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PubMed This is a summary of 25 peer-reviewed journal articles Updated
Pathology · Invasive Breast Carcinoma of No Special Type

Biology, Subtypes, and Your Pathology Report

At a Glance

For invasive ductal carcinoma, the pathology report shows how the tumor looks and behaves through its grade, hormone receptors, HER2, and Ki-67, plus margins and lymph nodes after surgery. These results help your oncology team discuss treatment options.

Your pathology report is the “blueprint” of your cancer. It contains the data your oncology team uses to understand the biology of your Invasive Ductal Carcinoma (IDC)—now professionally known as Invasive Breast Carcinoma of No Special Type (IBC-NST)—and to build your personalized treatment plan [1][2].

The Nottingham Grading System: Assessing Aggressiveness

While “stage” tells you how far the cancer has spread, the grade tells you how the cells are behaving. Pathologists use the Nottingham Grading System to score three specific features of the cancer cells under a microscope [3][4]:

  1. Tubule Formation: This measures how much the cancer cells still look like the normal tube-like structures of the breast. A lower score means more tubes are present [3].
  2. Nuclear Pleomorphism: This looks at the size and shape of the nucleus (the “brain” of the cell). Higher scores mean the nuclei look more abnormal and vary significantly in size [3].
  3. Mitotic Count: This is a count of how many cells are actively dividing (mitosis). A higher count means the cancer is growing more quickly [3][5].

The scores from these three categories are added together to determine your overall grade:

  • Grade 1 (Score 3-5): Low grade; slow-growing [6].
  • Grade 2 (Score 6-7): Intermediate grade [7].
  • Grade 3 (Score 8-9): High grade; more aggressive and faster-growing [6][5].

Biomarker Categories: The “Fingerprint” of Your Cancer

Your team uses biomarkers—proteins on the surface or inside the cancer cells—to categorize your cancer. These are immunohistochemical (IHC) surrogate categories that help estimate the cancer’s intrinsic gene-expression subtype, which helps in choosing your medication [8][9]. However, treatment also depends on stage, nodal status, grade, menopausal status, and your own goals.

  • Hormone Receptor-Positive (HR+): The cancer cells have receptors for Estrogen (ER) and/or Progesterone (PR). These cancers use hormones to grow. If your report shows ER or PR at 1% or higher, it is considered positive [10][11]. (Note: “Low positive” ER of 1–10% is molecularly heterogeneous and may behave differently.)
  • HER2-Positive: The cancer has too much of the HER2 protein, which sends strong growth signals to the cells. This is defined as an Immunohistochemistry (IHC) score of 3+ or an equivocal IHC score of 2+ combined with a positive FISH/ISH gene test [12][13].
  • Triple-Negative Breast Cancer (TNBC): The cancer tests negative for ER, PR, and HER2. Because it doesn’t have these “ears” to listen for hormone or HER2 signals, it relies on surgery, radiation, and chemotherapy. For selected high-risk early-stage disease, immunotherapy is used with chemotherapy before and after surgery [2][14].

Evolving Treatment Descriptors: HER2-Low and HER2-Ultralow

In the past, HER2 was seen as a simple “yes” or “no.” However, new treatments like antibody-drug conjugates (ADCs) have changed this, introducing evolving descriptors that are especially relevant in advanced or metastatic settings [15][16].

  • HER2-Low: Your IHC score is 1+ or 2+ (with a negative FISH test). While traditionally “HER2-negative,” you may be eligible for specific targeted therapies depending on the drug and prior treatment [17][18].
  • HER2-Ultralow: This is a very new terminology for tumors with just a tiny, faint amount of HER2 (IHC 0 with slight staining) [19][20].
  • HER2-Null/Undetected: No HER2 protein is detected (IHC 0 with no membrane staining) [19][21].

The Role of Ki-67

You may see a percentage for Ki-67. This is a “proliferation marker” that shows what percentage of cells are currently dividing [22][23]. While a higher Ki-67 can suggest a more aggressive cancer, there is no universal cutoff. It is not used alone to make treatment decisions because the testing methods can vary between labs [24][5][25].

