Wilms tumor, also known as nephroblastoma, is a cancer of the kidney that usually occurs in children younger than age 5. The causes are unknown, but it is believed that a genetic abnormality is involved in some cases. Wilms tumors arise from embryonal kidney tissues that have normally disappeared at the time of birth. The kidneys are a matched pair of organs about the size of a fist found on either side of the backbone. The kidneys filter and clean the blood, taking out unneeded products, and making urine.
Wilms Tumor occurs in about one in 12,000 children. It is the second most common solid tumor outside of brain tumors in children and makes up 7 percent of all childhood cancers. It is most often diagnosed between the ages of 6 months and 10 years, with the greatest number of children diagnosed by age 5. While there is evidence that some Wilms tumor children inherit a gene mutation that makes them more susceptible to the cancer, a recent study found that fewer than 10 percent of the cases can be attributed to the only identified gene linked to the cancer.