Perirenal myelolipoma.

Extra-adrenal myelolipomas are rare, benign tumors composed of hematopoietic and adipose elements. Although these tumors can cause local symptoms or hemorrhage, they are generally asymptomatic. However, when discovered intraoperatively, they pose a diagnostic dilemma to the urologic surgeon. We present a case of perirenal extra-adrenal myelolipoma discovered intraoperatively in a patient with von Hippel-Lindau disease undergoing partial nephrectomy.