What is a Wilms tumour?
Wilms tumour is a type of kidney cancer that affects young children. The tumour is an abnormal proliferation of a type of cell called a metanephric blastema cell. These cells are embryological remnants leftover from kidney development in the womb. Tumours grow within the kidney itself, a tumour confined to the kidney may be termed ‘intrarenal’ in the medical evidence. 40% of tumours extend from the kidney into the renal vein and a smaller number extend into the ureter and sometimes the bladder.
It is the fifth most common cancer in childhood. The mean age at diagnosis of children affected is 3.5 years. In 6% both kidneys are affected by Wilms tumour.
10% of children who develop Wilms tumour have a recognisable congenital abnormality, the most common are listed below. Such children are routinely screened for Wilms tumour through early childhood:
- WAGR syndrome (Wilms Aniridia Genitourinary anomalies mental Retardation) – 50% of children with WAGR develop Wilms tumour and 5% of children with Wilms tumour have this syndrome – aniridia means the iris or coloured part of the eye is absent.
- Denys-Drash Syndrome – rare, Wilms tumour develops in most cases. Other features are abnormal genitals (e.g. Intersex) mesangial renal sclerosis – abnormal kidney changes that cause nephrotic syndrome and renal failure.
- Horseshoe kidney – single abnormally shaped kidney.
- Hypospadias – abnormally placed urethral opening.
- Cryptorchism – testis not present in scrotum.
- Beckwith Weidemann Syndrome – 7.5% develop Wilms tumour. Other features include abdominal hernia of varying severity, macroglossia (large tongue), enlarged internal organs and hemihypertrophy (overgrowth of one half of the body leading to asymmetry).
5 year survival after treatment of Wilms tumour has improved dramatically in the UK from 29% in the 1960s to 80% in the most recent figures.
Incidence/prevalence
Around 70 children develop Wilms tumour in the UK each year. The vast majority will be under 5 years old at diagnosis. Overall survival is very good - at least 80%. The majority of children have good prognosis disease and expected survival approaches 100% in this group.
