Nephroblastoma, also known as Wilm’s tumour, is the most common renal tumour affecting children. It accounts for around 5% of childhood cancers. It usually occurs unilaterally, but can be bilateral.
Nephroblastoma affects around 80 children per year in the UK. It generally presents in the pre-school age group, with 3 and a half years being the median age at diagnosis. There is a slight female predominance (1).
As with all childhood cancers, the pathophysiology of nephroblastoma is poorly understood. Many tumours arise from “nephrogenic rests” – embryonal remnants seen in around 1% of infants at birth.
Genetics are also important; mutations of common tumour suppressor genes have been strongly implicated in nephroblastoma pathogenesis.
Risk Factors & Clinical Features
Children with certain genetic and overgrowth syndromes, such as WAGR (Wilm’s tumour, Aniridia, Genitourinary malformations, and Retardation), Denys-Drash and Beckwith-Wiedemann, are at an increased risk of nephroblastoma.
History may be only of an abdominal mass found incidentally or noted by parents during bathing or dressing in an otherwise well child. Children may also present with abdominal swelling, abdominal pain, fever or haematuria (2).
Examination is likely to reveal abdominal distension with unilateral or bilateral palpable renal masses. Hypertension may be noted. Rarely, in cases of advanced disease, signs of compression of other intraabdominal structures may be noted.
Other renal causes of an abdominal mass include polycystic kidney disease and hydronephrosis.
The most common malignant differential diagnosis of an abdominal mass in a pre-school child is neuroblastoma, which may also present with hypertension, abdominal pain or fever.
Neuroblastoma is associated with periorbital ecchymosis (dark circles under the eyes), an abdominal mass which crosses the midline, and signs of bone marrow infiltration.
Baseline blood tests, such as full blood count and urea & electrolytes, are usually performed to evaluate a child’s general health at presentation, although they are not diagnostic. A urine dip is usually performed to check for haematuria.
Imaging or Invasive tests
Initial characterisation of a renal/abdominal mass can be done using ultrasound, although CT or MRI is required for more detailed information and staging.
Biopsy is also required for definitive diagnosis. In Europe, biopsy is usually taken initially, whereas in the US, it is performed along with more definitive surgery.
Risk Scoring (if relevant)
|1||The tumour is only confined to the kidney and can be completely removed with surgery|
|2||The tumour has begun to spread beyond the kidney, but can still be completely removed with surgery|
|3||The tumour cannot be completely surgically resected because it has spread to neighbouring lymph nodes or ruptured before/during surgery|
|4||There are distant metastases, most commonly to the lungs.|
|5||There are bilateral tumours (each can be allocated an individual stage)|
Initial management consists simply of supportive care. Treat any co-existing infection and ensure nutrition and hydration are optimised.
Definitive and long‐term management
Stage 1 and 2 tumours may be treated solely with surgery. There is no additional benefit to giving chemotherapy which has additional risks later in life.
The aim of surgery is to preserve renal function while removing the malignant tissue.
Chemotherapy is used to reduce the volume of malignant tissue before surgery, or to treat any areas of malignant disease not removed by surgery.
Surgery usually consists of nephrectomy, although in bilateral disease there is usually an attempt to preserve as much functioning renal tissue as possible (to avoid the requirement for renal replacement therapy).
Complications and Prognosis
The prognosis for even metastatic disease is good, with over 85% of patients expected to be cured.
As many patients are left with a single functioning kidney, steps must be taken to protect the remaining kidney. These include general steps to maintain a healthy blood pressure, as well as avoidance of contact sports which could lead to abdominal trauma.
All patients who have had chemotherapy and/or radiotherapy should be followed up long term to monitor for potential late effects, such as cardiotoxicity.
|(1)||SZYCHOT, E., APPS, J. and PRITCHARD-JONES, K., 2014. Wilms’ tumor: biology, diagnosis and treatment. Transl Pediatr. 3(1), pp. 12–24.|
|(2)||IRTAN, S., EHRLICH, P.F. and PRITCHARD-JONES, K., 2016. Wilms tumor: “State-of-the-art” update, 2016. Seminars in pediatric surgery, 25(5), pp. 250-256.|
1st Author: Dr Amanda Friend
Senior reviewer: Dr Carmen Soto (Senior paediatric academic registrar)