Breast Cancer Diagnosis: Tests, Procedures, and What to Expect
Written by North Editorial Staff | Clinically reviewed by Laura Morrissey, RN, BSN | Last reviewed: March 2026
Key Takeaways
Breast cancer diagnosis is a multi-step process: imaging identifies a suspicious area, and a biopsy confirms whether it is cancer. Imaging alone cannot diagnose breast cancer.
The most common first imaging test is a mammogram — abnormal findings lead to additional imaging (usually a diagnostic mammogram or ultrasound) and, if needed, biopsy.
A core needle biopsy is the standard method for diagnosing most breast cancers — it is minimally invasive, usually performed with imaging guidance, and provides enough tissue for both diagnosis and biomarker testing.
Biomarker testing — including hormone receptor status, HER2 status, and genomic profiling — is essential. It determines subtype and drives treatment decisions.
A new diagnosis can feel overwhelming, but you do not need to make immediate decisions. Taking time to understand your pathology report and consult with specialists — including potentially seeking a second opinion — is normal and appropriate.
How Breast Cancer Is Diagnosed
Breast cancer is diagnosed through a combination of imaging, physical examination, and tissue biopsy. No imaging test alone — not a mammogram, ultrasound, or MRI — can definitively diagnose or rule out cancer. Diagnosis requires a pathologist to examine actual tissue under a microscope.
The path to diagnosis typically begins in one of two ways: a screening mammogram detects something that was not felt, or a person notices a change — a lump, skin change, nipple discharge, or other symptom — and sees a doctor. From there, a defined sequence of tests follows.
Understanding each step helps reduce anxiety and prepares you to ask the right questions at each stage.
Mammography: The Starting Point
Screening vs. Diagnostic Mammogram
A screening mammogram is a routine X-ray of the breasts taken when there are no symptoms or known abnormalities. It is designed to detect cancer early, before it can be felt. When a screening mammogram shows something suspicious, you will be called back for a diagnostic mammogram, which is a more detailed X-ray that focuses on the area of concern, taken from multiple angles.
If you receive a call-back after a screening mammogram, it does not mean you have cancer. According to the American Cancer Society, approximately 10% of women who have screening mammograms are called back for additional imaging, and the majority of those call-backs turn out to be benign findings.
Understanding Mammogram Results: BI-RADS
Mammogram reports use a standardized scoring system called BI-RADS (Breast Imaging Reporting and Data System) to communicate findings. Scores range from 0 to 6:
BI-RADS 0: Incomplete — additional imaging needed
BI-RADS 1: Negative — normal
BI-RADS 2: Benign (definitely not cancer)
BI-RADS 3: Probably benign — short-interval follow-up recommended
BI-RADS 4: Suspicious — biopsy should be considered
BI-RADS 5: Highly suggestive of malignancy — biopsy strongly recommended
BI-RADS 6: Known malignancy — cancer has already been confirmed by prior biopsy
Most abnormal findings that require further workup fall into BI-RADS 3, 4, or 5. A BI-RADS 4 or 5 result leads directly to a recommendation for biopsy.
Ultrasound
Breast ultrasound uses sound waves rather than radiation to create images of the breast. It is not typically used alone as a screening tool in average-risk women, but it is highly valuable in several situations:
Characterizing a finding detected on mammogram — determining whether a mass is solid or fluid-filled (a simple cyst, which is benign, appears distinctly different from a solid mass on ultrasound)
Evaluating younger women with dense breast tissue, where mammography has limited sensitivity
Guiding biopsy needles to a target with precision
Evaluating a lump or change felt on physical exam
Ultrasound is painless, involves no radiation, and is widely available. It is often performed immediately following a diagnostic mammogram.
Breast MRI
Breast MRI (magnetic resonance imaging) uses a strong magnetic field and contrast dye to produce detailed images. It is more sensitive than mammography but also generates more false positives. Breast MRIs detect more benign findings that require additional workup.
MRI is typically used in specific situations rather than as a first-line diagnostic test:
Evaluating the extent of newly diagnosed breast cancer (how large, whether it involves additional areas)
Screening high-risk women (those with a lifetime risk ≥20%, known BRCA mutations, or prior chest radiation)
Assessing response to neoadjuvant chemotherapy (treatment given before surgery)
Evaluating implants or when other imaging is inconclusive
Biopsy: The Definitive Diagnosis
When imaging raises concern, a biopsy — removal of tissue for microscopic examination — is required to determine whether cancer is present. No treatment decision is made without pathological confirmation.
