Nephroblastoma (also known as Wilms' tumour) is a rare type of kidney cancer. This type of cancer mainly affects young children. It was first described by Dr Max Wilms – hence the name of this type of cancer.
It develops in cells known as nephroblasts, which are very specialized cells in the kidneys while the foetus is still in the womb. These cells usually disappear at birth, but in children who have developed nephroblastoma, they remain present and undergo malignant change.
This tumour is usually in one kidney, but rarely both kidneys may be involved. Nephroblastoma is quite different from the more common renal cancer (carcinoma) that occurs most frequently in adults.
Who gets it and who is at risk?
This is a cancer found almost exclusively in young children. It accounts for almost six percent of all childhood cancers, but is nevertheless fairly rare – only about eight in every million children under the age of 14 develop this disease.
It is usually diagnosed between the ages of two and three. Four out of every five children, who have this type of cancer, are diagnosed before the age of five. There is a higher incidence of this disease amongst black African and American children than white children. It occurs with almost equal frequency in boys and girls.
The exact cause of nephroblastoma is unknown, although it is suspected that genetic factors play a part in certain cases. About 1% of Wilms’ tumours are familial. It is thought that this condition results from mutations or changes in certain genes.
Several other rare conditions are associated with these particular genes. Approximately 15 percent of nephroblastoma cases are associated with certain birth defects. The commonest of these are hemihypertrophy, Aniridia, genitary urinary abnormalities and Beckwith Weidemann syndrome.
Associated syndromes or birth defects include:
WAGR (Wilms’ tumour, aniridia, genitourinary tract abnormalities and mental retardation) syndrome is a rare genetic condition. Children with these other conditions have a chance of one in three to develop nephroblastoma.
Hereditary Wilms’ tumour. In these cases there is a family history of the disease. It is characterized by bilateral tumours. It is a very rare condition – only one in twenty children diagnosed with Wilms’ tumour have bilateral tumours and only one in a hundred has a family history of the disease.
Aniridia. This refers to a condition where the iris of the eye does not develop fully. It is a congenital defect that can cause blindness. It is advisable that children with this condition be screened regularly for Wilms’ tumour.
Nephroblastomosis refers to the presence of small pockets of embryonal kidney tissue. The presence of these tissues seems to contribute to the likelihood of a tumour developing.
Denys-Drash syndrome. This syndrome is most often found in boys suffering from psuedo-hermaphroditism, a condition which makes it difficult to determine the sex of the child owing to genital abnormalities. The kidneys also do not function normally.
Hemihypertrophy is a condition found in children in which the one side of the body grows larger than the other. Children with this condition should be regularly screened for nephroblastoma, as the two conditions are regularly associated.
Beckwith-Weidemann syndrome. This is a congenital disorder characterised by hypoglycaemia at birth and internal organs that are larger than those of other children.
But the fact remains that 85 percent of children who develop this type of cancer do not have any of the above conditions.
Signs and symptoms
Unless a child's abdomen is palpated during a routine visit to a paediatrician and the condition diagnosed in this manner, the first sign of nephroblastoma is usually a large abdomen, or a protruding abdominal lump spotted by a parent. Blood in the urine is another presenting symptom. One in every four children who have this type of cancer will also have blood in the urine. Non specific symptoms sometimes found are abdominal pain, fever, weakness and shortness of breath, nausea and vomiting, and poor appetite. High blood pressure may also be present in children with nephroblastoma.
In a physical examination, a doctor can usually feel a lump in a child’s abdomen. Careful screening of the child’s medical history will follow.
Tests that can be done, include an abdominal CT scan and /or an ultrasound. Blood is taken to check kidney function and the urine is also analysed to check for signs of haematuria (blood in the urine).
Doctors also test whether the cancer has spread beyond the kidney most commonly to the lymphglands in the abdomen or to the lungs. It can also spread to the liver, bone, brain or distant lymph nodes. In most cases, however, the tumour does not spread outside the kidney.
Treatment depends on several factors, such as whether it is found in only one or both of the kidneys, the microscopic appearance of the tumour, the age of the child and the extent to which it may have spread to other parts of the body.
Treatment of this type of cancer has a very high success rate – between 85-90 percent of children diagnosed with this condition are fully cured, if they have access to the latest surgical techniques, drug therapies and radiation. Even older children and those with widespread disease can be cured.
Surgery is usually performed as soon as possible after the diagnosis. The surgical procedure, which is called a nephrectomy, entails the removal of the kidney containing the tumour in the case of unilateral tumour. The remaining kidney grows larger to compensate for the loss. During this operation, the other kidney is usually screened carefully to check whether it is tumour-free, which it is in over 90 percent of cases. If both kidneys are involved then the part of each kidney containing tumour will be removed (partial nephrectomies).
After surgery, all children undergo chemotherapy. If the tumour has spread to the abdominal lymph glands, radiotherapy will also be necessary.
As the causes are not yet fully understood, there is no known prevention. If there is a family history of this rare type of cancer, or a child suffers from any of the congenital conditions mentioned earlier on in the article, it is advisable that parents have their children screened.
When to see a doctor
If your child develops abdominal swelling, if you feel a lump or notice blood in the urine see your doctor as soon as possible. The earlier this condition is diagnosed, the greater the chances are of a full recovery.
Previously reviewed by Prof P.S. Hartley, Red Cross Childrens Hospital
Reviewed by Dr David Eedes, Oncologist, February 2011