What is a Wilms tumour?

The term Wilms tumour is used to describe an embryonal carcinoma of the kidney which consists of blastocytic stromal and epithelial parts. Wilms' tumour, named after its discoverer, the Heidelberg surgeon Max Wilms, can also be called nephroblastoma and always describes a solid, malignant kidney tumour. Doctors assume that Wilms' tumour forms due to genetic disorders. In about 10 percent of all cases of the disease, congenital malformations can be held responsible for the Wilms tumour. As a rule, children under the age of 5 are more likely than average to develop Wilms' tumour. However, the disease can occur, albeit less frequently, in older children or in adults. Overall, Wilms' tumour accounts for just under 6 per cent of carcinomas in children.

How does a Wilms tumour develop?

A Wilms tumour forms from degenerated, primitive tissue. This is also the reason why the Wilms tumour resembles embryonic kidney tissue. Histologically, the Wilms tumour is composed of different types of tissue and contains immature precursor cells (blasters) of the kidney as well as other types of tissue, which are mature to different degrees. In addition to connective tissue, muscle, cartilage or epithelial tissue can also be found here, which is why Wilms tumours are also called mixed tumours.

Why does a Wilms' tumour develop?

The exact causes of a Wilms' tumour are still largely unknown. However, doctors know that changes in certain chromosomes and genes cause the tumour to develop. In particular, the so-called Wilms tumour gene? 1 (WT1 gene) on chromosome 11 is thought to play a key role in normal kidney development. Therefore, if an altered form is present, it can lead to tumour formation and other malformations. However, doctors assume that several genetic changes (mutations) must come together before a Wilms tumour forms.

How can a Wilms tumour be prevented?

Patients who are predisposed to Wilms' tumour or kidney malformation are advised to have quarterly clinical and imaging ultrasound examinations. Furthermore, in the case of a familial nephroblastoma, it is advisable to seek human genetic counselling and/or molecular genetic testing.

What are the symptoms of Wilms' tumour?

Wilms' tumour is most often manifested by a palpable abdominal tumour, which usually does not cause any pain or discomfort. Only in some cases can the following rather unspecific symptoms occur:

• Abdominal pain,
• Fever,
• Vomiting and nausea,
• Anorexia,
• increased occurrence of red blood cells (haematuria),
• High blood pressure (hypertension)

How is a Wilms tumour diagnosed?

A Wilms' tumour is diagnosed using standard imaging techniques such as an ultrasound scan or a computed tomography (CT) or magnetic resonance imaging (MRI) scan of the abdomen. An abdominal ultrasound can determine whether the Wilms tumour is a cyst or a solid tumour. Furthermore, it can be found out whether the vena cava or the renal veins are infiltrated. Computer or magnetic resonance imaging of the abdomen, on the other hand, can be used to determine the extent of the tumour. This is important to determine the spread of the tumour into the lymph nodes, the contralateral kidneys and the liver. Depending on the findings, a chest radiograph may also be ordered to determine whether there is pulmonary metastasis. The diagnosis of a Wilms' tumour is usually confirmed by the results of the image examination. A biopsy is usually not performed because the risk of contamination with peritoneal tumour cells is too great.

What stages of disease can a Wilms tumour be classified into?

In order to select a suitable treatment method, it is essential to classify the Wilms tumour into a disease stage. The following factors are taken into account:

• Has the tumour already exceeded the tumour capsule?
• Are blood vessels or neighbouring lymph nodes affected?
• Have distant metastases formed?
• Are both kidneys affected?

 
The International Society for Childhood and Adolescent Cancer (SIOP) also distinguishes between the following five stages of Wilms' tumour:

• Stage I: Localisation of the tumour to the kidney, without exceeding the tumour capsule; complete removal of the tumour is possible
• Stage II: The tumour capsule is exceeded; complete removal of the tumour is possible; the lymph nodes are not affected
• Stage III: Complete removal of the tumour is not possible; involvement of the regional lymph nodes or presence of a tumour rupture (tear in the tissue structure); no distant metastases present
• Stage IV: Presence of distant metastases, including in the lungs, liver, bones and/or brain
• Stage V: Presence of bilateral nephroblastoma

How is a Wilms tumour treated?

A Wilms tumour can theoretically be removed surgically or treated with chemotherapy or radiation. If the Wilms tumour occurs on one side, the doctor will first try to remove the tumour surgically, followed by chemotherapy to destroy any remaining tumour cells. If the tumour is particularly small, surgery may already be enough to cure the patient. The duration of adjuvant chemotherapy, on the other hand, always depends on the histology and the stage of the tumour.

What is the prognosis for a Wilms' tumour?

The chances of a Wilms tumour being cured depend on various factors. In addition to the tumour stage at the time of diagnosis, it also depends on the patient's general state of health. If a Wilms tumour develops in an adult, the prognosis is worse than in a child. This is because a Wilms' tumour in a child can usually be treated very well. The chances of cure for a Wilms' tumour that only involves the kidney are between 85 and 95 percent. However, even children in whom the Wilms tumour is more advanced have a 60 per cent (if the histology is poor) to a 90 per cent (if the histology is good) chance of cure. However, it can happen that the tumour develops again within 2 years after successful treatment.