(also known as nephroblastoma)
Wilms tumor is a type of childhood cancer that starts in the kidneys. It is the most common type of kidney cancer in children, accounting for about 9 out of 10 cases of pediatric kidney cancer.
Wilms tumor most commonly affects children ages 3 to 4 with the rate of occurrence dropping off drastically after age 5. Wilms tumors are typically unilateral, most often found only in one kidney, though there have been cases of both kidneys being affected.