We report the case of a 43-year-old woman who presented with mild left-sided abdominal pain. Computed tomography and MRI findings revealed a 10.7 × 8.5 × 12 cm left-sided soft tissue mass on the renal vessels pushing away the left kidney. The combination of the patient's medical history (episodes of paroxysmal hypertension accompanied with dizziness and sweating) and radiological findings initially pointed toward the diagnosis of a paraganglioma or ectopic pheochromocytoma. Surgical removal of the tumor and left nephrectomy was performed. Histological findings were consistent with a renal vein leiomyosarcoma of a high malignancy grade. There is no evidence of local recurrence or metastatic disease for more than 2 years postoperatively, although the patient did not receive adjuvant chemotherapy or radiation therapy.