To determine how advanced a case of breast cancer is, healthcare providers use the American Joint Committee on Cancer breast cancer classification system. They use the stages of breast cancer to compare cancer cases and survival rates and to make treatment decisions. 

Breast cancer classification considers the tumor’s size, if the cancer is in the lymph nodes, and if it has spread to other organs. The breast cancer classification system also considers the tumor’s grade, genetic makeup, and other characteristics like hormone receptor status.

Cancer stages are typically labeled 1 to 4 (sometimes referred to by the Roman numerals I, II, III, and IV). Some precancerous growths are staged as stage 0 breast cancer. The higher the stage, the more advanced the cancer is. Treatment options will typically be more aggressive for more advanced cancers, and the prognosis, or outlook, is worse.

This article will cover the breast cancer stages and how treatable and curable they are. It will cover the symptoms associated with each stage and grade of breast cancer and the survival rate for each.

Stages vs. Grades of Breast Cancer

The stages of breast cancer refer to how advanced the cancer is. Healthcare providers use information like the tumor’s size and how far it has spread to determine breast cancer’s stage. Your doctor uses your cancer’s stage to: 

• Gauge how advanced your cancer is
• Determine your chances of survival
• Plan your cancer treatment options
• Find clinical trials for you to participate in

Generally, stage 0 breast cancer is defined as abnormal cells in the breast that have not started to spread to other tissues. Breast cancer stages 1, 2, and 3 tumors are cancers that may have started to spread to the lymph nodes and grow larger.

Stage 4 cancers are the most advanced and deadly cancers; they have metastasized and spread to distant body parts. 

A crucial part of determining a cancer’s stage is assessing its grade. Breast cancer grading is done on a piece of tissue taken from the tumor during a breast biopsy. A doctor called a pathologist studies the sample of tissue removed during the biopsy under the microscope to give it a grade.

The grade represents how wild the cells look and how many of them are actively dividing. Breast cancer grades range from 1 to 3. 

At lower grades, cells look more normal and are slower growing, but in higher grades, the cells are growing faster and look very different from normal cells. Higher-grade cancers are more aggressive.

Aside from the grade, other factors that influence the stage of breast cancer include genetic changes to the cancer, genetic risk factors for breast cancer, the cancer’s hormone receptor status, and the type of cancer it is.

Different cancer types are often graded slightly differently due to their aggressiveness. For example, triple-negative breast cancer does not have estrogen and progesterone hormone receptors and expresses low levels of the protein human epidermal growth factor receptor 2 (HER2).

Stage 0

Stage 0 breast cancer is also called ductal carcinoma in situ (DCIS) or Paget's disease of the breast. It is a precancerous, or noninvasive, abnormal growth in the breast.

These cells may look abnormal, but the growth isn't cancerous (yet). It hasn't invaded any other parts of the breast or surrounding tissues or organs.

Stage 0 breast cancer generally has no signs or symptoms. Often there isn't a lump that you or your healthcare provider can feel. One potential symptom is slight discharge from the nipple. Most of the time, symptoms aren't what lead to a stage 0 breast cancer diagnosis, but instead it is found with a mammogram and breast biopsy.

Stage 0 cancers may be treated with surgery to remove the mass and hormone therapy to ensure the cancer doesn't develop further. Some people argue that DCIS shouldn't be classified as cancer but instead as a cancer risk factor.

Some research suggests that only around 20% of DCIS cases eventually become invasive cancer or come back after surgery. The cancer after surgery may not even be the same as the DCIS.

Knowing this, some experts suggest that some DCIS cases may not require treatment; instead, active surveillance may be an option. Active surveillance includes regular physical exams and mammograms to see if the growth progresses into invasive cancer.

Cases of DCIS make up about 20% to 25% of all breast cancers.

Stage 1

Stage 1 (or stage I) breast cancer typically has started to grow into surrounding breast tissues. Breast cancers that are stage 1 either have not spread into the lymph nodes (stage 1A) or only spread minimally into the lymph nodes (stage 1B).

The most common symptom of early breast cancer is a new lump or mass. Most breast lumps are due to benign breast conditions and are not cancer. But a painless, hard mass with irregular edges is more likely to be cancer. Breast cancer lumps can be soft, round, tender, or painful.

Stage 1 breast cancers are usually treated with surgery to remove the mass, potentially with radiation therapy to treat the area. Hormone therapies and chemotherapy can help reduce the risk of cancer returning. Lymph nodes will also be biopsied or dissected to look for signs of cancer. Targeted therapies may also be used for HER2-positive stage 1 cancer.

The National Cancer Institute’s SEER (Surveillance, Epidemiology, and End Results) database collects information on cancers in the United States. They break cancers down into the following three stage variables:

• Localized: The cancer hasn’t spread.
• Regional: Cancer has infiltrated nearby tissues or lymph nodes.
• Distant: Cancer has metastasized to other body parts.

According to the SEER database, 63% of breast cancer cases are diagnosed at the localized stage, including stage 1 and some stage 2 cancers.

Stage 2

Stage 2 (or stage II) breast cancers are typically larger or have spread to more lymph nodes.

Stage 2 breast cancers may cause symptoms like:

• Breast or nipple pain
• Dry or flaking nipple or breast skin
• Nipple discharge (other than breast milk)

If the cancer has spread to the lymph nodes, you may feel a lump under the arm or near the collarbone.

Treatment options for stage 2 breast cancers include surgery to remove the tumor (a lumpectomy and radiation to the breast or the chest wall) or breast removal (mastectomy), which may or may not require radiation treatments.

Chemotherapy may be used to shrink the tumor before surgery and is commonly recommended to reduce the risk of recurrence. Lymph nodes will be removed and biopsied, and others may need to be treated with radiation. 

