Wilms Tumor Workup

Updated: May 21, 2020
  • Author: Arnold C Paulino, MD; Chief Editor: Jennifer Reikes Willert, MD  more...
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Approach Considerations

The following studies are indicated in patients with Wilms tumor:

  • Complete blood count (CBC)

  • Chemistry profile - Including kidney function tests and routine measurements of electrolytes and calcium

  • Urinalysis

  • Coagulation studies

  • Cytogenetics studies, including 1p and 16q deletion

Results may reveal an 11p13 deletion, as in WAGR syndrome, or a duplication of the paternal allele 11p15, as in Beckwith-Wiedemann syndrome (BWS). Mutational analysis of the WT1 gene may be indicated when Denys-Drash syndrome (intersexual disorders, nephropathy, Wilms tumor) is suspected.


Imaging Studies

Four-field chest radiography

Images may depict lung metastases. Patients with lung lesions on chest radiography have traditionally been given whole-lung radiation therapy.

Renal ultrasonography

Renal ultrasonography is often the initial study, because it does not expose children to the detrimental effects of radiation. Real-time ultrasonography is a relatively inexpensive way of helping determine the patency of the inferior vena cava. When a tumor is identified in the vessel, the proximal extent of the thrombus must be established prior to surgery, because of possible extension of the tumor to the right atrium.

CT scanning

Abdominal computed tomography (CT) scanning helps in determining the origin of the tumor, involvement of the lymph nodes, bilateral kidney involvement, invasion into major vessels (eg, inferior vena cava), and liver metastases. [25] See the images below.

CT scan in a patient with a right-sided Wilms tumo CT scan in a patient with a right-sided Wilms tumor with favorable histology.
CT scan of child with a stage IV Wilms tumor with CT scan of child with a stage IV Wilms tumor with favorable histology. Note the bilateral pulmonary metastases.

If chest CT scan findings are positive and chest radiographic findings are negative, diagnostic biopsy of the lesions noted on the chest CT scan is recommended.

MRI scanning

Abdominal magnetic resonance imaging (MRI) is reportedly the most sensitive imaging modality for determination of caval patency and may be important in determining whether the inferior vena cava is directly invaded by the tumor. Wilms tumor demonstrates low signal intensity on T1-weighted images and high signal intensity on T2-weighted images.


Surgical Examination and Biopsy

Histopathologic confirmation of Wilms tumor is essential. In North America, patients with suspected Wilms tumor undergo nephrectomy immediately (see the image below). During this procedure, the contralateral kidney is explored to ensure that the disease is indeed unilateral, and lymph node biopsy samples are obtained for staging purposes. Lymph node dissection is not indicated. (Immediate nephrectomy is not performed in patients with bilateral disease at presentation, when sparing of the renal tissue becomes important.)

Gross nephrectomy specimen shows a Wilms tumor pus Gross nephrectomy specimen shows a Wilms tumor pushing the normal renal parenchyma to the side.

In contrast to immediate surgery, most European centers make a presumptive diagnosis of Wilms tumor based on imaging findings alone. Clinicians in Europe prefer to administer chemotherapy before nephrectomy without survival compromise. [26, 27]

Transcutaneous biopsy is not usually recommended and may in fact complicate treatment by causing preoperative tumor spill, requiring whole abdominal radiotherapy.


Histologic Findings

The classic histologic pattern in Wilms tumor is triphasic and composed of epithelial, blastemal, and stromal elements. Approximately 90% of all renal tumors have favorable histology.

About 3-7% of Wilms tumors are characterized by anaplastic changes. If these changes are present diffusely throughout the tumor, they are predictive of a poor outcome. Wilms tumors with anaplastic changes have unfavorable histology.

Two tumor types previously included in the category with unfavorable histology are, in fact, clearly separate malignant entities: clear cell sarcoma of the kidney and rhabdoid tumor of the kidney.

The improved histopathologic classification of childhood renal tumors has not only helped to define appropriate treatment strategies for these patients but has also contributed to the understanding of the molecular genetic events underlying the Wilms tumor.

For instance, nephrogenic rests, dysplastic lesions of metanephric origin, are now believed to represent precursor lesions. These lesions are observed in approximately one third of kidneys affected by Wilms tumors.

The relationship between the pathology of the nephrogenic rests, the tumor, and the congenital disorders is of particular interest. These associations have been helpful in evaluating a potential correlation between a Wilms tumor phenotype in one regard and molecular genetic events leading to the development of that same tumor in another.

Children younger than age 12 months diagnosed with perilobar nephrogenic rests have a markedly increased risk of developing a contralateral Wilms tumor. [28]