Twenty years ago, testing for an inherited cancer risk usually meant looking at one or two genes, one at a time. Today a single sample can be read across dozens of genes in one run. This explainer walks through what multi-gene panel sequencing actually does, how the results are graded, why some answers come back “uncertain,” and what all of this means for cancer screening decisions. It draws on guidance from the American College of Medical Genetics and Genomics (ACMG), the National Comprehensive Cancer Network (NCCN), and peer-reviewed studies.
From single genes to panels
The shift was driven by next-generation sequencing (NGS), which reads millions of DNA fragments in parallel rather than one stretch at a time. Instead of ordering a stand-alone BRCA1 or BRCA2 test, a clinician can request a panel that simultaneously examines genes such as PALB2, CHEK2, ATM, the Lynch-syndrome mismatch-repair genes, and others associated with hereditary cancer risk. The ACMG’s secondary-findings list (version 3.3, 2025) now spans 84 genes, of which roughly 28 relate to hereditary cancer.
The practical payoff is breadth. In one multicentre study, multi-gene panel testing identified pathogenic variants that single-gene testing would have missed, and other cohorts have reclassified previously “non-informative” patients into a defined syndrome after a broader panel. The trade-off is that the more genes you read, the more ambiguous results you also turn up.
How a variant gets a verdict
Finding a DNA change is only the first step; the harder question is what it means. Since 2015, most laboratories follow the ACMG/AMP framework, which sorts each variant into one of five tiers using 28 weighted criteria spanning population frequency, computational prediction, functional studies, and family segregation data.
| Classification | Plain-language meaning |
|---|---|
| Pathogenic (P) | Strong evidence the variant causes disease |
| Likely pathogenic (LP) | Probably disease-causing; usually acted on clinically |
| Variant of uncertain significance (VUS) | Not enough evidence to call either way |
| Likely benign (LB) | Probably harmless |
| Benign (B) | Strong evidence the variant is harmless |
A token such as rs80357906 simply names a specific variant; the classification tells you how much weight to put on it.
The VUS problem
The uncertain category is the panel era’s central challenge. Variants of uncertain significance make up nearly 40% of hereditary-cancer variants reported in the public ClinVar database, and the rate of uncertain findings rises as more genes are added to a panel. A VUS is not a positive result and generally should not, on its own, drive surgery or other major decisions.
The encouraging news is that uncertainty is often temporary. As laboratories accumulate population data, functional assays, RNA-sequencing splicing studies, and family information, many variants are eventually re-graded. In one large analysis, about 7.7% of uncertain variants were reclassified, and the great majority of those (over 90%) were downgraded toward benign rather than upgraded. This is why genetics services may recontact patients years later with an updated interpretation.
What this means for screening
Classification matters because it changes risk numbers, and risk numbers change screening. Carriers of a pathogenic BRCA1 variant face a mean cumulative breast-cancer risk around 57% and an ovarian-cancer risk near 40%; for BRCA2 the figures are roughly 49% and 18%. A pathogenic PALB2 variant confers a lifetime breast-cancer risk of about 53%. NCCN guidelines translate findings like these into specific recommendations — earlier and more frequent imaging, consideration of risk-reducing options, and cascade testing for relatives.
- A pathogenic or likely pathogenic result typically prompts enhanced, gene-specific screening.
- A VUS usually means screening is guided by personal and family history, not the variant itself.
- A negative result does not erase risk that comes from a strong family history.
Kit and assay details matter too: a token like OG-500 refers to a collection device, not a result, and sequencing depth and gene coverage affect how confidently a laboratory can call certain regions.
The PROMPT heritage
Interpreting these panels at scale was the motivation behind data-sharing efforts such as PROMPT (Prospective Registry of Multiplex Testing), a hereditary-cancer registry cited in ASCO’s Journal of Clinical Oncology that pooled carrier data precisely to resolve the flood of uncertain variants that panel testing produced. That collaborative model — many laboratories and patients contributing evidence — remains the engine behind today’s reclassifications, even where individual registries are no longer enrolling.
The bottom line
Multi-gene panel sequencing lets a single test survey many cancer-risk genes at once, catching variants that older single-gene testing missed. The cost is more uncertain results, but standardised ACMG/AMP grading and growing shared databases steadily turn uncertainty into clearer answers. A result is only as useful as its interpretation — and interpretation is exactly what is improving fastest.
Educational explainer, not medical advice. For your own testing or results, speak with a clinician or genetic counsellor.