Muscle Metastases as the Clinical Presentation of Renal Cell Carcinoma

Introduction: Muscle metastases are a rare form of clinical presentation in almost any type of cancer. Less than 1% of cases are reported in which the diagnosis is made based on musculoskeletal symptoms. The aim of this report is to present a clinical case in which the patient initially presented with persistent muscle pain in the left forearm and gluteal region, unresponsive to analgesics. This prompted further evaluation with imaging studies and subsequent surgical intervention. Case Description: An 82-year-old male patient presented for evaluation due to muscle pain in the right forearm and left gluteal region, ongoing for approximately 18 months. He reported having been treated with multiple analgesics without improvement. He denied any family history of cancer. Physical examination revealed a 1.5 cm mobile, non-tender mass with irregular borders in the right forearm. Additionally, a 3.5 cm mass with irregular borders was palpated in the left gluteal region. An X-ray followed by a CT scan was performed, revealing images consistent with metastases. An abdominal CT scan further documented a renal mass. Muscle biopsies confirmed the presence of muscle metastases from a clear cell renal carcinoma. The patient was referred to the urology department for further medical and surgical management. Discussion: The presentation of renal cell carcinoma through muscle metastasis is uncommon. In this case, the absence of urological symptoms is notable , the patient did not present with hematuria or flank pain. The literature contains only a few reports documenting renal carcinoma initially presenting with muscular symptoms. Skeletal muscle has several characteristics that contribute to the low incidence of metastases, including the presence of protease inhibitors, acidic pH, muscle contractions, and a lack of specific receptors necessary for metastatic cell growth and development. In most cases, the treatment of muscle metastases is palliative. However, surgical resection with clear margins may be used for local disease control. Chemotherapy and radiotherapy have not proven to be effective.