Renal Cell Carcinoma is the Most Likely Primary Source
Renal cell carcinoma (RCC) is the most likely primary cancer causing these expansile spinal metastases with compressive myelopathy in this previously healthy 57-year-old woman. The clinical presentation of multiple expansile vertebral lesions causing cord compression, combined with the patient's age and lack of prior cancer history, strongly points toward RCC as the primary source.
Key Distinguishing Features Supporting RCC
Expansile bone metastases are characteristic of renal cell carcinoma, which produces highly vascular, lytic lesions that expand and destroy vertebral bodies 1, 2. This expansile quality differentiates RCC from other common spinal metastases:
- Breast cancer typically produces mixed lytic-sclerotic lesions but is less commonly expansile 2
- Lung cancer produces predominantly lytic lesions but rarely causes the dramatic vertebral expansion seen here 2
- Prostate cancer produces predominantly sclerotic (not expansile) metastases 3, 2
Epidemiologic Support
RCC accounts for a substantial proportion of spinal metastases despite representing only 1% of all cancers 4. The spine is the most frequent site of skeletal involvement in RCC, with bone metastases occurring in 30-40% of patients with advanced disease 1, 2. More than 50% of all spinal metastases originate from breast, lung, prostate, or renal primary tumors 2.
In patients presenting with spinal cord compression as the first manifestation of cancer (as in this case), RCC must be strongly considered 3. Studies show that 47% of patients with spinal metastases present with the spinal lesion as their first evidence of malignancy 5.
Why the Other Options Are Less Likely
- Basal cell carcinoma: Virtually never metastasizes to bone or spine
- Cervical adenocarcinoma: Rarely metastasizes to spine; when gynecologic cancers do metastasize to bone, ovarian cancer is more common 3
- Ovarian adenocarcinoma: Has extremely low lifetime risk of spinal cord compression (0.048% in asymptomatic patients with no risk factors) 3
- Primary CNS lymphoma: Does not produce expansile vertebral metastases; remains confined to CNS structures 3
Clinical Implications for This Patient
The patient requires urgent neurosurgical evaluation and tissue diagnosis given the compressive myelopathy 3. RCC metastases are relatively radioresistant, making surgical decompression often necessary for cord compression 3.
Stereotactic body radiotherapy (SBRT) achieves approximately 90% local control at 1 year for RCC spinal metastases and should be considered as adjuvant therapy post-decompression 3, 1. The highly vascular nature of RCC metastases increases surgical bleeding risk but also makes these lesions amenable to preoperative embolization 4.
Bone-modifying agents (zoledronic acid or denosumab) should be initiated once the diagnosis is confirmed, as RCC produces predominantly osteolytic lesions with high risk of skeletal-related events 3, 1.