Biomarkers and genomic terms, explained plainly.

A structural change involving the ALK gene, found in a small proportion of lung cancers and some other cancers.

Where an ALK rearrangement is reported, it may be relevant to how treatment options are discussed. It is usually identified on tissue or blood-based molecular testing, and its relevance depends on the cancer type and the wider clinical picture.

Related:Molecular testingReport interpretation

A change in the BRAF gene seen in melanoma, thyroid, colorectal and other cancers.

Clinical relevance depends on the specific variant and the cancer type: the same variant can be interpreted quite differently in different cancers, and can be considered only in the appropriate clinical context.

Genes involved in repairing damaged DNA. Changes may be inherited (germline) or present only in the tumour.

The distinction between an inherited change and one confined to the tumour matters for both treatment discussion and assessment of family risk. Germline findings are discussed with genetic counselling rather than reported in isolation.

Related:Germline testing contextTargeted therapy

Changes in the EGFR gene, most often discussed in lung cancer.

Different EGFR variants behave differently. Some are well characterised and may help inform a treatment discussion; others have little established significance and are interpreted in clinical context.

Related:Molecular testing

A receptor assessed in breast, gastric and some other cancers, either as protein expression or as amplification of the ERBB2 gene.

Reporting now includes lower expression levels as well as clearly positive results, and the scoring system used depends on the assay and the cancer type.

Related:Molecular testing

Receptor expression measured on tumour tissue, most often in breast cancer.

Receptor status may be relevant to whether hormone-directed approaches are considered, alongside the stage, prior treatment and the individual clinical situation.

A marker of impaired DNA mismatch repair, reported on tissue testing.

It can be relevant to treatment discussion and sometimes prompts assessment for an inherited condition such as Lynch syndrome. That assessment is a clinical process, not a conclusion drawn from the marker alone.

Related:Cancer genetics

A protein measured on tumour or immune cells within a tissue sample.

Different scoring systems are used depending on the cancer and the assay, so two reports are not always directly comparable. A given score may be relevant to an immunotherapy discussion but does not by itself predict response.

A count of the mutations detected across the regions of DNA that were sequenced.

Interpretation depends on the assay used, the cancer type and the clinical picture. Thresholds differ between laboratories and are considered alongside other findings rather than in isolation.

A genomic change whose clinical meaning is not established.

A VUS is not evidence of benefit or harm, and classification can change over time as more data accumulate. It is not treated as an actionable finding.