Wilms tumor is an embryonal cancer of the kidney composed of blastemal, stromal, and epithelial elements. Genetic abnormalities have been implicated in the pathogenesis, but familial inheritance accounts for only 1 to 2% of cases. Diagnosis is by ultrasonography, abdominal CT, or MRI. Treatment may include surgical resection, chemotherapy, and radiation therapy.
Wilms tumor usually manifests in children < 5 years of age but occasionally in older children and rarely in adults. Wilms tumor accounts for about 4% of cancers in children < 15 years of age (1). Bilateral synchronous tumors occur in about 5% of patients.
A chromosomal deletion of WT1 (a Wilms tumor suppressor gene) has been identified in some cases. Other associated genetic abnormalities include deletion of WT2 (a second Wilms tumor suppressor gene), loss of heterozygosity (LOH) of 16q and 1p, and inactivation of the WTX gene.
About 10% of cases manifest with other congenital abnormalities, especially genitourinary abnormalities, but also hemihypertrophy (asymmetry of the body). WAGR syndrome is the combination of Wilms tumor (with WT1 deletion), aniridia, genitourinary malformations (eg, renal hypoplasia, cystic disease, hypospadias, cryptorchidism), and intellectual disablity.
Reference
1. Louis DN, Perry A, Wesseling P, et al: The 2021 WHO classification of tumors of the central nervous system: A summary. Neuro Oncol 23(8):1231–1251, 2021. doi: 10.1093/neuonc/noab106
Symptoms and Signs of Wilms Tumor
The most frequent finding is a painless, palpable abdominal mass.
Less frequent findings include abdominal pain, hematuria, fever, anorexia, nausea, and vomiting. Hematuria can be microscopic or gross.
Hypertension may occur and is of variable severity.
Diagnosis of Wilms Tumor
Abdominal ultrasonography, CT, or MRI
Abdominal ultrasonography with Doppler determines whether the mass is cystic or solid and whether the renal vein or vena cava is involved. Abdominal CT or MRI is needed to determine the extent of the tumor and check for spread to regional lymph nodes, the contralateral kidney, or liver.
Chest CT is recommended to detect metastatic pulmonary involvement at initial diagnosis.
Diagnosis of Wilms tumor is typically made presumptively based on the results of the imaging studies, so nephrectomy rather than biopsy is done in most patients at the time of diagnosis. Biopsy is not done because of the risk of peritoneal contamination by tumor cells, which would spread the cancer and thus change the stage from a lower to a higher one, requiring more intensive therapy.
During surgery, locoregional lymph nodes are sampled for pathologic and surgical staging (see also the National Cancer Institute's Diagnostic and Staging Evaluation for Wilms Tumor).
Treatment of Wilms Tumor
Surgery and chemotherapy
Radiation therapy for patients with higher stage/risk disease
(See also the National Cancer Institute's Treatment of Wilms Tumor.)
The initial treatment approach to unilateral Wilms tumor can vary by country or region. Most clinical trials for treatment of children with Wilms tumor have been conducted by the Children's Oncology Group (COG) in the US and by the International Society for Paediatric Oncology (SIOP) in Europe. In the COG treatment protocol, resection of all unilateral tumors is done first, whereas in the SIOP treatment protocol, preoperative chemotherapy is done first. Both groups recommend postoperative chemotherapy except in select cases.
Radiation therapy is used to improve local control in certain cases depending on risk stratification as well as to treat metastatic sites of disease.
Although rare, a select group of younger patients (< 2 years of age) with small tumors (< 550 g) and stage 1 favorable histology can be cured by surgery alone (1).
Children with very large, nonresectable tumors or bilateral tumors are candidates for chemotherapy followed by reevaluation and delayed resection.
Children who have higher-stage disease or tumors involving the regional lymph nodes are given radiation therapy.
Treatment reference
1. Green DM, Breslow NE, Beckwith JB, et al: Treatment with nephrectomy only for small, stage I/favorable histology Wilms' tumor: A report from the National Wilms' Tumor Study Group. J Clin Oncol 19(17):3719–3724, 2001. doi: 10.1200/JCO.2001.19.17.3719
Prognosis for Wilms Tumor
Prognosis for Wilms tumor depends on
Histology (favorable or unfavorable)
Stage at diagnosis
Patient’s age (older age is associated with a worse prognosis)
Molecular findings (loss of heterozygosity at 1p, 11p15, and 16q, and 1q gain are associated with increased relapse)
The outcome for children with Wilms tumor is excellent. Cure rates for lower-stage disease (localized to the kidney) range from 85% to 95%. Even children with more advanced disease fare well; cure rates range from 60% (unfavorable histology) to 90% (favorable histology).
The cancer may recur, typically within 2 years of diagnosis. Cure is possible in children with recurrent cancer. Outcome after recurrence is better for children who present initially with lower-stage disease, whose tumors recur at a site that has not been irradiated, who relapse > 1 year after presentation, and who receive less intensive treatment initially.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Cancer Institute (NCI): Diagnostic and Staging Evaluation for Wilms Tumor
