Nephroblastoma, light micrograph. Nephroblastoma, or Wilms tumour, is the fourth most common type of childhood cancer and the most common type of kidney cancer in children. The peak incidence is seen between 2 and 5 years of age. It is only rarely seen as a congenital neoplasm. They are usually solitary, large, and sharply demarcated tumours. About 7% are multicentric and 5% of cases are bilateral. Some of the current treatment protocols for Wilms tumour call for preoperative chemotherapy followed by resection. The post-chemotherapy tumours are evaluated for response and subdivided into 3 risk categories : low risk, intermediate risk, and high risk. This image shows a few residual tubules surrounded by a zone of fibrosis and haemorrhage with scattered inflammatory cells.