BACKGROUND
Clear cell renal cell carcinoma metastases in extremity musculature are very rare and often present a diagnostic challenge because of their resemblance to soft-tissue sarcoma. We present a rare case of delayed biceps brachii metastasis from clear cell renal cell carcinoma, which occurred 15 years after the initial diagnosis.
CASE REPORT
A 75-year-old Eastern European woman presented with a painful mass in her left arm. She had been diagnosed with and treated for clear cell renal cell carcinoma 15 years earlier. Physical examination demonstrated an oval-shaped soft-tissue mass in the proximal left arm. Ultrasound revealed a hypoechoic, well-vascularized soft-tissue tumor located in the biceps brachii muscle. Magnetic resonance imaging of the affected extremity showed a heterogeneous intramuscular tumor. Following multidisciplinary discussion, the patient underwent single-stage surgical treatment. The decision to proceed without a preoperative biopsy was specific to this case. Histological examination revealed metastasis from clear cell renal cell carcinoma. The patient had an uneventful postoperative course without functional deficit. After multidisciplinary restaging and evaluation, adjuvant immunotherapy was initiated. At the last follow-up, the patient had no complaints, signs of local recurrence, or functional deficits.
CONCLUSIONS
Skeletal muscle metastases from clear cell renal cell carcinoma have clinical and imaging characteristics that closely mimic those of soft-tissue sarcoma. Regardless of the disease-free interval, metastatic disease should be considered in the differential diagnosis when evaluating any new soft-tissue mass in affected patients. Our treatment strategy was individually selected for the present patient. Given the single-case nature of this report, our findings should not be considered a general management recommendation.

Keywords: Carcinoma, Renal Cell; Soft Tissue Neoplasms; Upper Extremity; Neoplasm Metastasis