Wilms tumour of the kidney

a) The tumour is limited to kidney or surrounded with a fibrous pseudocapsule if outside of the normal contours of the kidney. The renal capsule or pseudocapsule may be infiltrated with the tumour but it does not reach the outer surface, and it is completely resected (resection margins ‘clear’)

b) The tumour may be protruding (‘bulging’) into the pelvic system and ‘dipping’ into the ureter (but it is not infiltrating their walls)

c) The vessels of the renal sinus are not involved

d) Intra renal vessel involvement may be present

Fine needle aspiration or percutaneous core needle biopsy (‘tru-cut’) does not upstage the tumour.

a) The tumour extends beyond kidney or penetrates through the renal capsule and/or fibrous pseudocapsule into peri-renal fat but is completely resected (resection margins ‘clear’)

b) Tumour infiltrates the renal sinus and/or invades blood and lymphatic vessels outside the renal parenchyma but it is completely resected

c) Tumour infiltrates adjacent organs or vena cava but is completely resected

a) Incomplete excision of the tumour which extends beyond resection margins (gross or microscopic tumour remains post-operatively)

b) Any abdominal lymph nodes are involved

c) Tumour rupture before or intra-operatively (irrespective of other criteria for staging)

d) The tumour has penetrated through the peritoneal surface

e) Tumour implants are found on the peritoneal surface

f) The tumour thrombi present at resection margins of vessels or ureter, transected or removed piecemeal by surgeon

g) The tumour has been surgically biopsied (wedge biopsy) prior to pre-operative chemotherapy or surgery.

The presence of necrotic tumour or chemotherapy-induced changes in a lymph node or at the resection margins is regarded as proof of previous tumour with microscopic residue and therefore the tumour is assigned stage III (because of the possibility that some viable tumour is left behind in the adjacent lymph node or beyond resection margins.)

Haematogeneous metastases (lung, liver, bone, brain, etc.) or lymph node metastases outside the abdomino-pelvic region.

Bilateral renal tumours at diagnosis. Each side should be sub staged according to above classifications.