Smooth Muscle Tumor of Uncertain Malignant Potential Arising from Renal Vein

Smooth muscle tumors (SMTs) typically fall under either benign leiomyoma or malignant leiomyosarcomas based on histologic characteristics. SMTs that cannot be diagnosed as benign or malignant are then labeled as smooth muscle tumors of uncertain malignant potential (STUMP). A 31-year-old male presented with the right abdominal pain for 6 months. Imaging showed an enhancing soft-tissue mass arising from the right renal vein. A pre-operative biopsy confirmed STUMP of renal vein, and the patient underwent surgical resection of the mass with partial nephrectomy. Imaging and pathologic findings play a crucial role in an accurate pre-procedural diagnosis of unusual SMTs.