Wilms tumour

Wilms tumour, also known as nephroblastoma, is a malignant paediatric renal tumour.

Wilms tumours are the most common paediatic renal mass, accounting for over 85% of cases 1,8 and accounts for 6% of all childhood cancers 2. It typically occurs in early childhood (1-11 years) with peak incidence between 3 and 4 years of age. Approximately 80% of these tumours are found before the age of 5 years. When part of a syndrome (see below) they occur even earlier, typically between 2 and 24 months of age 1.

There is no recognised gender predilection, however, presentation is a little later in females 2. The vast majority are unilateral with less than 5 % occurring bilaterally.

Clinical presentation is typically with a painless upper quadrant abdominal mass. Hematuria is seen in ~20% of cases 2 and pain is uncommon. On examination hypertension due to excessive renin production is found in up to 25% of patients 1 and acquired von Willebrand disease is seen in 8% 2

Although most cases are sporadic and only 2% of cases are familial, a number of associations are recognised 1, 2:

The tumour typically arises from mesodermal precursors of the renal parenchyma (metanephros). Increasingly gene loci are being implicated on chromosome 11 (WT1: 11p13 and WT2: 11p15) as well as WTX on chromosome X, B-catenin on chromosome 3 or TP53 on chromosome 17 1.

On gross inspection, these tumours are usually well circumscribed or macrolobulated. Haemorrhage and central necrosis are common findings 10

Wilms tumours are usually large heterogeneous solid masses which displace adjacent structures. Occasionally they may be mostly cystic. 

Metastases are most commonly to lung (85%), liver and local lymph nodes 1. Similar to renal cell carcinoma tumour thrombus into the renal vein, IVC and right atrium are also characteristic of advanced disease. See also: Wilms tumour staging.

Abdominal x-ray typically reveals a large soft tissue opacity displacing bowel. This is only relevant if found incidentally since a radiograph should never be used for the assessment of an abdominal mass. The only exception would be a resource-poor setting where an abdominal radiograph is the only imaging modality available.

Ultrasound is a very useful examination and in almost every situation will be the primary investigation of choice. It is helpful to localise the mass to kidney and also distinguish from other causes of renal masses (e.g. hydronephrosis). Although many of the features seen on CT/MRI can also be identified on US, the former are required to adequately stage the disease, and is established in protocols for Wilms tumour staging in North America and Europe 9 .

Doppler examination can be performed to examine the renal vein and IVC to assess for the presence of tumour thrombus.

Wilms tumours are heterogeneous soft-tissue density masses with infrequent areas of calcification (~15%) 10 and fat-density regions. Enhancement is also patchy, and allows for better delineation of the relationship between the mass and kidney. 20% of cases have lung metastases at time of diagnosis.

Where MRI is available it is the investigation of choice for staging since it does not involve ionising radiation. It is also the most accurate modality in assessing for IVC involvement 1 where protocols have been optimised. These tumours appear heterogeneous on all sequences and frequently contain blood products. 

  • T1: hypointense
  • T1 C+ (Gd): heterogeneous enhancement
  • T2: hyperintense

Bone scans are not routine as the tumour metastasizes to bones very late. F-18 FDG PET/CT is increasingly used as a problem solving tool and to distinguish scar tissue from residual active tumour.

Unilateral Wilms tumours are, usually, treated by a combination of nephrectomy and chemotherapy. Occasionally chemotherapy can be administered prior to surgery to downstage the tumour 1. This is especially useful when tumours are bilateral.

Radiotherapy has a limited role, but may be employed in cases of peritoneal spread or incomplete resection 1.

Cure is now possible in ~90% of cases. Recurrence is seen both within the tumour bed, as well as distally within the lungs or liver 1-2.

This entity was popularised by Max Wilms in 1899, although prior descriptions had been published by Osler in 1814 and Birch-Hirschfeld in 1879 3-5.

  • Max Wilms (1867-1918), surgeon; Heidelberg, Germany 3
  • Felix Victor Bisch-Hirschfeld (1842-1899), physician; Leipzig, Germany 6
  • William Osler (1849-1919), physician; Montreal, Canada 7

General imaging differential considerations include:

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Article information

rID: 8152
Synonyms or Alternate Spellings:
  • Wilm's tumour
  • Wilms tumours
  • Nephroblastoma
  • Wilms' tumour
  • Wilms tumour
  • Wilms tumors
  • Embryoma of kidney

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    Case 8: bilateral Wilms tumours (nephroblastoma)
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