This page was reviewed under our medical and editorial policy by
Daniel Liu, MD, Plastic and Reconstructive Surgeon
This page was updated on September 20, 2022.
Breast cancer is an abnormal growth, or tumor, that forms in tissue in the breast and that may spread to other tissues and organs. An important part of diagnosing breast cancer involves identifying its stage, which ranges from stage 0 to stage 4 based on the size of the breast tumor and how far, if at all, it spreads beyond its point of origin.
Some stages also have sub-stages, such as 1A and 1B. The care team will determine the stage of cancer based on many factors, including imaging tests, the size of the tumor and the analysis of tissue samples taken during surgery or a breast biopsy. Then, they use this information to recommend a treatment regimen. Stage 0 and stage 1 are early-stage cancers, whereas stage 4 is considered the most advanced because it’s spread to other areas in the body.
Stage 0 breast cancers are often called pre-cancers, pre-invasive cancers or breast carcinoma in situ. With stage 0, abnormal cells in the breast have some cancer characteristics, but they have not yet spread into other tissues or organs.
Of the two forms of stage 0 breast cancer, the most common is called ductal carcinoma in situ (DCIS) or intraductal carcinoma. About 20 percent of all breast cancers are stage 0 DCIS, according to the American Cancer Society (ACS). With DCIS, the abnormal cells are limited to tissues that line the duct of the breast.
A rare disease called Paget’s disease of the breast is also classified as stage 0 breast cancer. It’s characterized by abnormal cells that develop in the skin of the nipple and areola. Up to 90 percent of the time, it’s found along with DCIS or an advanced-stage breast cancer in the same breast, according to the ACS. When it accompanies DCIS or advanced-stage breast cancer, then that form of Paget’s disease is no longer considered Stage 0, but is instead staged according to the associated tumor.
Very early-stage DCIS breast cancers typically don’t have symptoms. Though it’s sometimes possible to feel a small, hard lump, most people discover they have stage 0 breast cancer through regular mammogram screenings.
Paget’s disease of the breast is likely to cause noticeable changes, such as:
Because it’s not possible to predict whether a stage 0 breast cancer will invade the breast tissue around it, most people undergo treatment, which may include surgery, radiation therapy and hormone therapies such as tamoxifen.
Surgical options for stage 0 breast cancer include breast-conserving surgery (also called a lumpectomy) to remove the area of the breast with abnormal cells, or a mastectomy to remove the entire breast. In treating Paget’s disease, the nipple and areola are removed. Many factors are considered when determining the type of surgery that will be recommended, including the size and extent of the DCIS growth, and whether the patient has any family history of breast cancer or BRCA gene mutations. During a mastectomy, the doctor may also remove one or more lymph nodes to be analyzed in a lab for signs of cancer.
Radiation therapy treatments often follow breast-conserving surgery to destroy remaining cancer cells, though it’s not usually required after a mastectomy. Stage 0 breast cancer treatment doesn’t typically include chemotherapy.
If the abnormal cells are hormone receptor-positive, the next step may involve long-term treatment with a hormone-based drug. This medication, which is typically taken for five years, is designed to reduce the chances of cancer recurring or metastatic breast cancer.
Stage 1 breast cancer is more advanced than stage 0 and has spread farther out from the tissue where it originated. It’s classified as either stage 1A or 1B.
In stage 1A, the tumor measures 2 centimeters (cm) or smaller (about the size of a pea) and has not spread outside the breast.
In stage 1B breast cancers, either a small tumor has been found in the breast, measuring 2 cm or less, and small clusters of cancer cells measuring no more than 2 millimeters (mm) have been found in the lymph nodes; or no tumor has been found in the breast but small clusters of cancer cells (measuring no more than 2 mm) have been detected in the lymph nodes.
The care team may use a variety of imaging tests during diagnosis. In some cases, a mammogram may detect stage 1 breast cancer, while a breast ultrasound may be needed in other instances.
Breast cancer symptoms at stage 1 may include:
Treatment for stage 1 breast cancer typically includes:
Some treatments are used in a specific order to either shrink a tumor before surgery or to minimize the risk of cancer recurrence after surgery. Treatments given before surgery are called neoadjuvant therapies, while post-surgical treatments are called adjuvant therapies.
Stage 1 breast cancer surgery typically includes removing and testing one or more lymph nodes to see whether the cancer has spread.
How long the patient is in treatment for stage 1 breast cancer depends on the specific treatment plan selected. In general, treatment may last for about six months, but some patients continue taking medications for years to prevent cancer recurrence.
The survival rate for stage 1A breast cancer may be slightly higher than for stage 1B. However, all women with stage 1 breast cancer are considered to have a good prognosis.
In addition to surgery and radiation therapy, stage 1 breast cancer treatment may require chemotherapy, powerful drugs that attack all fast-growing cells in the body. In the past, almost all patients had chemotherapy. Today, the doctor may perform gene tests to help determine whether chemotherapy is likely to benefit the patient, or if it’s not necessary because the cancer isn’t likely to recur after surgery and other treatment.
Chemotherapy may or may not be used along with other drugs such as hormone therapy, targeted therapy and/or immunotherapy. The care team will determine which options may be most appropriate by examining the cancer’s specific characteristics. Patients typically take these drugs after surgery to kill the primary cancer.
When cancer spreads beyond the area where it originally developed, it’s called metastatic breast cancer. Breast cancers found in early stages, especially DCIS, are less likely to metastasize or come back after treatment, but it’s not possible to say for sure.
Breast cancers caught early have a very positive prognosis. According to the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) Program, 99 percent of patients with cancers diagnosed when still confined to the breast are alive at least five years later.