Kidney cancer rarely affects children; about 45-50 paediatric cases are diagnosed in the UK each year. About 75 per cent of childhood kidney cancer occurs in the under-fives. The most common paediatric kidney cancer is Wilms’ tumour, which account for up to 95 per cent of childhood kidney cancers. Others include the following very rare types of kidney cancer:
- Renal cell carcinoma is the most common form of kidney cancer among adults, but it is rare in children younger than 15 years of age. However, it is more common in adolescents between 15 and 19 years of age. Renal cell carcinomas can spread to the lungs, bones, liver, and lymph nodes. Renal cell carcinoma in children is sometimes associated with genetic conditions, such as von Hippel-Lindau disease (an inherited condition that causes abnormal growth of blood vessels), tuberous sclerosis (an inherited disease marked by noncancerous fatty cysts in the kidney), neuroblastoma and sickle cell disease.
- Clear cell sarcoma of the kidney is a very rare type of kidney tumour that affects the supporting tissues in the kidney, and may spread to the lungs, bones, brain, and soft tissue. It is most common in infants and young children aged 1-4 years.
- Rhabdoid tumour of the kidney is a type of cancer that occurs mostly in infants and very young children. It grows and spreads quickly, often to the lungs and brain. A fault (mutation) in a gene called INI1 may increase the risk of developing rhabdoid tumours in the kidney.
- Ewing sarcoma (neuroepithelial tumour) of the kidney is rare and usually occurs in adolescents. These tumours grow and spread to other parts of the body quickly.
- Desmoplastic small round cell tumour of the kidney is a rare soft tissue sarcoma that most often affects boys, and which may develop and spread in the tummy (abdomen), pelvis or tissues around the testes. These tumours may also spread to the lungs and other parts of the body.
- Synovial sarcoma is most common in adolescents and grows and spreads quickly.
- Anaplastic sarcoma is most common in children younger than 15 years and often spreads to the lungs, liver, or bones.
- Cystic partially differentiated nephroblastoma is a very rare type of Wilms’ tumour made up of cysts.
- Mesoblastic nephroma is a non-cancerous (benign) tumour of the kidney that is usually diagnosed within the first year of life, and can usually be cured with surgery alone. One type of mesoblastic nephroma may appear on an ultrasound examination before birth or may occur within the first three months after the child is born.
- Multilocular cystic nephromas are non-cancerous (benign) tumours made up of cysts, which can occur in one or both kidneys. Children with this type of tumour could also have pleuropulmonary blastomas in the lungs.
These very rare kidney tumours are often treated in a similar way to unfavourable (high-risk) Wilms’ tumour, with surgery, chemotherapy and sometimes radiotherapy (see below). Mesoblastic and multilocular cystic nephromas, however, are benign tumours that can be cured using surgery alone and no other treatment.
Wilms’ tumour (sometimes called nephroblastoma) is a very rare type of kidney cancer, which mainly affects young children under five years of age. It is named after a German doctor, Dr Max Wilms (1867-1918), who first described it. About 40 children are diagnosed with Wilms’ tumour in the UK each year, and it is curable in around 90 per cent of cases. The vast majority of Wilms’ tumours affect only one kidney (unilateral), but in about 7 per cent of cases, both kidneys (bilateral) are affected.
A nephroblastoma is abnormal tissue, which grows on the outer part of one or both kidneys. It is thought that nephroblastomas originate from specialised cells in the developing embryo known as metanephric blastema, which are involved in the development of the child’s kidneys while they are still in the womb. These cells usually disappear at birth, but in some children they can still be found on the kidneys after birth, and are called nephrogenic rests. Children with this condition are at risk of developing a type of Wilms’ tumour.
Wilms’ tumour can be categorised depending on how the tumour cells appear under the microscope into two main types; favourable histology or unfavourable histology. Tumour cells with unfavourable histology look very large and not like normal kidney cells under the microscope. They are called anaplastic, and the cancer is less likely to be cured if anaplastic cells are widespread in the tumour. However, about 95 per cent of Wilms’ tumours have favourable histology and a high chance of a cure.
Causes and risk factors for Wilms’ tumour
The causes of Wilms’ tumour in most children are unknown. However, several risk factors have been identified. Anything that increases the risk of getting a disease is called a risk factor. However, having a risk factor does not mean that you or your child will necessarily get cancer.
