Inherited cancer syndromes in children — an overview for anxious parents

Most cancers in children arise by chance — a combination of random genetic changes that accumulate over time in cells as they divide. A cancer predisposition syndrome, by contrast, is a condition in which a child is born with a genetic change — usually in one copy of a tumour-suppressor gene or a DNA-repair gene — that significantly increases the chance of one or more types of cancer developing during childhood or over a lifetime. The child's body cells already carry one of the changes needed for a tumour to form, so the threshold for cancer to develop is lower. Examples include Li-Fraumeni syndrome, hereditary retinoblastoma, familial Wilms tumour, and Lynch syndrome. Not every child who carries one of these genetic variants will develop cancer, but the risk is substantially higher than in the general population, which is why planned surveillance and early detection are central to care. Identifying a cancer predisposition syndrome changes how the child is followed long-term and has important implications for other family members.

Several features of a child's cancer diagnosis or family history may suggest an underlying cancer predisposition syndrome. These include: a cancer type that is rare at the child's age; cancer occurring in more than one organ or in both sides of a paired organ (such as both kidneys or both eyes); a family history of the same or related cancers in parents, grandparents, or siblings; more than one primary cancer developing at different times; or physical features outside the cancer that are associated with a known syndrome (such as distinctive birthmarks in certain conditions). When any of these features are present, the oncology team will typically recommend a genetics review. A clinical geneticist takes a detailed family history, reviews all available clinical information, and may recommend germline (blood-based) genetic testing to look for a specific gene change. It is also worth knowing that some children with a hereditary cancer syndrome have no family history at all — the gene change arose for the first time in that child.

The most commonly used test is a germline gene panel — a blood or saliva test that looks simultaneously at a large set of genes known to be associated with cancer predisposition. The panel tested will be guided by the type of cancer the child has, the clinical features, and the family history. In some cases a single-gene test is ordered first when a specific syndrome is strongly suspected (for example, testing TP53 in a child with a pattern consistent with Li-Fraumeni syndrome). The results of germline testing can confirm a syndrome, identify a variant of uncertain significance (meaning scientists do not yet know whether that particular change raises cancer risk), or come back negative — which does not always rule out a hereditary cause, as not all genes are yet known. Tumour testing (testing the cancer tissue itself rather than the blood) can provide additional clues about whether a germline cause is likely. The timing and scope of genetic testing is decided with the oncology and genetics team and will be explained to you step by step.

The implications for siblings depend on how the gene change is inherited and how it arose. Most hereditary cancer syndromes follow one of two inheritance patterns. In autosomal dominant syndromes (such as Li-Fraumeni syndrome or hereditary retinoblastoma), one changed copy of the gene is inherited from one parent, and each sibling has approximately a one-in-two chance of having inherited the same change. In autosomal recessive syndromes (such as Fanconi anaemia), a child needs two changed copies — one from each parent — to be affected; each sibling has a one-in-four chance of being affected. If the gene change arose for the first time in the affected child (de novo), siblings are at very low risk. Once the specific gene change in the family is identified, predictive genetic testing can be offered to siblings and parents. If a sibling is found to carry the same change, a surveillance programme can be set up before any symptoms appear — which is one of the most important benefits of identifying a hereditary cancer syndrome.

Genetic counselling is a process — typically one or more appointments with a clinical geneticist or certified genetic counsellor — in which your child's specific genetic findings are explained in plain language, the implications for family members are discussed, and the options for testing relatives are outlined. The counsellor will construct a detailed family tree, clarify the pattern of cancer in your family, explain what the specific gene variant means in practical terms, and discuss what surveillance or risk-reduction options exist. Genetic counselling is not just about delivering test results — it also addresses the emotional and psychological aspects of learning that a hereditary cancer risk runs in your family, and it helps parents think through what and how to share with extended family members. At CION, we coordinate genetic counselling referrals as part of a child's overall care plan, ensuring that no family has to navigate this alone.

Yes — when a child has a confirmed cancer predisposition syndrome, the follow-up and surveillance plan is tailored specifically to the cancers that syndrome is associated with. For example, a child with a syndrome that predisposes to kidney tumours will have regular abdominal ultrasounds at set intervals; a child with a syndrome associated with brain tumours will have periodic MRI scans of the brain and spine. The frequency and type of surveillance are based on published guidelines developed by international paediatric oncology groups, taking into account when cancers in that syndrome typically first appear and how quickly they can grow. The aim of surveillance is to detect any cancer at the earliest, most treatable stage. Your child's oncology team will provide a written surveillance schedule and explain what each examination or scan is looking for. Surveillance does not mean that cancer will develop — it simply means that if it does, it will be found and treated at the best possible point.