Serious Renal Hemorrhage in Masson Tumor V. Rizza, G. Coletti, P. Di Cocco, C. Mazzotta, A. Famulari, and F. Pisani ABSTRACT Intravascular papillary endothelial hyperplasia (IPEH; Masson tumor) is a vascular lesion of blood vessels, first described in 1923 by Masson, who termed it “hemangioendotheliome vegetant Intravasculaire.” This lesion consists of an exuberant, usually intravascular, proliferation of normal endothelial cells and is considered to be a reactive vascular proliferation after traumatic vascular stasis. The disease frequently occurs in skin and subcutaneous tissue; occurrence in solid organs is rare. We report a rare case IPEH that recurred as a possible consequence of an acute hypertensive arterial crisis in a patient with chronic kidney failure after kidney transplantectomy. Thirty days after transplantectomy, a 49-year-old white man receiving hemodialysis had pain in the left abdominal flank and acute anemia with serious hypovolemia after a hypertensive arterial crisis. An emergency non– contrast enhanced abdominal computed tomographic scan showed a massive retro- peritoneal hemorrhage. A left nephrectomy was performed for evidence of a native kidney breach with toilette of the abdominal cavity. Histologic analysis revealed that the renal lesion had several important distinguishing characteristics that confirmed the diagnosis of IPEH. This lesion is considered to be an usual form of thrombus organization that is marked by excessive papillary endothelial proliferation. In rare cases, it is present in a solid organ of the abdominal cavity especially the kidney. Intravascular papillary endothelial hyperplasia is a benign lesion but can be dangerous. Clinical, radiologic, and histologic diagnosis of IPEH is difficult. I NTRAVASCULAR papillary endothelial hyperplasia (IPEH) is rarely extravascular benign lesion described by Masson 1 in 1923. It consists of exuberant proliferation of endothelial cells in normal blood vessels or vascular mal- formations. 2 The lesion requires differential diagnosis from angiosarcoma. Masson described it as a form of neoplasm, regarding the pathogenesis as proliferation of endothelial cells into the blood vessel lumen followed by obstruction with subsequent secondary degeneration and necrosis. In fact, IPEH is considered to be a reactive vascular prolifer- ation following traumatic vascular stasis. According to the literature, reported cases of Masson tumor occur in skin and subcutaneous tissue of fingers, head and neck, trunk, and lower and upper extremities, in order of decreasing frequency. Similar cases rarely occur in the solid organs of the abdominal cavity. 2–9 We report a case of serious renal hemorrhage in a patient with Masson tumor, chronic kidney failure being treated with hemodialysis, and serious arterial hypertension after kidney transplantectomy because of ter- minal chronic allograft nephropathy. We diagnosed IPEH after a left nephrectomy performed because of serious acute anemia due to breach of the left native kidney. An emergency non– contrast enhanced abdominal computed tomographic (CT) scan showed massive retroperitoneal hemorrhage. At histologic analysis, the lesion had several important distinguishing characteristics that were helpful in confirming the diagnosis of IPEH. CASE REPORT A 49-year-old white man with terminal chronic allograft nephrop- athy being treated with hemodialysis was referred because of continous parainguinal pain, oliguria, hematuria, and increasing volume of the transplanted kidney. We performed an intracapsular transplantectomy. Histologic analysis confirmed chronic allograft nephropathy with the presence of an acute rejection episode. From the Kidney Transplant Unit (V.R., P.D.C., C.M., A.F., F.P.), Department of Surgery, and the Pathological Anatomy and Histology Unit (G.C.), San Salvatore Hospital, University of L’Aquila, L’Aquila, Italy. Address reprint requests to Vinicio Rizza, MD, University of L’Aquila Transplant Unit, San Salvatore Hospital, Via Vetoio, 67100 L’Aquila, Italy. E-mail: vinicio1979@interfree.it 0041-1345/09/$–see front matter © 2009 by Elsevier Inc. All rights reserved. doi:10.1016/j.transproceed.2009.03.010 360 Park Avenue South, New York, NY 10010-1710 1402 Transplantation Proceedings, 41, 1402–1404 (2009)