Wilms tumor, also known as nephroblastoma, is a rare type of kidney cancer that primarily affects children. It typically presents as a solid tumor in one or both kidneys and is the most common primary malignant renal tumor in pediatric patients. What is Wilms tumor and how does it affect the body? Wilms tumor arises from immature kidney cells (metanephric blastema) that fail to differentiate properly during fetal development. These cells continue to grow after birth, forming a mass that can displace healthy kidney tissue. While it primarily affects the renal system, if left untreated, Wilms tumor can metastasize, most commonly spreading to the lungs, liver, or lymph nodes. Who is typically affected by Wilms tumor? Wilms tumor is primarily a pediatric diagnosis, with the median age of onset being approximately 3 to 4 years old. It is rarely seen in children over the age of 8 or in adults. According to the NIH, it affects approximately 1 in 10,000 children worldwide. While there is no significant difference in incidence between genders, it is slightly more prevalent in African American children compared to Caucasian children. What are the key characteristics of Wilms tumor? The clinical presentation and management of Wilms tumor are defined by specific pathological features. Key diagnostic and classification facts include: Unilateral vs. Bilateral: About 90% of cases are unilateral (affecting one kidney), while 5-10% are bilateral (affecting both). Histological Subtypes: It is broadly classified into "favorable" and "unfavorable" (anaplastic) histology, which helps determine the intensity of the treatment plan. Genetic Associations: While most cases are sporadic, Wilms tumor is associated with certain genetic syndromes, such as WAGR syndrome, Denys-Drash syndrome, and Beckwith-Wiedemann syndrome. DiseaseMaps Community: Our community currently includes 18 people who have shared their personal experiences with Wilms tumor, providing a space for families to connect. Next steps Consult a pediatric oncologist or a pediatric urologist for a formal evaluation and diagnostic imaging (such as an ultrasound or CT scan). Discuss genetic counseling with your medical team if there is a family history of renal abnormalities. Join the DiseaseMaps.org community to connect with others who have navigated a Wilms tumor diagnosis. Medical disclaimer: This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the advice of your physician or qualified health provider with any questions regarding a medical condition. References National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD) Orphanet: Portal for rare diseases and orphan drugs Online Mendelian Inheritance in Man (OMIM) National Cancer Institute (NCI) Pediatric Renal Tumors Treatment (PDQ)

Short answer · Medically reviewed summary · Last updated: 2026-05-08

Wilms tumor, also known as nephroblastoma, is a rare type of kidney cancer that primarily affects children. It typically presents as a solid tumor in one or both kidneys and is the most common primary malignant renal tumor in pediatric patients. What is Wilms tumor and how does it affect the body? Wilms tumor arises from immature kidney cells (metanephric blastema) that fail to differentiate properly during fetal development.

What is Wilms Tumor

Name: What is Wilms Tumor
Creator: DiseaseMaps Editorial Team
Published: 2015-12-30UTC22:23:56.0000000

What is Wilms Tumor? Plain-language, medically reviewed definition plus the lived reality told by patients.

Wilms tumor, also known as nephroblastoma, is a rare type of kidney cancer that primarily affects children. It typically presents as a solid tumor in one or both kidneys and is the most common primary malignant renal tumor in pediatric patients.

What is Wilms tumor and how does it affect the body?

Wilms tumor arises from immature kidney cells (metanephric blastema) that fail to differentiate properly during fetal development. These cells continue to grow after birth, forming a mass that can displace healthy kidney tissue. While it primarily affects the renal system, if left untreated, Wilms tumor can metastasize, most commonly spreading to the lungs, liver, or lymph nodes.

Who is typically affected by Wilms tumor?

Wilms tumor is primarily a pediatric diagnosis, with the median age of onset being approximately 3 to 4 years old. It is rarely seen in children over the age of 8 or in adults. According to the NIH, it affects approximately 1 in 10,000 children worldwide. While there is no significant difference in incidence between genders, it is slightly more prevalent in African American children compared to Caucasian children.

What are the key characteristics of Wilms tumor?

The clinical presentation and management of Wilms tumor are defined by specific pathological features. Key diagnostic and classification facts include:

Unilateral vs. Bilateral: About 90% of cases are unilateral (affecting one kidney), while 5-10% are bilateral (affecting both).

Histological Subtypes: It is broadly classified into "favorable" and "unfavorable" (anaplastic) histology, which helps determine the intensity of the treatment plan.

Genetic Associations: While most cases are sporadic, Wilms tumor is associated with certain genetic syndromes, such as WAGR syndrome, Denys-Drash syndrome, and Beckwith-Wiedemann syndrome.

DiseaseMaps Community: Our community currently includes 18 people who have shared their personal experiences with Wilms tumor, providing a space for families to connect.

Next steps

Consult a pediatric oncologist or a pediatric urologist for a formal evaluation and diagnostic imaging (such as an ultrasound or CT scan).

Discuss genetic counseling with your medical team if there is a family history of renal abnormalities.

Join the DiseaseMaps.org community to connect with others who have navigated a Wilms tumor diagnosis.

Medical disclaimer: This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the advice of your physician or qualified health provider with any questions regarding a medical condition.