Table 1.

Wilms tumor stages according to the Children’s Oncology Group.

Stage	Criteria
Stage I	Confined to kidney
	Complete excision with renal capsule intact and negative resection margins
	Lymph nodes negative for Wilms tumor spread
Stage II	Regional extension beyond kidney capsule, but confined to flank
	May include:
	Tumor penetration through capsule but confined to Gerota’s fascia
	Infiltration into renal vein
	Complete excision with negative resection margins
	Lymph nodes negative for Wilms tumor spread
Stage III	Residual tumor, but confined to abdomen
	May include:
	Regional lymph node involvement
	Peritoneal contamination:
	Biopsy
	Pre- or intraoperative tumor rupture
	Tumor growth through peritoneal surface
	Positive resection margins
Stage IV	Distant metastases: Lung, liver, bone, brain
Stage V	Involvement of bilateral kidneys at diagnosis

Adapted from Davidoff (2012) [4].