Breast Cancer in Men

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Stages of Breast Cancer in Men

After a breast cancer diagnosis, one of the first steps is finding out whether the cancer has spread, and if so, how far. This is called staging.

Understanding the stage helps:

  • Determine how serious the cancer is
  • Guide treatment decisions
  • Estimate the likely outcome (prognosis)
  • Provide a common language for doctors and researchers studying cancer

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What is a cancer stage?

Cancer staging describes how much cancer is in the body and where it has spread. Stages range from 0 (very early) to IV (advanced). The lower the stage, the smaller the cancer and the less it has spread.

Although each person’s cancer is unique, breast cancers with similar stages tend to have a similar outlook and are often treated in much the same way.

What are the stages of breast cancer?

Doctors assign a stage from 0 to IV. In general, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more. For example:

  • Stage 0: Carcinoma in situ. The cancer is still only in the layer of cells where it started.
  • Stage I: Usually a smaller tumor, limited to the breast (or only small amounts of cancer in nearby lymph nodes).
  • Stage II: May be a larger tumor, and/or may have spread to a few nearby lymph nodes.
  • Stage III: May be an even larger tumor, or more lymph nodes are involved, or the cancer has grown into nearby areas. 
  • Stage IV: Cancer has spread to distant organs like the lungs, liver, bones, or brain.

However, factors like hormone receptor (HR) status, HER2 status, and the cancer’s grade can also affect the stage. This makes breast cancer staging more complex than it is for most other cancers. Ask your doctor about your specific stage and what it means.

How is the stage determined?

For both male and female breast cancer, doctors use the TNM system, developed by the American Joint Committee on Cancer (AJCC).

To determine the stage, doctors look at several key pieces of information:

  • Tumor (T): How large is the cancer? Has it grown into nearby areas?
  • Nodes (N): Has the cancer spread to nearby lymph nodes? If so, how many?
  • Metastasis (M): Has the cancer spread to distant organs such as the lungs, liver, bones, or brain?
  • Hormone receptor and HER2 status: Is the cancer ER, PR, and/or HER2 positive?
  • Grade (G): How much do the cancer cells look like normal cells?

In some cases, Oncotype DX Recurrence Score results may also be considered.

For more on the ER, PR, and HER2 status, the grade of the cancer, and the Oncotype DX test, see Breast Cancer in Men Early Detection, Diagnosis, and Staging.

Because breast cancer staging is so complex, it’s important to talk to your doctor about the stage of your cancer and what it might mean for you.

Clinical vs. pathological stage

There are two kinds of staging for breast cancer:

  • The clinical stage is based on physical exams, biopsies, and imaging tests. It is used to help plan treatment.
  • If surgery is done, the pathological stage (or surgical stage) can be determined. This is based on the clinical stage, plus what is found during surgery.

While the clinical stage is important, the pathological stage is often more accurate. For example, sometimes surgery might show the cancer has spread farther than was felt on exams or seen on imaging tests.

Understanding the TNM categories

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced.

T describes the main (primary) tumor's size and if it has spread to the skin or to the chest wall under the breast. Higher T numbers mean a larger tumor and/or wider spread to tissues near the breast.

  • TX: Primary tumor cannot be assessed.
  • T0: No evidence of primary tumor.
  • Tis: Ductal carcinoma in situ (DCIS), or Paget disease of the nipple with no associated tumor mass
  • T1 (includes T1mi, T1a, T1b, and T1c): Tumor is no more than 2 centimeters (cm) (3/4 of an inch) across.
  • T2: Tumor is more than 2 cm but not more than 5 cm (2 inches) across.
  • T3: Tumor is more than 5 cm across.
  • T4 (includes T4a, T4b, T4c, and T4d): Tumor of any size growing into the chest wall or the skin. This includes inflammatory breast cancer.

N indicates whether the cancer has spread to lymph nodes near the breast and, if so, how many lymph nodes are involved.

Can a few cancer cells affect staging?

The N category is based on how lymph nodes look under a microscope after they’re removed. As technology has improved, doctors can now find very small deposits of cancer cells. But it’s still not clear how much these tiny deposits affect a person’s outlook.