Core Needle Biopsy
Core needle biopsy is the standard diagnostic procedure for most suspicious breast findings. A hollow needle removes several thin cylinders (cores) of tissue from the area of concern. The procedure is:
Performed under local anesthesia where the skin is numbed; most patients feel pressure but not pain
Guided by ultrasound, mammogram (stereotactic biopsy), or MRI, depending on how the finding was identified
Minimally invasive — the incision is a few millimeters, typically requiring only a bandage
Usually completed in 30–45 minutes, including setup
Associated with mild soreness and bruising afterward, typically resolving within a few days
A small clip (a tiny metal marker) is usually placed at the biopsy site. This helps surgeons locate the area later if surgery is needed and confirms the right tissue was sampled on follow-up imaging.
Surgical Biopsy
Surgical biopsy removes a larger tissue sample, or the entire suspicious area, through a small incision. It is used when a core needle biopsy is not feasible (rare) or when a core biopsy produces uncertain results that require more tissue to interpret. Most breast cancers are no longer diagnosed by surgical biopsy; core needle biopsy has replaced it as the standard approach.
Fine Needle Aspiration (FNA)
Fine needle aspiration uses a thin needle to withdraw cells from a mass or lymph node. It can confirm cancer spread to lymph nodes but does not provide enough tissue for full biomarker testing and is not commonly used to diagnose primary breast cancer.
Pathology Report: Understanding Your Results
After biopsy, the tissue is analyzed by a pathologist, who prepares a report. This report is the foundation of your diagnosis. Key elements include:
Histologic type: What kind of cells the cancer originated from. Invasive ductal carcinoma (IDC) is the most common type (~80% of breast cancers); invasive lobular carcinoma (ILC) accounts for about 10–15%.
Grade: How abnormal the cancer cells look under the microscope. Grade 1 (well-differentiated) cells look relatively normal and tend to grow slowly. Grade 3 (poorly differentiated) cells look very abnormal and typically grow faster.
Hormone receptor status: Whether the tumor cells express estrogen receptors (ER) and/or progesterone receptors (PR). ER+ and/or PR+ tumors may respond to endocrine therapy.
HER2 status: Whether the tumor overexpresses the HER2 protein. HER2-positive tumors respond to targeted HER2-directed therapies.
Ki-67: A marker of how rapidly cells are dividing. Higher Ki-67 indicates faster-growing cancer.
Margins (if surgical biopsy): Whether the edges of the removed tissue are free of cancer cells.
The combination of histologic type, grade, hormone receptor status, and HER2 status determines the subtype of breast cancer — and subtype drives the treatment plan.
Biomarker and Genomic Testing
Beyond the standard pathology report, several additional tests may be ordered to further characterize the tumor and guide treatment.
Genomic Profiling (Gene Expression Tests)
For early-stage, hormone receptor-positive, HER2-negative breast cancer, genomic profiling tests assess the activity of a panel of genes in the tumor to estimate the risk of recurrence and predict the benefit of chemotherapy. The most widely used tests include:
Oncotype DX (Recurrence Score): Assesses 21 genes; a score of 0–100 predicts 10-year recurrence risk and whether chemotherapy will add benefit. Most widely validated in postmenopausal women with node-negative disease; also validated for premenopausal women (TAILORx and RxPONDER trials).
MammaPrint: A 70-gene assay that classifies tumors as low or high genomic risk; validated in the MINDACT trial.
These tests inform one of the most consequential treatment decisions: whether a patient with early-stage HR+ breast cancer needs chemotherapy in addition to endocrine therapy, or whether endocrine therapy alone is sufficient.
BRCA and Hereditary Testing
If you are diagnosed with breast cancer and have features suggestive of hereditary risk (early age at diagnosis, triple-negative subtype, strong family history, Ashkenazi Jewish heritage), germline genetic testing for BRCA1, BRCA2, and other genes may be recommended. Results affect your own surgical decision-making (e.g., bilateral vs. unilateral mastectomy) and have implications for blood relatives.
