Genetic & molecular testing of a child's tumour — what it means for your family

Molecular testing — sometimes called genomic profiling, tumour gene testing, or molecular pathology — is a group of laboratory techniques that examine the genetic material inside a tumour’s cells. Where standard pathology under a microscope identifies what type of cancer is present, molecular testing answers a further question: why is this tumour growing the way it is, and what does that tell us about the best way to treat it? The results may reveal specific genetic changes (mutations), chromosomal rearrangements, or protein markers on the cell surface that guide the oncology team in choosing the most appropriate treatment approach. A molecular tumour profile report typically lists which genetic features are present, whether any of those features are clinically relevant, and sometimes whether an existing targeted treatment is a potential consideration. The report is always interpreted in the context of the child’s full clinical picture — it is one important piece of the puzzle, not the whole answer.

Two children can have tumours that look identical under a standard microscope but behave very differently — one growing slowly, one aggressively, one responding well to a particular treatment approach, one not. Molecular markers in the tumour’s DNA or proteins help explain these differences. For many childhood cancers — including certain types of leukemia, brain tumours, lymphomas, and solid tumours — knowing the molecular profile of the tumour is now considered part of the standard diagnostic work-up, not an optional extra. It guides decisions such as which treatment pathway to start, how intensive that treatment needs to be, and whether the child is a candidate for any risk-stratified or targeted approach. At CION, every child’s case is reviewed by a multidisciplinary tumour board that includes medical, surgical, and radiation oncologists — the molecular report is one of the documents on the table when they make their recommendation.

Most molecular tests on a solid tumour or lymph node biopsy sample take between one and three weeks to return results, depending on which specific tests are ordered and which laboratory is processing them. Some blood-cancer molecular tests (such as leukaemia cytogenetics) are prioritised and can be reported more quickly. It is important to know that molecular testing and initial treatment are not always sequential — in many cancers, treatment can be started based on the standard pathology diagnosis while molecular results are awaited. Your oncologist will explain their specific plan for your child: what tests have been ordered, approximately when results are expected, and how those results will influence the next steps. Please do not be afraid to ask directly: “Will starting treatment wait for molecular results, or will we start now?” Your team will give you a clear answer.

Molecular test results are interpreted by a specialist molecular pathologist or geneticist in the laboratory, who writes the report. That report then comes to your child’s oncology team, where it is reviewed alongside the standard pathology report, imaging findings, and the child’s clinical condition. At CION, cases with molecular testing are discussed at our tumour board — a scheduled meeting of oncologists from multiple specialties. The board considers the molecular findings as a group before any treatment change is made. This means no single doctor’s opinion determines how the molecular result is used — it is a team decision. The outcome of the tumour board is a written treatment recommendation, which your oncologist then discusses with you in full.

No — it means a specific targeted treatment is not available for that tumour’s molecular profile. Standard treatment pathways — which include chemotherapy, surgery, and radiation depending on the cancer type — do not require a molecular target to be effective. The majority of children with cancer are treated successfully with these established approaches. The purpose of molecular testing is to see whether the treatment plan can be refined or personalised on top of the standard pathway — not to replace it. If molecular testing reveals no actionable target, the standard treatment plan remains the appropriate choice. Your oncologist will explain what this means specifically for your child’s diagnosis and outlook.

This is a very practical and important question. The short answer is: in most cases, yes, the laboratory can perform both standard pathology (the microscope examination) and molecular tests from the same biopsy sample. Pathologists are experienced in allocating tissue from a single core needle biopsy or surgical specimen to multiple test types. However, for very small biopsies or for tumours in difficult locations where only a tiny sample could be taken, the amount of tissue can sometimes be a limiting factor. If your child’s oncologist plans to request molecular testing, this is factored into the decision about which type of biopsy to perform and how much tissue to collect. If you have been told that a repeat or additional biopsy may be needed to get enough material for molecular testing, this is a legitimate and not uncommon clinical situation — your team will explain the reasoning.