Geisinger: What Are the Stages of Breast Cancer?

When a person is diagnosed with breast cancer, they may wonder whether the cancer has spread and, if so, how far. A doctor can answer these questions after determining the stage of the disease.

Staging refers to the process of describing how extensive the cancer is, including the size of the tumor and whether it has spread to surrounding tissues or other parts of the body.

Generally, a lower stage number indicates that the cancer has spread less. Stage 0 breast cancer is the earliest, non-invasive form of the disease, while stage 4 is the most advanced and means the cancer has spread beyond the breast to other areas of the body.

Staging also helps doctors determine the most effective treatment approach and predict how successful that treatment may be. It allows them to create a more personalized treatment plan, as each stage presents different therapy options. A lower stage typically indicates a more localized cancer, which can often be treated less aggressively and may have a more favorable outcome. In contrast, higher stages of breast cancer often involve more extensive disease that requires more intensive treatment strategies.

How Stages of Breast Cancer Are Determined

Based on the results of a physical examination, biopsy, and/or imaging tests, a doctor assigns a stage to the breast cancer diagnosis. The clinical staging system is guided by the TNM classification, which evaluates three key factors:

• (T): The size of the tumor
• (N): The presence of cancer in the lymph nodes
• (M): Whether the cancer has metastasized, or spread, to distant parts of the body

In addition to the TNM classification, doctors may also consider other biological markers, such as the presence of estrogen, progesterone, or HER2 receptors, and how rapidly the tumor cells are likely to grow and spread.

Together, these factors help define the cancer’s stage, providing a more detailed diagnosis and enabling a more targeted and personalized treatment plan.

Stages of Breast Cancer Explained

Breast cancer is classified into five main stages — from stage 0 to stage 4 — each with distinct characteristics and corresponding treatment options.

Stage 0 Breast Cancer

Stage 0 breast cancer, also known as ductal carcinoma in situ (DCIS), represents the earliest and non-invasive form of the disease. In this stage, abnormal cells are present within the lining of the breast milk ducts but have not spread into surrounding tissues.
Typically, there are no noticeable symptoms, and the prognosis is excellent. Treatment often includes surgical removal of the affected tissue, commonly followed by radiation therapy to prevent recurrence.

Stage 1 Breast Cancer

Stage 1 breast cancer indicates early invasive disease, in which the tumor measures up to 2 centimeters (cm) and has not spread beyond the breast. In some cases, cancer cells may be found in a very small number of nearby lymph nodes.
Possible symptoms include a breast lump, nipple discharge, or changes in breast shape. The prognosis is highly favorable, and treatment generally involves a combination of surgery, radiation therapy, and, depending on the tumor’s biological characteristics, hormone therapy or chemotherapy.

Stage 2 Breast Cancer

Stage 2 breast cancer is defined by a larger tumor (between 2 and 5 cm) and/or cancer that has spread to nearby lymph nodes but remains confined to the breast region.
Common symptoms may include a noticeable lump, swelling, or discomfort in the breast. The prognosis remains very positive, with treatment typically consisting of surgery, radiation therapy, and systemic treatments such as chemotherapy and hormone therapy, depending on the cancer subtype.

Stage 3 Breast Cancer

Stage 3 breast cancer is considered locally advanced. The tumor is often larger than 5 cm and/or has spread to multiple nearby lymph nodes and possibly surrounding tissues, such as the breastbone or chest wall.
Symptoms may become more pronounced and include lumps in the armpit, skin or nipple changes, and breast pain. While the prognosis is still favorable with appropriate care, treatment is usually more aggressive, often combining surgery, radiation therapy, chemotherapy, and targeted therapies.

Stage 4 Breast Cancer

Stage 4 breast cancer is the most advanced stage, indicating that the disease has metastasized beyond the breast to distant organs such as the bones, liver, lungs, or brain.
Symptoms can vary depending on where the cancer has spread and may include chest pain, persistent cough, bone pain, or fatigue. At this stage, the focus shifts toward controlling the disease and improving quality of life through palliative care and systemic treatments, including chemotherapy, targeted therapy, and hormonal therapy.

Importance of Breast Screenings and Early Detection

Early detection remains the most effective defense against breast cancer. Along with routine clinical breast examinations, annual mammograms are the most reliable method for monitoring breast health and identifying cancer in its earliest stages.

The recommended age to begin yearly mammograms is 40. However, individuals with a family history of breast cancer or other risk factors should consult their doctor to determine whether earlier screening is appropriate.

In addition to screenings, reducing controllable risk factors can help lower the likelihood of developing breast cancer. These lifestyle choices include:

• Eating a healthy, balanced diet
• Exercising regularly
• Limiting alcohol consumption
• Avoiding smoking
• Maintaining a healthy weight

Anyone who notices changes in their breasts or develops new symptoms should contact their doctor immediately — even if a recent mammogram showed no abnormalities. Detecting breast cancer early allows for more effective treatment and may enable the use of less invasive therapies.

For the latest health and wellness tips and advice, visit geisinger.org/balance.

Rebecca Jordan, DO, is a general surgeon specializing in breast surgery.