tumour necrosis)
- Late presentation (years after primary)
Lytic Bone Metastases Mnemonic: "Lots of Trouble Kills Patients Badly":
- Lung
- Thyroid
- Kidney
- Prostate (usually blastic, can be lytic)
- Breast
Critical Management Points
- Confirm solitary - PET-CT before planning curative surgery
- Preoperative embolisation - ESSENTIAL for RCC (highly vascular)
- Mirels score ≥9 - prophylactic fixation indicated
- Wide excision for curative intent - if truly solitary, 2-3cm margins
- MDT approach - oncology, orthopaedics, IR, radiology
- Bone-modifying agents - reduce skeletal events
- Long-term surveillance - RCC can recur late
Common Examiner Follow-ups
Q: "What is the 'cold in hot' sign on bone scan and what does it indicate?"
The "cold in hot" or "doughnut" sign:
- Peripheral hot rim with central photopenic (cold) area
- Indicates highly vascular tumour with central necrosis
- Classic for renal cell carcinoma metastases
- Also seen in aggressive vascular tumours
Mechanism: The centre has outgrown its blood supply leading to necrosis, while the periphery remains hypervascular and metabolically active.
Q: "Why is RCC relatively radioresistant and what are the implications?"
RCC is considered radioresistant because:
- Conventional fractionated RT has limited efficacy
- May relate to hypoxic tumour microenvironment
- VHL pathway mutations affect hypoxia response
Implications:
- Surgery preferred for local control when feasible
- Stereotactic body radiotherapy (SBRT) more effective (high dose per fraction)
- Radiotherapy alone not reliable for local control
- Post-operative RT role is limited
Q: "How do you manage the 5mm lung nodule?"
Management of indeterminate lung nodule:
- Repeat CT in 3-6 months (Fleischner Society guidelines)
- If stable for 2 years: likely benign
- If growing: biopsy or resection
- PET-CT has limited sensitivity for lesions <8mm
- Changes surgical plan if proven metastatic (no longer solitary)
For this patient:
- If nodule is stable/benign: proceed with curative resection of humerus
- If nodule is metastatic: palliative approach more appropriate
Q: "What are the indications for amputation in this scenario?"
Amputation indications for bone metastasis (rare):
- Massive neurovascular involvement not reconstructable
- Failed limb salvage with infection
- Uncontrollable haemorrhage
- Fungating tumour with skin breakdown
- Patient preference after informed discussion
For this patient with localised disease, limb salvage should be achievable with modern techniques.
Related Topics
- Pathological Fractures
- Mirels Scoring System
- Preoperative Embolisation
- Endoprosthetic Reconstruction
- Bone Metastasis Management
- Immunotherapy in Oncology