malignant renal (kidney) tumour of early childhood. In 75 percent of the cases, the tumour grows before the age of five; about two-thirds of the instances are apparent by two years of age. The tumour grows rapidly and can approach the weight of the rest of the body. It rarely appears in adults. In its early stages the nephroblastoma causes no symptoms. Later, symptoms may indicate fever, distortion of the kidney mass, evidence of secondary tumours elsewhere in the body, abdominal and flank pain, weight loss, nausea, loss of appetite, and vomiting.

The tumour begins in the outer (cortical) tissue of the kidney. At first it is surrounded by a dense fibrous capsule. It is usually a grayish-white, soft mass. The tumour tends to destroy the whole kidney and spreads to neighbouring organs. It often causes secondary tumours (metastases) in the lungs, liver, brain, and bones.

The usual treatment of a nephroblastoma, if diagnosis is early enough, is a course of radiation before an operation, removal of the mass by surgery, and postoperative irradiation. Sometimes chemicals are given to slow the cell growth.