Abstract

Purpose: Renal cell carcinoma (RCC) is the most common malignant kidney tumor, commonly metastasizing to the lung, lymph nodes, bones, and brain. Here, we present a rare case of renal cell skeletal muscle metastases (SMM), accounting for only <1% of all RCC metastases.
Methods: This is a descriptive report on the clinical course, diagnostic investigations, and surgical treatment of a case of SMM in a patient previously diagnosed with RCC.
Results: This is a 58-year old male who previously underwent radical nephrectomy for RCC, presenting with a 5- month history of a rapidly enlarging left gluteal mass. The mass was confirmed to be renal clear cell metastasis via percutaneous biopsy. On magnetic resonance imaging (MRI), two heterogeneously enhancing lesions in the left gluteal muscle and right paralumbar muscles at the level of L4 and L5 were noted. Positron-emitted tomography (PET) scan confirmed no other metastases. He underwent wide excision of the right paraspinal mass and buttockectomy for the left gluteal mass.
Conclusion: SMM in RCC is rare, thus tissue diagnosis and imaging is deemed necessary to rule out any other primary sarcoma. In these cases, patients may benefit from metastasectomy. Regular follow up and surveillance is recommended for these patients to rule out recurrence.

Keywords: Renal cell carcinoma; Metatasis; Muscle metastasis; Extraskeletal metastasis; Buttockectomy