A challenging diagnosis: renal vein leiomyosarcoma, iniatially resembling a retroperitoneal tumor

Abstract

A 74-year-old male patient was referred to our hospital due to an incidental finding. CT scan and MRI revealed a retroperitoneal mass (4, 5 x 4,6 cm) in the hilum of right kidney. Which was in close contact with the second part of the duodenum, the uncinate process of pancreas, the right hepatic lobe and the infundibulum of gallbladder. CT scan also showed right hydronephrosis and no evidence of metastatic disease. An endoscopic-ultrasound-guided fine-needle-aspiration of the paraduodenal mass was performed, which was reported as a likely mesenchymal tumor. We carried out an open abdominal approach: there was a tumor arising from the right renal vein without involving adjacent structures. A right radical nephrectomy with en-bloc resection of the tumor was performed. Pathological exam revealed a well-differentiated leiomyosarcoma originated from the right renal vein with margins free from tumor. There was less than 50% of necrosis and 9 mitosis per 10 high-power fields. Cells stained positive for smooth muscle actin and desmin; and negative for S100 stain. Conclusion: Renal vein leiomyosarcomas are very difficult to diagnose preoperatively because USE, CT and MRI studies are nonspecific and do not allow an adequate differential diagnosis with other retroperitoneal tumors. The best treatment consists of complete surgical removal of the mass, including nephrectomy. The prognosis is bad and chemotherapy may be offered to cases with metastatic disease.