To affect staging, a deposit of cancer cells in a lymph node must be at least 200 cells or 0.2 millimeters (mm) across (less than 1/100 of an inch). Here’s how these findings are classified:

  • Isolated tumor cell clusters (ITCs): Smaller than 0.2 mm or fewer than 200 cells. These don’t change the stage but may be recorded with abbreviations like i+ or mol+ depending on the test used.
  • Micrometastases: Between 0.2 mm (or 200 cells) and 2 mm (about twice the width of a grain of rice). Micrometastases are counted only if there aren't any larger areas of cancer spread.
  • Macrometastases (or simply metastases): Larger than 2 mm. These are known to affect outlook and do change the N stage.

The small “p” before each N category below means that it is using definitions for pathological (surgical) staging.

  • pNX: Nearby lymph nodes cannot be assessed (for example, if they were removed previously).
  • pN0: Cancer has not spread to nearby lymph nodes, or it is only found as ITCs.
    • pN0(i+): Only ITCs were seen in routine stains or when a special type of staining technique, called immunohistochemistry, was used.
    • pN0(mol+): No cancer cells (even ITCs) are seen in the lymph nodes (even using special stains), but traces of cancer cells are detected using RT-PCR, a molecular test that can find very small numbers of cancer cells. (This test is not often used to find breast cancer cells in lymph nodes because the results do not influence treatment decisions.)
  • pN1: Cancer has spread to 1 to 3 axillary (underarm) lymph node(s), and/or tiny amounts of cancer are found in internal mammary lymph nodes (those near the breastbone) on sentinel lymph node biopsy.
    • pN1mi: Micrometastases (tiny areas of cancer spread) are seen in the lymph nodes under the arm. These areas of cancer are at least 0.2 mm across, but not larger than 2 mm.
    • pN1a: Cancer has spread to 1 to 3 lymph nodes under the arm with at least one area of cancer spread greater than 2 mm across.
    • pN1b: Cancer has spread to internal mammary lymph nodes on the same side as the cancer, but this spread could only be found on sentinel lymph node biopsy (it did not cause the lymph nodes to become enlarged).
    • pN1c: Both N1a and N1b apply.
  • pN2: Cancer has spread to 4 to 9 lymph nodes under the arm, or cancer has enlarged the internal mammary lymph nodes
    • pN2a: Cancer has spread to 4 to 9 lymph nodes under the arm, with at least one area of cancer spread larger than 2 mm.
    • pN2b: Cancer has spread to one or more internal mammary lymph nodes, causing them to become enlarged.
  • pN3: Any of the following:
    • pN3a: Either:
    • Cancer has spread to 10 or more axillary lymph nodes, with at least one area of cancer spread larger than 2 mm,
      OR
      Cancer has spread to the lymph nodes under the collarbone (infraclavicular nodes), with at least one area of cancer spread larger than 2 mm.
    • pN3b: Either:
      Cancer is found in at least one axillary lymph node (with at least one area of cancer spread greater than 2 mm) and has enlarged the internal mammary lymph nodes,
      OR
      Cancer has spread to 4 or more axillary lymph nodes (with at least one area of cancer spread greater than 2 mm), and tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy.
    • pN3c: Cancer has spread to the lymph nodes above the collarbone (supraclavicular nodes) with at least one area of cancer spread greater than 2 mm.

M indicates whether the cancer has spread (metastasized) to distant organs – for example, the lungs, liver, brain, or bones.

  • M0: No distant spread is found on exams or imaging tests.
  • cM0(i+): Small numbers of cancer cells are found in blood or bone marrow (found only by special tests), or tiny areas of cancer spread (no larger than 0.2 mm) are found in lymph nodes away from the underarm, collarbone, or internal mammary areas.
  • M1: Cancer has spread to distant organs (most often to the bones, lungs, brain, or liver).

side by side logos for American Cancer Society and American Society of Clinical Oncology

Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).

American Joint Committee on Cancer. Breast. In: AJCC Cancer Staging Manual. 8th ed. New York, NY: Springer; 2017:589-628. 

Last Revised: October 15, 2025

American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.

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