[citation needed] The mesenchymal component may include cells showing rhabdomyoid differentiation or malignancy (rhabdomyosarcomatous Wilms).

[citation needed] Wilms' tumors may be separated into two prognostic groups based on pathologic characteristics:[citation needed] Mutations of the WT1 gene which is located on the short arm of chromosome 11 (11p13) are observed in approximately 20% of Wilms' tumors, the majority of them being inherited from the germline, while a minority are acquired somatic mutations.

The majority of people with Wilms' tumor present with an asymptomatic abdominal mass which is noticed by a family member or healthcare professional.

[22][23] According to the extent of tumor tissue at the time of initial diagnosis, four stages are considered, with a fifth classification for bilateral involvement.

[citation needed] 5% of Wilms' tumor cases at the time of initial diagnosis are bilateral involvements, which pose unique challenges to treatment.

Tumor-specific loss-of-heterozygosity (LOH) for chromosomes 1p and 16q identifies a subset of Wilms' tumor patients who have a significantly increased risk of relapse and death.

[26][27] Genome-wide copy number and LOH status can be assessed with virtual karyotyping of tumor cells (fresh or paraffin-embedded).

[citation needed] In case of relapse of Wilms' tumor, the 4-year survival rate for children with a standard-risk has been estimated to be 80%.

[33] A genetic predisposition to Wilms' tumor in individuals with aniridia has been established, due to deletions in the p13 band on chromosome 11.

By employing the antibiotic actinomycin D in addition to surgery and radiation therapy, they boosted cure rates from 40 to 89 percent.

[35] The use of computed tomography scan for the diagnosis of Wilms' tumor began in the early 1970s, thanks to the intuition of Mario Costici, an Italian physician.

He discovered that in the direct radiograms and in the urographic images, determining elements for a differential diagnosis with the Wilms' tumor can be identified.