The tumor was biopsied or there was local spillage of tumor confined to the flank. Stage III Wilms' is defined as residual tumor confined to the abdomen. Lymph nodes in the renal hilus, the periaortic chains, or beyond are found to contain tumor on biopsy. There has been diffuse peritoneal contamination by the tumor, such as by spillage of tumor beyond the flank before or during surgery or by tumor growth that has penetrated through the peritoneal surface. Implants are found on the peritoneal surfaces.
Tumor extends beyond the surgical margins either microscopically or grossly.
Tumor is not completely resectable because of local infiltration into vital structures. Stage IV Wilms' tumor is defined as the presence of hematogenous metastases. There are metastatic deposits beyond stage III, e.g., to the lung, liver, bone, or brain or to a combination of these sites. Stage V Wilms' tumor is defined as bilateral renal involvement at the time of initial diagnosis. For patients with bilateral involvement, an attempt should be made to stage each side according to the above criteria on the basis of extent of disease prior to biopsy.