Wilms' tumor is the most common type of kidney cancer affecting children. About one in every 10,000 children is affected by Wilms' tumor in the United States (Mar 23, 2018).
Wilms has a good survival rate if detected early but unfortunately many, like Wills, are not and some 10% do not respond to treatment as expected.
The Wilms foundation of North America's goal is to ensure we cure 100% of children diagnosed with Wilms Tumour.
Wilms’ tumours usually affect children under the age of five.
Most children affected with Wilms tumour have no clear underlying cause for their disease.
Several small studies have suggested that certain environmental factors may be associated with a higher risk of Wilms tumour, but the results were conflicting.
A few children are born with a genetic predisposition to Wilms tumour, such as children with the following factors:
Congenital abnormalities: It is well documented that certain syndromes are associated with Wilms tumour. The syndromes associated with the greatest risk of Wilms tumour are WAGR syndrome (Wilms tumour-aniridia-genitourinary malformation-retardation), Denys-Drash Syndrome, and Beckwith-Wiedemann Syndrome.
Familial Wilms tumour: Approximately 1.5 percent of children with Wilms tumour have a relative who was also affected with Wilms tumour.
Bilateral Wilms tumour: About 7 percent of patients with Wilms tumour have multiple tumours in one or both kidneys. Having multiple tumours does not indicate tumor spread.
Girls are at a slightly higher risk than boys of developing a Wilms' tumour.
The most common symptom of a Wilms’ tumour is a swollen stomach. This can occur quite suddenly and is usually painless to your child. Most Wilms' tumours are quite large when they are found. They are very often much bigger than the kidney itself. Fortunately, even though they are large, most of them have not spread to other parts of the body. Other less common symptoms include:
Bleeding inside the tumour causing pain
Blood in the urine – found in between 15 and 20 out of every 100 children (15 to 20%) with a Wilms' tumour
Raised blood pressure
High temperature (fever) and also regular low-grade fever (37.0-37.5)
Loss of appetite
Feeling or being sick
Shortness of breath and cough (only if the cancer has spread to the lungs)
Types of Wilms Tumors
There are 2 main types of Wilms’ tumour. The cells in each type look different under a microscope. Doctors call this the histology of the tumour. The 2 types are:
Wilms' tumour with favourable histology
Wilms' tumour with unfavourable histology
Unfavourable histology means that the cells look very large and not like normal kidney cells. The medical term for this is anaplasia. The cancer is less likely to be cured if there are lots of areas of anaplasia. But more than 9 out of 10 Wilms’ tumours (95%) have favourable histology. This means that there is no anaplasia and the chance of cure is high.
Several other very rare types of kidney cancers are found in children. Doctors used to group these as Wilms’ tumours with unfavourable histology but they are now grouped separately. They are treated in the same way as a Wilms' tumour but often more intensively. They are:
Clear cell sarcoma of the kidney (CCSK)
Malignant rhabdoid tumour of the kidney
Wilms Tumours are staged depending upon where the tumour has spread in the body and also what features they contain when looked at closely through a microscope.
The tumour is contained within one kidney and can be completely removed by surgery. The tissue layer surrounding the kidney (the renal capsule) is not broken and the cancer has not grown into blood vessels in or next to the kidney.
About 40% to 45% of all Wilms tumours are stage I.
The tumour has grown beyond the kidney, either into nearby fatty tissue or into blood vessels in or near the kidney, but can be completely removed by surgery without any apparent cancer left behind. Lymph nodes do not contain tumor.
About 20% of all Wilms tumours are stage II.
This stage refers to Wilms tumours that have spread to the lymph nodes or that may have ruptured or spread to localised tissues or structures. One or more of the following features may be present:
The cancer has spread to lymph nodes (bean-sized collections of immune cells) in the abdomen or pelvis but not to more distant lymph nodes, such as those inside the chest.
The cancer has invaded nearby vital structures so the surgeon could not completely remove it.
Deposits of tumor (tumor implants) are found along the lining of the abdominal space.
Cancer cells are found at the edge of the sample removed by surgery, indicating that some of the cancer still remains after surgery.
The cancer "spilled" into the abdominal space before or during surgery.
The tumor was removed in more than one piece – for example, the tumor was in the kidney and in the nearby adrenal gland, which was removed separately.
About 20% to 25% of all Wilms tumours are stage III.
The cancer has spread through the blood to organs away from the kidneys such as the lungs, liver, brain, or bone, or to lymph nodes far away from the kidneys. Tumours in other parts of the body are known as metastases.
About 10% of all Wilms tumours are stage IV.
Tumors are found in both kidneys at diagnosis. Also called bilateral Wilms tumours.
About 5% of all Wilms tumours are stage V.
Recurrent or relapsed Wilms tumours are not staged.
Based on the biopsy result, and after examining the whole tumour under the microscope, Wilms’ tumours can be divided into a number of groups based on knowledge about how these different types of tumours are likely to behave.
The tumour will be classified as 'low risk' 'intermediate risk' or 'high risk' depending on how likely, based upon what they have seen under the microscope, the tumour is likely to respond to treatment and if it is likely to relapse.
Certain factors result in a 'high risk' Wilms’ tumour. High risk tumours require more intensive (stronger) chemotherapy and closer observation following treatment:
Anaplastic Wilms’ tumour
About 5-10% of Wilms’ tumours have an appearance called anaplasia, which means the cells look very disorganised under a microscope. This is sometimes identified at biopsy, but may only be found when the whole tumour is examined after surgery.
Blastemal Wilms’ tumour
This group of high-risk tumours cannot be identified by looking at the biopsy because they occur when a particular type of early kidney cell survives the pre-surgery chemotherapy. These cells are known as blastemal cells. Tumours where most of these cells survive chemotherapy are called blastemal tumours.
Loss of Heterozygosity (LOH)
Information researchers have learnt about changes in genes of children with Wilms tumour have found that specific gene mutations or abnormalities can potentially play a role in tumour growth and tumour control and may also provide information about prognosis and risk of relapse.
Children whose tumours show loss of heterozygosity (a situation where one chromosome has a normal copy of a gene and one chromosome has a mutant or deleted copy, at chromosomes 16q and 1p, for example) appear to have worse survival rates and are more likely to relapse.