In a few cases, it is thought that Wilms’ tumour may be part of a genetic syndrome that affects the growth and development of the child. A genetic syndrome is a set of symptoms or conditions that occur together, and is usually caused by abnormal genes. Certain birth defects can also increase a child’s risk of developing Wilms’ tumour. The following genetic syndromes have been linked to Wilms’ tumour:
- Wilms’ tumour, Aniridia, abnormal Genitourinary system and mental Retardation (WAGR syndrome) is a combination of abnormalities affecting the coloured part of the eye (the iris) where the iris is partially or totally absent (aniridia), the genitourinary tract (the kidneys, urinary tract, penis, scrotum, testicles, clitoris or ovaries), and possibly the brain, causing learning difficulties. Often children present with a milder form of WAGR with only some of these abnormalities.
- Beckwith-Wiedemann syndrome is a condition where children have larger than normal internal organs, often an enlarged tongue, and sometimes one arm or leg may be bigger than the other.
- Hemihypertrophy is a condition in which children have one side of the body slightly larger than the other. Hemihypertrophy is linked with Wilms’ tumour risk when it forms part of Beckwith-Wiedemann syndrome. However, most patients with isolated hemihypertrophy are not at increased risk of Wilms’ tumour development.
- Denys-Drash syndrome is a condition where boys do not develop normal male genitalia (penis, scrotum or testicles), and can be mistaken for girls. Their kidneys do not develop properly and eventually stop working. A Wilms’ tumour can grow in the damaged kidney.
There is also a slight risk due to a family history for Wilms’ tumour; between 1 and 2 out of every 100 children (1-2 per cent) with Wilms’ tumour have another family member with the disease, due to the inheritance of an abnormal gene from their parents.
Signs and symptoms of Wilms’ tumour
Wilms’ tumours can be very big when they are discovered due to the fact that the tumour is usually painless. In some cases the tumour can be much bigger than the kidney itself, although it is unusual for the tumour to have spread to other parts of the body from these large tumours.
The most common symptom is a painless swelling of the tummy. Other less common symptoms are listed below. Other conditions may cause the same symptoms, and a doctor should be consulted if you notice any of the following problems:
- Painless swelling or lump in the tummy (abdomen). This is the most common symptom of Wilms’ tumour. Occasionally, the tumour may bleed slightly, causing irritation and pain in the area surrounding the kidney.
- Blood is found in the urine in around 15-20 per cent of children with Wilms’ tumour.
- Raised blood pressure.
- High temperature or fever for no known reason.
- Loss of appetite.
- Weight loss.
- Upset stomach and/or vomiting.
- Shortness of breath and/or persistent cough is a symptom if the cancer has spread to the lungs.
Tests for childhood kidney cancer
The following tests and investigations may be used for the detection of childhood kidney cancer, including Wilms’ tumour:
- Physical examination of the body to check your child’s general health and to look for any lumps or swellings. A medical history of your child’s past illnesses and treatments will also be taken. This will most likely take place at your GP surgery and be repeated in hospital if your child is referred for further tests.
- Blood and urine samples will be taken to check your child’s kidney function and general health. They can take place in your GP surgery.
- Abdominal ultrasound scan and a CT scan are often done at the hospital to help diagnose the tumour and to assess its growth and spread. Occasionally scans of the chest and liver may be taken to check the spread of the disease. The information obtained from these scans is used to stage the progress of the disease (see below).
- Biopsy of the tumour is taken from most children to confirm the diagnosis made using the scans. There are two types of biopsy; during a needle biopsy cells are removed from the tumour using a needle inserted through the skin and into the tumour under local anaesthetic. During a tissue biopsy a piece of tumour is removed during a small operation under general anaesthetic. Sometimes, the surgeon will remove the entire tumour during this operation. The cell and tissue samples are sent to a pathologist, who examines them under a microscope to confirm the tumour as having favourable or unfavourable histology.
