Molecular Profiling of Breast Cancer and DCIS
Laboratory tests describe how a tumour behaves and which treatments may help. Not every molecular test is useful for every person.
The key things to know
- Biomarkers help select treatment.
- Tumour profiling does not equal inherited testing.
- Order a test when its answer can change care.
The routine biomarkers
Invasive breast cancers are usually tested for estrogen receptors, progesterone receptors, and HER2. Hormone receptors can indicate benefit from endocrine therapy, while HER2 helps guide HER2-targeted treatments. These results are read alongside tumour size, grade, and lymph-node findings. A label such as triple-negative describes missing receptors, not a complete description of an individual's outlook.
Gene-expression tests
Some tests measure the activity of several genes in a tumour to estimate recurrence risk and, in selected early hormone-receptor-positive cancers, help judge whether chemotherapy may add benefit. They are not required for every cancer. The decision depends on tumour features, menopausal status, nodal involvement, and whether the result would actually change treatment. Ask what clinical question a proposed test answers.
How DCIS differs
DCIS remains within the milk ducts. Its size, grade, margins, and estrogen-receptor status can inform care. HER2 testing is not routinely used in DCIS in the same way as in invasive cancer. Commercial risk tests for DCIS have limitations and should not replace discussion of established clinical and pathology findings or be interpreted as a promise that recurrence will or will not happen.
Tumour tests versus inherited tests
A tumour profile is different from inherited genetic testing. Most molecular findings in a tumour do not automatically mean relatives carry the same change. Sometimes a result prompts a separate genetics referral. If cancer recurs, a new biopsy may be useful because receptor status can change. Keep a copy of the full report and ask your team to explain uncertain or borderline results.
Take these questions to your appointment
- Which test results affect my treatment?
- Would this additional test change the recommendation?
Sources & review
This is original educational content based on the sources below, not reproduced textbook material. Website supervisor: Dr. Nizar Ismail. Individual medical review of this article is pending.
- NCI: Tests for Breast Cancer Biomarkers ↗
- NCI: How Is Breast Cancer Diagnosed? ↗
- NCI: Ductal Carcinoma in Situ ↗
This information cannot replace diagnosis or a personal treatment plan. Consult your care team about symptoms or decisions about your treatment.