Pathology Completeness Checklist

Ensure your report includes these core “must-have” items [1][10]:

  • [ ] Histologic Type: Usually “Invasive Breast Carcinoma of No Special Type” (or IDC).
  • [ ] Tumor Size: The exact measurement of the invasive area.
  • [ ] Nottingham Grade: Both the total grade (1, 2, or 3) and the individual scores for tubules, nuclei, and mitosis.
  • [ ] ER and PR Status: Reported as a percentage (e.g., “ER 95% positive”).
  • [ ] HER2 Status: The precise IHC score (0, 1+, 2+, or 3+) and FISH/ISH result if IHC was 2+.
  • [ ] Lymphovascular Invasion: Whether cancer cells were seen in the small blood or lymph vessels.
  • [ ] Margins & Lymph Nodes: (If you have already had surgery) How close the cancer was to the edge of the removed tissue and whether it was found in the lymph nodes [7].

Common questions in this guide

Is invasive ductal carcinoma the same as invasive breast carcinoma of no special type?
Invasive ductal carcinoma (IDC) is the older and more familiar name for invasive breast carcinoma of no special type (IBC-NST). A pathology report may use either term, and both generally refer to the same diagnosis.
What does my Nottingham grade say about my breast cancer?
Nottingham grade describes how abnormal the cells look and how quickly they appear to be dividing; it is different from stage, which describes how far the cancer has spread. The score combines how much the cells form normal-looking tubes, how unusual their nuclei look, and how many cells are dividing. Grades 1, 2, and 3 correspond to scores of 3–5, 6–7, and 8–9, with higher grades generally indicating faster-growing, more aggressive behavior.
How do ER, PR, and HER2 results affect my breast cancer subtype?
ER and PR show whether cancer cells have estrogen or progesterone receptors; 1% or more is considered hormone-receptor positive. HER2 is positive when the IHC score is 3+ or when an IHC score of 2+ is confirmed by a positive FISH or ISH test. Along with stage, lymph-node status, grade, menopausal status, and personal goals, these results help classify the cancer and guide treatment.
What is the difference between HER2-low, HER2-ultralow, and HER2-negative?
HER2-low usually means an IHC score of 1+ or 2+ with a negative FISH test. HER2-ultralow describes an IHC score of 0 with a tiny amount of faint staining, while HER2-null or undetected means no HER2 protein is detected. These labels may affect eligibility for certain targeted medicines, especially in advanced or metastatic disease, and the impact depends on the specific drug and prior treatment.
What does Ki-67 mean on a breast cancer pathology report?
Ki-67 is a percentage estimating how many cancer cells are dividing. A higher result can suggest faster growth, but there is no universal cutoff and testing methods can vary between laboratories. Doctors do not use Ki-67 alone to decide treatment.
What should be listed in a complete invasive ductal carcinoma pathology report?
An important report usually lists the histologic type, invasive tumor size, Nottingham grade and its component scores, ER and PR percentages, and the HER2 IHC result, with FISH or ISH testing when needed. After surgery, it may also include lymphovascular invasion, margins, and lymph-node findings. Ask your care team to explain any missing or unclear item.
What does low-positive ER mean for hormone therapy?
An ER result of 1–10% is called low positive, so it meets the definition of hormone-receptor positive. Tumors in this range can have mixed biological features and may behave differently from tumors with higher ER expression, so the expected benefit of hormone therapy needs an individualized discussion. Stage, grade, PR, HER2, lymph nodes, and your overall treatment plan also matter.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What was my exact Nottingham grade, and what were the scores for each of the three categories (tubules, nuclei, and mitosis)?
  2. 2.Based on my ER, PR, and HER2 results, what is my breast cancer 'molecular subtype'?
  3. 3.Does my HER2 result fall into the 'low' or 'ultralow' category, and does that change my treatment options now or in the future?
  4. 4.What was my Ki-67 percentage, and how much weight are you giving that number in my treatment plan?
  5. 5.Is my ER status 'low positive' (1–10%), and if so, how does that affect the expected benefit of hormone therapy?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

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This page is for informational purposes only and does not constitute medical advice. Your pathologist and oncology team should interpret your specific pathology report and discuss treatment options with you.

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