Wilms tumor usually manifests in children < 5 year of age but occasionally in older children and rarely in adults. Wilms tumor accounts for about 6% of cancers in children< 15 years of age. 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 2nd Wilms tumor suppressor gene), loss of heterozygosity 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.
Abdominal ultrasonography 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 Stages of Wilms Tumor).
Prognosis for Wilms tumor depends on
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.
Initial treatment of unilateral Wilms tumor is primary surgical resection followed by adjuvant chemotherapy. A select group of younger patients with small tumors can be cured by surgery alone. The type of chemotherapy drug and the length of therapy depends on tumor histology and stage. The chemotherapy regimen depends on the risk group but usually consists of actinomycin D (dactinomycin) and vincristine with or without doxorubicin. For more aggressive tumors, intensive multiagent chemotherapy regimens are used.
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.