What do I need to know about TNBC diagnosis and staging?

During the surgical evaluation, a biopsy will be performed. The biopsy should always be a "minimally invasive biopsy” as opposed to taking the patient to the operating room and removing it surgically. The common biopsy types include: 

1. Ultrasound guided core biopsies where the biopsy device is directed into the tumor by using an ultrasound machine.
2. Stereotactic vacuum assisted core biopsies where the biopsy device is directed into the tumor with the aid of a mammogram.
3. MRI guided vacuum assisted core biopsies where it is the MRI machine that directs the biopsy device. The idea is to remove a few cores of tumor for pathologic analysis regardless of which device is used. 

After the biopsy a small clip about the size of a pin head is placed in the center of the tumor. This will help identify the location of the tumor in the future. The small samples of tumor (taken during the biopsy) are sent to the pathology lab where the diagnosis of a triple-negative breast cancer is established. These biopsies are performed as an outpatient under local anesthesia and with little pain.

Healthy breast cells often have estrogen (ER) and progesterone (PR) receptors—proteins that bind to these hormones. Some breast cancers keep making these receptors; triple-negative breast cancer (TNBC) does not.

Why “triple-negative”?

• ER- and PR-negative: The cancer does not express estrogen or progesterone receptors, so hormone-blocking therapies don’t help.
• HER2-negative: The HER2 gene is present in everyone, but some cancers make too much HER2 (called overexpression) and can be treated with HER2-targeted drugs. TNBC has a normal HER2 result (not overexpressed).
• Together (ER-negative, PR-negative, and HER2-negative) define triple-negative.
   

Tumor grade (differentiation)
Grade describes how the cancer looks and behaves under the microscope:

• Well-differentiated (Grade 1): looks more like normal cells; tends to grow more slowly.
• Moderately differentiated (Grade 2).
• Poorly differentiated (Grade 3): looks very different; tends to grow/spread faster.
  Many TNBCs are Grade 3, which is one reason systemic therapy is commonly recommended.

Histologic or pathologic type of cancer 

You will frequently see terms like Invasive Ductal Carcinoma or Infiltrating Lobular Carcinoma. These are the two main types of breast cancers and can be of all grades and with or without receptors as described above.

What’s in your pathology report
Your report is the “spec sheet” for the biopsy or surgery specimen. It typically includes:

• Diagnosis/type (e.g., invasive ductal carcinoma)
• Tumor size (in mm/cm) and, after surgery, margin status
• Grade (1–3) and sometimes Ki-67 (cell-growth marker)
• Lymphovascular invasion (LVI)
• Lymph node findings (how many checked/positive)
• Receptor testing: ER, PR, HER2 results and the testing method (e.g., IHC; equivocal HER2 may be confirmed by ISH/FISH)
  These details are used to determine stage and tailor treatment.
   

What this means for treatment
Because TNBC lacks ER/PR/HER2, plans often rely on chemotherapy, surgery, and radiation, and—in specific situations—immunotherapy or other targeted options. If chemotherapy is given before surgery (neoadjuvant) and no invasive cancer is found in the breast and sampled nodes at surgery, that’s a pathologic complete response (pCR), which is associated with a better outlook (not a guarantee). 

Read more about common Treatment Options →

Helpful tip
Keep your report handy. Highlight ER/PR/HER2, grade, size, margins, and nodes, and bring questions to your next visit (see our Glossary and Treatment pages for plain-language explanations).

TNBC is most frequent in African American women, younger women and those with BRCA1 mutations. 

• Roughly 40% of breast cancers in African American women are triple negative compared to roughly 15% in Caucasian women. Additionally, most African American women who get triple negative breast cancer are pre-menopausal.  
• One other demographic group that is prone to have triple negative breast cancer are women who have BRCA1 mutations.

The association between BRCA1 mutations and triple negative breast cancers has led to research looking for a genetic predisposition to develop these types of cancers. 

• Studies have identified specific locations within genes that appear to be abnormal in a higher proportion of cases than in other types of breast cancer. 
• However, other than the BRCA1 gene, a specific gene causing this type of cancer has not been identified. 
• It is likely that a combination of genetic factors located in specific locations within the genome interactively play a role in the development of TNBC. Genetics is an active field of investigation in TNBC.

(Prognosis means the likely course of the disease or ultimately your expected recovery or recurrence projections)

Biology

• Triple-negative breast cancer (TNBC) lacks estrogen (ER), progesterone (PR), and HER2 receptors, so hormone-blocking medicines and most HER2-targeted drugs don’t work. TNBC can behave more aggressively early on, but the good news is that many TNBC tumors are very sensitive to chemotherapy. It’s common for tumors to shrink quickly—sometimes after just a few cycles.
• When chemotherapy is given before surgery (neoadjuvant) and no invasive cancer is found in the breast and sampled lymph nodes at surgery, that’s called a pathologic complete response (pCR). People who achieve pCR generally have a more favorable outlook. This strong response to chemotherapy is a key reason most TNBC treatment plans include chemo.

Prognosis

• You may read that TNBC has a worse prognosis than other breast cancer types. It’s important context: stage-for-stage, outcomes can be similar, and your individual outlook depends most on stage at diagnosis and response to therapy. About 30–40% of patients who receive neoadjuvant chemotherapy achieve pCR, which is linked with better outcomes. Newer options—such as immunotherapy in specific situations—are expanding choices and offer additional reason for optimism.
• Bottom line: earlier stage generally means better prognosis, and how your tumor responds to treatment matters. Try not to be discouraged by “gloom and doom” posts online; bring your questions to your care team so you can focus on the factors that apply to you.

• Are my ER/PR/HER2 results clearly negative? Was any confirmatory testing done?
• What is my grade and stage, and how does that guide treatment?
• If chemo is planned before surgery, what will define a good response for me?
• Do I need any additional tumor tests (e.g., PD-L1) to see if I’m eligible for immunotherapy?
• Can you walk me through my pathology report line by line?