How is Breast Cancer Staged?
With the information found in the pathology report, your physician will assign your breast cancer a stage, ranging from 0 to IV. Staging your cancer helps your breast cancer team determine which treatment options will be most effective for your cancer. Your cancer’s stage is based on several characteristics of the cancer, including:
- Whether your cancer is invasive or noninvasive
- Whether your cancer tests positive or negative for:
- Estrogen or progesterone receptors
- HER2 protein or gene number
- Lymph node status, referring to whether or not cancer was found in any of your lymph nodes
- Cancer grade, characterized by a score of 1 to 3 that reflects how different the cancer cells look from normal cells. A score of 1 is low grade meaning the cells look most like normal cells and 3 is high grade with cells that appear very different from normal cells. Grade 2 is in between. In general, Grade 1 and 2 cancers are less aggressive, while Grade 3 cancers have a slightly higher chance of spreading.
- Oncotype Score
In general, breast cancers are staged using these guidelines:
What is Stage 0 (carcinoma in situ) Breast Cancer?
The term in situ means the cancer cells are found only in their initial location. For example, ductal carcinoma in situ means abnormal cells are found only in the ducts, and have not spread beyond them. Lobular carcinoma in situ means the abnormal cells are confined to the lobules. In Paget disease of the nipple, cancer cells are found only in the nipple. Noninvasive cancers are considered stage 0.
What is Stage 1 Breast Cancer?
Stage I describes invasive breast cancers, meaning that cancer cells are spreading beyond the ducts or lobules and invading surrounding breast tissue.
Stage IA means that the tumor measures 2 centimeters (cm) or smaller, and cancer cells have not spread beyond the breast.
Stage IB means the tumor is 2 cm or smaller, or possibly there’s no breast tumor but small clusters of cancer cells are found in lymph nodes. But, if the tumor is estrogen-receptor-positive or progesterone-receptor-positive, it may be classified as stage IA.
What is Stage 2 Breast Cancer?
Stage II cancers are invasive cancers that may be larger and/or involve nearby lymph nodes in the underarm (axillary nodes) or near the breastbone.
Stage IIA: refers to either of these situations:
- The breast tumor is 2 cm or smaller, or possibly there’s no breast tumor, but clusters of cancer cells (2 mm or larger) are found in 1 to 3 underarm lymph nodes or in the nodes near the breastbone;
- The breast tumor is between 2 cm and 5 cm in size, with no lymph node involvement. But, if the cancer is HER2-negative, it may be classified as stage I; or stage IA if it’s also estrogen-receptor-positive, progesterone-receptor-negative and has an Oncotype DX score of 9.
Stage IIB: refers to one of these situations:
- The breast tumor is between 2 cm and 5 cm in size, and small clusters of cancer cells (smaller than 2 mm) are found in lymph nodes
- The breast tumor is between 2 cm and 5 cm in size, and cancer has spread to 1 to 3 underarm lymph nodes or the nodes along the breastbone. But, if the cancer is also HER2-positive, estrogen-receptor-positive and progesterone-receptor-positive, it could be classified as stage I.
- The breast tumor is larger than 5 cm, with no lymph node involvement.
What is Stage 3 Breast Cancer?
Stage III cancers are invasive cancers that are considered locally advanced disease and are divided into these subcategories:
Stage IIIA refers to one of these situations:
- The breast tumor is 5 cm or smaller and has spread to 4 to 9 underarm lymph nodes that are attached to each other or nearby tissue, or to the lymph nodes behind the breastbone;
- The breast tumor is larger than 5 cm and small clusters of cancer cells (less than 2 mm) are found in lymph nodes.
- The breast tumor is larger than 5 cm and has spread to 1 to 3 underarm nodes or to the nodes near the breastbone.
Note: Even if the tumor is larger than 5 cm and cancer is found in 4 to 9 lymph nodes, it may be down staged to stage IB if it is also estrogen-receptor-positive, progesterone-receptor-positive, HER2-positive, and still grade 2.
Stage IIIB refers to a breast tumor of any size that has grown into the chest wall or skin of breast causing swelling or an ulcer and the cancer may have spread to:
- Up to 9 underarm lymph nodes; or
- to the lymph nodes behind the breastbone
Note: Even if the tumor is larger than 5 cm and cancer, is found in 4 to 9 lymph nodes, and grade 3, it may be down staged to stage IIA if it’s also estrogen-receptor-positive, progesterone-receptor-positive, HER2-positive.
- Inflammatory breast cancer is typically considered at least stage IIIB
Stage IIIC refers to a tumor of any size that has spread to the chest wall, and/or the skin of the breast and has spread to:
- Up to 10 or more underarm lymph nodes
- Lymph nodes above or below the collarbone
- Underarm lymph nodes and nodes near the breastbone
Note: Stage IIIC cancers of any size may be down staged to stage IIIA if the tumor is grade 2 and estrogen-receptor-positive ad progesterone-receptor-positive. However, cancer that has spread to the skin may be inflammatory breast cancer.
What is Stage 4 Breast Cancer?
Stage IV cancers are considered advanced or metastatic disease. Stage IV refers to cancer that has spread beyond the breast and nearby lymph nodes to other areas of the body such as the lungs, liver, bones, brain or to distant lymph nodes. Stage IV tumors can be any size.