Wilms Tumor (Nephroblastoma)Nephroblastomas are usually solitary, large, and sharply demarcated tumors. The bulging cut surface is soft, fleshy, lobulated, yellow-tan, and frequently has areas of hemorrhage, necrosis, or cyst formation. About 7% are multicentric and 5% of cases are bilateral. Tumors with typical morphology of nephroblastoma have been documented in extra-renal sites. Image courtesy of Dr. Jean-Christophe Fournet, Paris, France; humpath.com; Used with permission.