You may also get hormone therapy, targeted therapy, or immunotherapy, depending on the characteristics of your cancer. Immunotherapies may be an option for high-risk (stages 2 and 3) triple-negative cancers.

Stage 3

Stage 3 (or stage III) breast cancer is often called invasive breast cancer. It has spread farther than stage 2, involves more lymph nodes, or increased, but has not metastasized beyond the local tissues and organs near the breast.

Symptoms of invasive breast cancers are similar to earlier-stage cancers. They can include:

• Breast skin that is red, dimpled, or puckered 
• An unexplained rash on the breast
• Fluid coming out of the nipple (that is not breast milk)
• A lump near the breast or armpit
• A change in the shape or feel of the breast

Stage 3 breast cancers also include inflammatory breast cancers. Inflammatory breast cancers are more aggressive but rare—only about 1% to 5% of breast cancers are inflammatory. But they often do not present the same way as other breast cancers and can be missed. They usually do not cause a breast lump and might not appear on a mammogram. Symptoms also develop quickly, within three to six months.

Symptoms of inflammatory breast cancers include:

• Swollen breast skin
• Redness over one-third or more of the breast
• “Orange peel” like pitting or thickening of the skin
• A retracted or inverted nipple
• One breast becomes larger due to swelling
• One warm and heavy breast 
• Tender, painful, or itchy breast

Treatment for stage 3 breast cancers typically involves a combination of surgery (lumpectomy or mastectomy) and chemotherapy to shrink the tumor before and radiation after surgery to treat the chest wall or lymph nodes. Lymph nodes will also likely be removed during surgery. 

Targeted therapies, including hormone therapy, can also be used depending on your cancer’s specific characteristics. According to the SEER database, 28% of breast cancers are found once they’ve become regional. These cancers include some stage 2 and most stage 3 breast cancers.

Stage 4

Stage 4 (or stage IV) breast cancer is the deadliest and is not considered curable. It is also called metastatic breast cancer or advanced breast cancer. It has, by definition, spread to organs in other parts of the body. These organs may include the lungs, skin, bones, liver, or brain.

Common symptoms of advanced cancers include:

• Pain
• Fatigue and weakness
• Loss of appetite
• Weight changes
• Nausea and vomiting
• Constipation
• Shortness of breath
• Bone pain that becomes constant, fractures.
• Headaches, nausea, facial numbness, and changes in speech, vision, or balance due to cancer in the brain.
• Pain in the right side of the abdomen, weakness, poor appetite, and yellowing of the eyes and skin from cancer in the liver.
• Lung pain, shortness of breath, and persistent cough.

Treatment options for stage 4 breast cancer aim to ease symptoms, improve quality of life, and extend life span. This may include hormone therapy, targeted therapy, chemotherapy, immunotherapy, radiation, or surgery.

According to the SEER database, about 6% of breast cancers are stage 4 before being detected.

Factors Influencing Success of Early Stage Treatment 

The stage of your breast cancer is essential in deciding your treatment options. In early-stage breast cancer, essential factors influencing effective treatment include:

• The presence of hormone receptors like estrogen and progesterone on the tumor cells
• The presence of large amounts of HER2 protein on the tumor cells
• Specific genetic changes, like BRCA mutations 
• Your overall health and personal preferences
• Whether you have gone through menopause
• How fast the cancer is growing

Factors Influencing Success of Late Stage Treatment 

Some additional factors influence the success of the treatment of late-stage breast cancers. These include:

• Your overall health 
• Personal preferences on continuing treatment and palliative care (care aimed at providing comfort rather than cure)
• Where the cancer is located
• If the cancer is in major organs
• If cancer comes back after treatment
• The side effects of aggressive treatment
• Targeted treatments or immunotherapy options
• What previous treatments you’ve tried
• If the cancer’s hormone receptor or HER2 status changes

Summary

Healthcare providers stage breast cancer using the American Joint Committee on Cancer breast cancer classification system. This helps them decide what treatment to give and how the cancer might affect the patient. The system looks at:

• Tumor size 
• Cancer's presence in nearby lymph nodes
• If cancer has spread to other parts of the body
• The cancer cells' grade
• Presence of hormone receptors
• Genetic factors
• Other traits of the tumor, including HER2 status

There are four main stages of breast cancer. The higher the stage, the more advanced the cancer is and the harder it is to treat.

Stage 0 is abnormal cells in the breast, ductal carcinoma in situ (DCIS). It doesn't typically present with symptoms. It's often detected through a mammogram and biopsy. Stage 0 breast cancer treatment may include surgery and hormone therapy. Some may not require treatment. It has a high survival rate.

Stage 1 breast cancer has started to grow into the breast tissue. Stage 2 breast cancer is bigger or may have spread to nearby lymph nodes. Stage 2 breast cancer symptoms may include breast pain, skin changes, or nipple discharge. Treatment options for these stages include surgery, chemotherapy, radiation, and targeted therapies.

Stage 3 breast cancer has spread even farther and may have started to affect the skin or chest wall. These are invasive and inflammatory breast cancers. Symptoms include skin changes, rashes, and breast pain. Treatment includes surgery, chemotherapy, radiation, and targeted therapies.

Stage 4 is breast cancer has spread to other body parts. It is also called metastatic breast cancer. It is the most advanced and is considered incurable. Symptoms of advanced breast cancer include pain, fatigue, and organ-specific issues. Treatment aims to manage symptoms and improve quality of life. It may involve hormone therapy, chemotherapy, immunotherapy, and radiation.

Five-year survival rates for breast cancer are 99% for localized (stage 1 and some stage 2), 86% for regional (stage 3 and some stage 2), and 31% for distant (stage 4).