Definition of Wilms’s Tumor

Wilms’s Tumor – a malignant (cancerous) growth in the kidney. Wilms’s tumor, also called nephroblastoma, nearly always affects children under age six.

Though relatively rare, with doctors diagnosing about 500 children a year in the United States with this form of kidney cancer, Wilms’s tumor is the most common cancer of the kidney that occurs in children.

Current treatment approaches have much improved survival, with the five-year survival rate now exceeding 90 percent.

STAGING OF WILMS’S TUMOR
Wilms’s Tumor StageExtent of CancerTreatment Protocols/Options
stage 1tumor is small and remains localized in one kidneypartial or simple NEPHRECTOMY followed by CHEMOTHERAPY
stage 2tumor extends beyond the kidney though remains confined to a single mass that surgery can completely removeradical nephrectomy followed by chemotherapy
stage 3tumor extends to adjacent structures and lymph nodes and surgery cannot completely remove itchemotherapy before surgery
radical nephrectomy followed by chemotherapy and possibly RADIATION THERAPY
stage 4tumor has metastasized to distant siteschemotherapy
nephrectomy
radiation therapy
stage 5both KIDNEYS have tumorspartial nephrectomy of both kidneys to remove as much cancer as possible yet retain kidney function
chemotherapy
repeat partial nephrectomy
radiation therapy
inoperabletumor is very large or located too close to vital blood vessels for surgery to be viablechemotherapy, radiation therapy, or a combination to reduce the tumor’s size

Symptoms and Diagnostic Path

Wilms’s tumor may not show symptoms until it is quite large, at which point a parent or caregiver may see or feel the tumor as a lump in the child’s belly. The pediatrician may discover Wilms’s tumor during a routine well-child examination. When the tumor causes symptoms, they often include

  • HEMATURIA (bloody URINE)
  • decreased APPETITE and weight loss
  • NAUSEA and VOMITING
  • abdominal discomfort or PAIN
  • generalized irritability and crankiness

The diagnostic path begins with a comprehensive physical examination, blood tests, and urinalysis. Diagnostic imaging procedures such as ultrasound, computed tomography (CT) scan, or magnetic resonance imaging (MRI) can identify the presence, size, and location of the tumor. Biopsy of the tumor is necessary to confirm the diagnosis.

Microscopic examination of the biopsied tissue further allows the pathologist to determine whether the tumor’s cells are anaplastic, which means they are highly irregular and divide both rapidly and erratically. Tumors of anaplastic cells may be diffuse through the kidney and are more difficult to treat than tumors of what pathologists call favorable cells (cancerous cells that are more pathologically normal). The pathologist also assigns the cancer a grade that identifies the extent to which the tumor has spread (metastasized), which helps determine the appropriate treatment options.

Treatment Options and Outlook

NEPHRECTOMY (surgery to remove the affected kidney) in combination with CHEMOTHERAPY is the standard treatment for Wilms’s tumor cancers. Partial nephrectomy removes the tumor and a margin of kidney tissue around it; simple nephrectomy removes the entire kidney. Radical nephrectomy removes the kidney. The oncologist may also add RADIATION THERAPY when the cancer’s stage is advanced or its cells are anaplastic regardless of stage.

When the tumor is very large or the cancer involves both KIDNEYS, the oncologist may recommend chemotherapy or radiation therapy (or a combination of both) before surgery to shrink the tumors as much as possible. The oncologist may suggest participation in a clinical trial for inoperable, stage 5, or recurrent Wilms’s tumor.

Treatment success largely correlates to the stage of the Wilms’s tumor (the size of the tumor and the extent to which it has metastasized) and the characteristics of the cancer cells (anaplastic or favorable) at the time of diagnosis.

Wilms’s tumor is among the childhood cancers doctors consider curable.

Risk Factors and Preventive Measures

Researchers have recently identified GENE mutations that account about 30 percent of Wilms’s tumor cancers. Located on CHROMOSOME 11, these are the Wilms’s tumor 1 (WT1) and 2 (WT2) genes and provide encoding for development of urinary and genital structures. Wilms’s tumor also is associated with several rare genetic syndromes, making it likely that other gene mutations further contribute to the errant encoding that allows these primitive cells to thrive. Family history raises the risk for Wilms’s tumor, as it appears the gene mutations are sometimes hereditary.

Researchers believe Wilms’s tumor represents clusters of cells in the kidneys that remain primitive, a consequence of the WT1 and WT2 mutations. When these primitive cells divide, they continue to do so at the same rapid rate of cell division that was normal in the EMBRYO. In the older child’s body, however, this is inappropriate and the cells grow out of control, some wildly (the anaplastic cells).

Some researchers believe the cell growth continues from early developmental stages and ultimately manifests as a tumor when the cluster of cells achieves enough mass. Other researchers believe environmental factors, perhaps processes in the body related to growth, trigger the cells to resume dividing.

There are no measures to prevent Wilms’s tumor. Families who have had children with Wilms’s tumor should have any other children undergo staregular routine medical examinations that include screening (such as ultrasound) for the cancer.

Doctors do not yet know the long-term health implications for Wilms’s tumor survivors as the treatments that make survival possible have not been available long enough for many survivors to have yet reached adulthood.

See also BLADDER CANCERCANCER TREATMENT OPTIONS AND DECISIONS; MUTATIONRENAL CANCERSURGERY BENEFIT AND RISK ASSESSMENT.

Wilms’s Tumor – Symptoms, Treatment and Prognosis
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