Also known as nephroblastoma, Wilms tumor is the most common type of kidney cancer found in pediatric groups. The peak incidence of this disease is found to be between ages 2 to 5 years old. Wilms tumor can involve both kidneys either at the same time or in succession. The tumor can be classified according to its histomorphology – favorable histology or anaplastic histology.

The exact cause of Wilms tumor is unclear however, genetic alterations to the normal embryological development of the genitourinary tract is thought to be associated with its etiology. The risk for developing Wilms tumor is increased with at least three types of syndromes and congenital malformations with distinct chromosomal origins. 

1. WAGR syndrome is characterized by Wilms tumor, aniridia (complete or partial absence of the iris of the eye), genitourinary anomalies, and intellectual disability. The risk of Wilms tumor in patients with WAGR syndrome is around 33%. This syndrome is caused by deletions of the WT1 gene located at the 11p13 chromosome leading to reduced amounts of proteins needed for gonadal and renal development.
2. Denys-Drash syndrome has a higher risk for developing Wilms tumor at 90%. This syndrome is caused by a missense mutation of the WT1, rather than a deletion as seen in WAGR syndrome, which may alter the function of the protein made from the gene. Patients with Denys-Drash syndrome present with gonadal dysgenesis (male pseudohermaphroditism) and early-onset nephropathy as well as diffuse mesangial sclerosis lesion in the glomerulus.
3. Beckwith-Wiedemann syndrome (BWS) is an overgrowth disorder caused by microduplication mutations in the 11p15.5 region (so-called WT2 locus), found distal to the WT1 locus. BWS is clinically diagnosed by the presence of organomegaly, macroglossia, hemihypertrophy, omphalocele, and abnormal large cells in the adrenal cortex.

Other congenital anomalies related to Wilms tumor include Perlman syndrome, Sotos syndrome, and Trisomy 18 among others.

Patients with Wilms tumor present with a large abdominal mass that may be unilateral or may extend into the pelvis when the tumor is very large. Other symptoms may be present, such as:

• Abdominal pain
• Hypertension
• Gross hematuria
• UTI
• Varicocele
• Fever
• Anemia
• Dyspnea or tachypnea may occur with lung metastases

Histologic confirmation is needed for the definitive diagnosis of nephroblastoma wherein three types of cells are found in the lesion- blastemal, stromal, and epithelial cell types. Abdominal imaging is taken to rule out other possible causes of abdominal mass found and to establish management approaches to treatment through surgery or chemotherapy. Chest imaging is also needed to determine possibilities of lung metastasis. Laboratory tests, such as CBC, renal function tests, coagulation studies, etc., may also be done to check for other pathologies.

The usual approach of treatment for Wilms tumor is nephrectomy followed by chemotherapy. Surgery for Wilms tumor may include partial removal of the affected region, radical nephrectomy wherein the affected kidney and its surrounding tissue is removed, and excision of both kidneys. The regimen of drugs used in chemotherapy include but is not limited to vincristine, dactinomycin, and doxorubicin. Radiation therapy may also be recommended based on the staging of the tumor.

There are no known environmental or lifestyle-related risks that cause Wilms tumor thus there is no specific way to prevent the tumor from occurring. High-risk patients, such as those with aforementioned syndromes can be screened. Children with Denys-Drash syndrome are recommended for early nephrectomy to prevent the development of tumors.

References:

Leslie SW, Sajjad H, Murphy PB. Wilms Tumor. [Updated 2022 May 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK442004/

Kumar, V., Abbas, A. K., & Aster, J. C. (2020). Robbins Basic Pathology (10th ed.). Elsevier – Health Sciences Division.

Smith V. and Chintagumpala M. (2022). Presentation, diagnosis, and staging of Wilms tumor. UptoDate. Retrieved from https://www.uptodate.com/contents/presentation-diagnosis-and-staging-of-wilms-tumor

Smith V. and Chintagumpala M. (2022). Treatment and prognosis of Wilms tumor. 

UptoDate. Retrieved from https://www.uptodate.com/contents/treatment-and-prognosis-of-wilms-tumor