Table 1.

INSS classifications [6]

Stage	Definition
1	Localised tumour with complete gross excision; ipsilateral lymph nodes negative for tumour unless attached to and removed with the primary tumour
2	Localised tumour with incomplete gross excision, or localised tumour with nonadherent ipsilateral lymph nodes positive for tumour
3	Unresectable unilateral tumour infiltrating across the midline with or without regional lymph nodes positive for tumour; localised unilateral tumour with contralateral regional lymph nodes positive for tumour; or midline tumour with bilateral unresectable infiltration or bilateral lymph nodes positive for tumour
4	Any primary tumour with distant metastatic dissemination (except stage 4S)
4S	Localised primary tumour with metastatic dissemination limited to skin, liver, and/or bone marrow* in patients younger than 12 months

^*Bone marrow involvement must be less than 10% at biopsy, and bone marrow must be negative on MIBG studies.