The revised International Society of Paediatric Oncology (SIOP) working classification of renal tumours of childhood (2001)
| I Low risk tumours |
Mesoblastic nephroma |
Cystic partially differentiated nephroblastoma |
Nephroblastoma—completely necrotic (following preoperative chemotherapy) |
| II Intermediate risk tumours |
Nephroblastoma—epithelial type |
Nephroblastoma—stromal type |
Nephroblastoma—mixed type |
Nephroblastoma—regressive type |
Nephroblastoma—focal anaplasia type |
| III High risk tumours |
Nephroblastoma—blastemal type |
Nephroblastoma—diffuse anaplasia type |
Clear cell sarcoma of the kidney |
Rhabdoid tumour of the kidney |