Staging: Understanding How Far the Cancer Has Spread
Once cancer is confirmed, staging determines the extent of disease. This typically involves:
Physical examination of lymph nodes
Sentinel lymph node biopsy: Removal and analysis of the first lymph node(s) to which breast cancer would spread — performed at or before primary surgery
Imaging (CT scan, PET scan, or bone scan) for higher-stage disease or when distant spread is suspected
Full staging is captured using the TNM system: T (tumor size), N (lymph node involvement), M (metastasis). Staging guides treatment recommendations and prognosis.
What to Do After a Diagnosis
A breast cancer diagnosis does not require immediate action within hours or days. Taking time to understand your diagnosis fully before consenting to surgery or other treatments is both appropriate and advisable.
Steps worth considering:
Request copies of all reports: Your pathology report, imaging reports, and biopsy results are yours. Having them in hand lets you discuss your case with other providers.
Seek a second opinion: Getting another pathologist or oncologist to review your case is standard practice, not a slight to your current doctors. It can confirm the diagnosis or reveal additional information.
Ask about a multidisciplinary tumor board: Many breast cancer programs present new cases to a panel of surgeons, medical oncologists, radiation oncologists, and pathologists, who collectively recommend a treatment plan.
Ask about clinical trial eligibility: Many trials enroll patients at diagnosis, before or in place of standard treatment. Asking your oncologist about trial options early, and using a trial finder to search independently, ensures you don’t miss an opportunity.
Understanding your diagnosis completely — your subtype, stage, biomarker status, and treatment options — puts you in the best possible position to make decisions. Explore breast cancer treatment options or search for breast cancer clinical trials to learn what’s available for your specific situation.
Frequently Asked Questions
Can a mammogram diagnose breast cancer?
No. A mammogram can identify a suspicious finding, but diagnosis requires a biopsy — the removal of tissue that a pathologist examines under a microscope. A mammogram showing a suspicious mass leads to additional imaging and, if concern persists, biopsy. Many mammogram abnormalities turn out to be benign.
What is a core needle biopsy and does it hurt?
A core needle biopsy removes small cylinders of tissue from the suspicious area using a hollow needle. The area is numbed with local anesthesia first — most patients feel pressure but not significant pain during the procedure. There is usually mild soreness and bruising afterward for a few days. It is minimally invasive and takes about 30–45 minutes.
How long does it take to get biopsy results?
Most biopsy results are available within 3–7 business days. Some pathology reports — particularly those requiring additional staining for hormone receptors, HER2 status, or other markers — may take up to 7–10 days. Ask your doctor or nurse when to expect results and how you will receive them.
What does it mean if my tumor is ER-positive?
ER-positive means the tumor cells have estrogen receptors — they use estrogen to fuel their growth. This is actually favorable: ER-positive tumors tend to grow more slowly and respond well to endocrine therapies such as tamoxifen or aromatase inhibitors, which block estrogen’s effect on cancer cells. ER-positive is the most common breast cancer subtype.
Should I get a second opinion on my breast cancer diagnosis?
Yes — seeking a second opinion is standard practice and is strongly encouraged, especially for complex cases or before major treatment decisions. Many major cancer centers offer second-opinion reviews of pathology and imaging. A second opinion can confirm your diagnosis, provide additional nuance on subtype or staging, and sometimes identify clinical trials you were not previously offered.
References
American Cancer Society. (2024). Breast Cancer Early Detection and Diagnosis. https://www.cancer.org/cancer/types/breast-cancer/screening-tests-and-early-detection.html
American College of Radiology. (2013). ACR BI-RADS Atlas, 5th Edition. https://www.acr.org/Clinical-Resources/Reporting-and-Data-Systems/Bi-Rads
National Cancer Institute. (2024). Breast Cancer Diagnosis. https://www.cancer.gov/types/breast/patient/breast-treatment-pdq#section/all
Gradishar, W. J., et al. (2024). NCCN Clinical Practice Guidelines in Oncology: Breast Cancer. National Comprehensive Cancer Network. https://www.nccn.org/guidelines/guidelines-detail?category=1&id=1419
Sparano, J. A., et al. (2018). Adjuvant Chemotherapy Guided by a 21-Gene Expression Assay in Breast Cancer (TAILORx). New England Journal of Medicine. https://www.nejm.org/doi/10.1056/NEJMoa1804710
Cardoso, F., et al. (2016). 70-Gene Signature as an Aid to Treatment Decisions in Early-Stage Breast Cancer (MINDACT). New England Journal of Medicine. https://www.nejm.org/doi/10.1056/NEJMoa1602253