Staging of Wilms’ tumour
Wilms’ tumours can be categorised into stages, which describe the size and spread of the tumour. The information used to stage Wilms’ tumour is obtained from ultrasound and CT scans, and is used to help doctors decide on the most appropriate treatment. Often, the stage of your child’s tumour might not be known until after surgery, since most children have chemotherapy to shrink the tumour before surgery to remove it. A commonly-used staging system for Wilms’ tumours is as follows:
- Stage 1 The tumour affects only one kidney, is contained within the kidney, and has not begun to spread. It can be completely removed with surgery.
- Stage 2 The tumour has begun to spread beyond the kidney to nearby structures but it is still possible to remove it completely with surgery.
- Stage 3 The tumour has spread beyond the kidney, or the tumour has spread to the lymph nodes (glands), or it has not been completely removed by surgery.
- Stage 4 The tumour has spread to other parts of the body such as the lungs, liver, brain or bone to form metastases or secondary tumours.
- Stage 5 There are tumours in both kidneys (bilateral Wilms’ tumour).
- Recurrent cancer. The tumour has come back after initial treatment.
Treatment for Wilms’ tumour
Treatment for Wilms’ tumours will depend on the stage and spread of the disease, as described above, in addition to the histology of the tumour i.e. whether it is has favourable or unfavourable histology. Those children with a Wilms’ tumour of unfavourable histology or high-risk tumour will have stronger treatment.
- Surgery All children with Wilms’ tumour will have surgery. In most cases, a biopsy will be taken to confirm the diagnosis and to determine the histology of the tumour as favourable (standard or low risk) or unfavourable (high risk). The tumour will be removed by surgery, usually following a course of chemotherapy to shrink the tumour. Chemotherapy is not given to infants less than six months old. In most cases, the whole kidney is taken out (a nephrectomy), but occasionally only part of the kidney is removed (partial nephrectomy). In the case of bilateral Wilms’ tumour, surgeons try to ensure that as much healthy kidney remains as possible after removal of the cancerous tissue.
- Chemotherapy is usually given both before surgery to shrink the tumour and make it easier to remove (neo-adjuvant chemotherapy), and after surgery to kill off any cancer cells left behind after surgery (adjuvant chemotherapy), thereby reducing the risk of the tumour coming back or recurring. Chemotherapy is the use of drugs, which are toxic to cancer cells (cytotoxic drugs) but relatively harmless to normal cells. These drugs stop the cancer cells from growing and can be given alone or in combination with other cytotoxic drugs, depending on the stage and histology of the tumour. Chemotherapy is usually given by means of an injection into a vein, or via a drip, which requires the use of a catheter placed in a large vein, usually in the neck. The catheter is put in place during a small operation, and usually stays throughout the course of treatment.
- Radiotherapy may also be given, depending on the stage and histology of the tumour. Not all children need radiotherapy. Radiotherapy involves the use of high-energy radiation to destroy cancerous cells. It can be directed to the site of the affected kidney, thereby causing the least amount of harm to surrounding normal tissue. Sometimes, radiotherapy is used to treat the whole tummy area or the lungs, if the cancer has spread to the lungs. However, the use of radiotherapy depends on how well the cancer responds to initial chemotherapy, and it is not always needed.
Chemotherapy and radiotherapy are used to treat Wilms’ tumour that has spread to other organs and tissues (metastasised) i.e. stage 4 Wilms’ tumour.
Chemotherapy and radiotherapy often cause side-effects, which your doctor will discuss with you prior to treatment. These include feeling sick (nausea) and being sick (vomiting), diarrhoea, hair-loss, tiredness, bruising and bleeding, and an increased risk of infection. Additionally, some children may experience late side-effects many years later, including reduced bone growth, a change in heart and lung function, infertility, and a slightly-increased risk of developing cancer again in later life.
More information about Wilms’ tumours and childhood cancer in general can be found on the following websites:
Macmillan Cancer Support: Wilms’ tumour in children. http://www.macmillan.org.uk/Cancerinformation/Cancertypes/Childrenscancers/Typesofchildrenscancers/Wilmstumour.aspx
Cancer Research UK: Wilms’ tumour (kidney cancer in children). http://www.cancerresearchuk.org/about-cancer/cancers-in-general/cancer-questions/wilms-tumour
National Cancer Institute, at the US National Institutes of Health: Wilms tumor and other childhood kidney tumors treatment (PDQ®). http://www.cancer.gov/cancertopics/pdq/treatment/wilms/Patient#_295