Wilms' tumor is a type of kidney cancer that predominantly affects children. It usually occurs in the first five years of life, especially around ages three and four. In most cases, Wilms' tumor affects only one of the two kidneys. The frequency of this tumor is 1 in 200,000-250,000 children.
Wilms' tumor is generally divided into two types based on how it looks under the microscope. Favorable types of Wilms' tumor generally have a better outcome and require less aggressive treatment. The unfavorable or anaplastic histology of Wilms' Tumor is still curable, but requires more aggressive chemotherapy and higher doses of radiation therapy. Despite the more aggressive therapies, survival is generally more limited.
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In the fetus, some of the cells that are supposed to grow into mature kidneys stay as fetal kidney cells. Clusters of these cells sometimes remain after birth. If they do not mature within three or four years, they may grow out of control. A large mass of these cells forms and may develop into a Wilms' tumor.
A small percentage of children with Wilms' tumors have inherited an abnormal gene from one parent. This gene greatly increases the chance that some of their kidney cells will turn into a Wilms' tumor. Some other children have certain birth defects that increase their risk for Wilms' tumor. However, many children with Wilms' tumors do not have any known inherited gene changes or birth defects. Researchers do not know why these children have some kidney cells that do not mature properly.
A risk factor is something that increases your chance of getting a disease or condition. One risk factor for Wilms' tumor is having a family member with a Wilms' tumor. Also, certain birth defects increase the risk of a Wilms' tumor. These include:
The first noticeable symptom is usually a large lump or hard mass in the abdomen. Other symptoms may include:
Wilms' tumors may grow larger without causing any pain or other symptoms.
The doctor will ask about your child’s symptoms and medical history, and perform a physical exam. Blood and urine tests may be done.
Your child will need one or more of the tests below to look for tumors. These tests provide pictures of the kidney, surrounding blood vessels, and other organs to which the cancer may have spread:
Except for removal of the kidney, these tests are not invasive but require the child to remain still. Sedation may be needed.
Children who have risk factors for Wilms' tumor should have a physical exam with a specialist and an ultrasound every three months until age six or seven. This screening should be done even if they do not have symptoms. It can help find tumors while they are small and have not yet spread to other parts of the body.
Wilms' tumor can be cured in most children. The specific treatment depends on if the cancer has spread beyond the kidney to other parts of the body, and if so, how far. The process for determining this, called staging, uses the results of the diagnostic tests. Tumor size, cell type, whether the tumor is favorable or unfavorable, and your child’s age and health are also considered in choosing treatment.
In general, tumors with favorable histology are treated only with combinations of chemotherapy, and those with unfavorable patterns or which are recurrent, often require the addition of radiation therapy.
Treatment may include:
The main treatment for Wilms' tumor is a type of surgery called nephrectomy. This is the removal of the kidney with the tumor. The tissue around the kidney may also be removed, as well as some nearby lymph nodes. The remaining kidney will take care of all of the needed functions for the body.
Chemotherapy is the use of drugs to kill cancer cells. Chemotherapy can be given in many forms including: pill, injection, and via a catheter placed in a blood vessel. The drugs enter the bloodstream and travel through the body killing mostly cancer cells, but also some healthy cells.
This is the use of radiation to kill cancer cells and shrink tumors. Radiation may be:
Radiation of Tumor
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American Cancer Society
National Cancer Institute, National Institutes of Health (NIH)
Childhood Cancer Foundation
American Cancer Society website. Available at: http://www.cancer.org .
Driskoll K, Isakoff M, Ferrer F. Update on pediatric genitourinary oncology. Curr Opin Urol . 2007;17(4):281-286.
National Cancer Institute, National Institutes of Health (NIH) website. Available at: http://www.cancer.gov/ .
Pediatric Oncology Resource Center website. Available at: http://www.acor.org/ped-onc/ .
The United States National Library of Medicine, National Institutes of Health website. Available at: http://www.nlm.nih.gov/ .
Last reviewed September 2012 by Adrienne Carmack, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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