Solitary vertebral metastasis of unknown primary renal cell carcinoma treated with surgical resection plus tyrosine kinase inhibitor: A case report

Introduction: Although 25-30 % of renal cell carcinomas (RCC) might be diagnosed in metastatic stage, occurrence of metastatic renal cell carcinoma (mRCC) as a cancer of unknown primary site (CUP-mRCC) is extremely rare. Here, we present a case of vertebral mass causing radicular pain that has been diagnosed to be mRCC through core needle biopsy while no renal mass has been found during serial imaging. Case presentation: A 60-year-old woman presented with severe lumbar pain radiating to left leg. Lumbar X-ray suggested a mass in second lumbar vertebra which was confirmed by MRI. Biopsy showed that the mass was clear cell RCC. Abdominopelvic CT scan and other metastatic work-up found no primary source for the cancer -in kidneys- nor any other metastasis. Tumor resection was performed followed by sunitinib administration. 3 months after the surgery, she is symptom free with no signs of disease progression nor kidney tumor. Discussion: 26 cases of CUP-mRCC has been reported in literature. Lymph nodes are the most commonly involved organ in CUP-mRCC. Exclusive bone involvement -similar to our case- have been reported in only 3 cases. No specific treatment guideline exists but surgery, systemic therapy, combination therapy, and radiotherapy have been used, with the first two items being the most commonly used ones. Conclusion: Tumor resection plus sunitinib seems to be a reasonable option in solitary CUP-mRCC involving vertebral column. Our patient is symptom free and there are no signs of disease progression nor kidney cancer in follow-up imaging after 3 months of surgery.