Wilms tumour — the childhood kidney cancer, and why it is not adult kidney cancer

No. They are two different cancers that happen to grow in the same organ. Renal cell carcinoma, the kidney cancer of adults, begins in the mature cells lining the kidney tubules. Wilms tumour, also called nephroblastoma, begins in embryonal kidney tissue that should have matured into normal kidney before birth and instead persisted. Because the starting cell is different, almost everything downstream differs too: the age at which it appears, the way it is usually found, the staging system used, how sensitive it is to chemotherapy and radiation, and which team leads the care. If you are reading about adult kidney cancer to make sense of a child's diagnosis, most of it will not apply.

It is possible, but it is distinctly unusual. Wilms tumour is a disease of early childhood, and when the same diagnosis is made in a teenager or an adult, most centres will have the slides reviewed by an expert pathologist before accepting it. Adult cases are generally managed on paediatric protocols adapted for an adult body, which is why they belong with a team that treats both. In an adult found to have a kidney mass, renal cell carcinoma is by far the more likely answer, and that is where the assessment usually starts. A pathology second opinion is always reasonable when a diagnosis is this unexpected.

It means the pathologist examined the tumour cells and did not find anaplasia, the pattern of very large, irregular, abnormally dividing nuclei that marks out the harder-to-treat form of the disease. Most Wilms tumours are reported as favourable histology. The alternative, anaplastic or unfavourable histology, is recorded as focal or diffuse depending on how widely that pattern is spread through the tumour, because the difference changes how intensively treatment is given. Histology is read alongside the stage, never instead of it: a favourable histology tumour at a higher stage and an anaplastic tumour at a low stage are quite different situations, and the plan follows both lines together.

Because Wilms tumour is staged on a system of its own rather than on the adult TNM system, and it needs a category adult kidney cancer does not. Stages I to IV describe how far a tumour in one kidney has reached: confined and completely removed, extending a little beyond the kidney but still fully removed, left behind in the abdomen or in nearby lymph nodes, or spread to distant organs. Stage V means tumours are present in both kidneys at the time of diagnosis. It is grouped separately because the aim of treatment changes: preserving working kidney tissue on both sides becomes as important as clearing the tumour.

Most children with Wilms tumour have no family history and no inherited condition, and the tumour arises by chance. A minority are linked to a genetic predisposition, sometimes as part of a recognised syndrome with features such as absence of the iris, abnormalities of the urinary tract or genitals, kidney disease, or one side of the body growing larger than the other. Tumours in both kidneys, a very young child or another affected relative are the prompts to look harder. Where a predisposition is found, the child and sometimes siblings may be offered a schedule of ultrasound surveillance. Genetic counselling is delivered in-house at CION.

Because the two tumours respond very differently. Adult renal cell carcinoma is largely resistant to conventional chemotherapy, which is why adult treatment leans on surgery and, in advanced disease, on drug classes that work through the immune system or block the tumour blood supply. Wilms tumour is genuinely sensitive to chemotherapy, and to radiation, so combination chemotherapy is part of standard care for almost every child, given before surgery, after it, or both, depending on the protocol a centre follows. Surgery still matters, but it is one step in a sequence rather than the whole treatment. Chemotherapy and radiation planning are delivered in-house at CION; kidney surgery is coordinated with specialist partner surgeons.