Molecular and diagnostic tests, explained.

Broad sequencing of many cancer-related genes, used when several possible findings are clinically relevant at once.

Limitations: a broad panel does not always produce a finding that changes management, tissue quality and quantity affect whether it can be performed, and turnaround time matters when a decision is urgent.

Testing for inherited variants that are present throughout the body rather than only in a tumour.

It is considered after family-history review and counselling, because results can have implications for relatives. Limitations: not all inherited risk is explained by the genes currently tested, and uncertain results are possible.

Protein-level staining performed on tumour tissue by the pathology laboratory.

It is often the first molecular information available. Limitations: results depend on the antibody and scoring system used, and protein expression does not always reflect the underlying genomic change.

Blood-based molecular testing that looks for tumour DNA circulating in the bloodstream.

It complements tissue testing rather than replacing it. Limitations: a negative result does not exclude an alteration, because not every cancer sheds detectable DNA into the blood.

A structured multidisciplinary discussion of molecular findings alongside the diagnosis, prior treatment and current clinical condition.

It is a review of information rather than a test, and its output is a documented discussion of options rather than a decision made in advance of consultation.

Sequencing technology used to examine many genes at once, in panels of varying size.

Panel size is chosen to match the clinical question. Limitations: regions outside the panel are not examined, and some structural changes are harder to detect than others.

Clinical review of an existing genomic or biomarker report, focused on what the findings mean in this particular clinical situation.

The review considers how the test was performed, how each finding is classified, and which findings could realistically be relevant to a treatment discussion.

Testing directed at one gene or a small group of genes when the clinical question is specific.

It can be faster and simpler than broad profiling, but by design it does not look beyond the genes selected.