Clear cell sarcoma of kidney (CCSK) is a malignant renal tumor of childhood with a peak incidence in the 2nd year of life. It makes up about 5% of pediatric renal tumors. There is slight male predominance. Grossly, the tumor is usually solitary, large, and centered around renal medulla. It is well-demarcated from the normal kidney, and has tan-grey, soft surface. Cystic foci and areas of hemorrhage and necrosis may be found. Image courtesy of Dr. Jean-Christophe Fournet, Paris, France; humpath.com; Used with permission.