Stage 0 Breast Cancer: What to Know About the Earliest Stage of Breast Cancer

Over 250,000 women are diagnosed with breast cancer every year. About 1 in 8 women will get invasive breast cancer at some point in their lifetime. But stage 0 breast cancer isn’t invasive. It means the tumor is contained, with no evidence of spread to surrounding areas. 

In this guide, we provide a general overview of how stage 0 breast cancer is diagnosed, the treatments specific to this stage, and follow-up care to prevent recurrence. We’ll also review different types of “pre-breast cancer” conditions that come before stage 0.

What is stage 0 breast cancer?

Stage 0 breast cancer is noninvasive breast cancer. It describes a cancer that hasn’t invaded any tissue beyond the area where it started. This is the earliest stage of breast cancer. It’s also called carcinoma in situ. 

Stage 0 breast cancer means there’s no evidence of spread to surrounding breast tissue, lymph nodes, or distant areas of your body. But there’s still variability within stage 0. The cancer can: 

• Be any size

• Be any grade

• Have any combination of hormone receptor status (Some breast cancers have receptors that make them grow in response to hormones and other molecules.)

There are two types of breast cancer that can be classified as stage 0: 

• Ductal carcinoma in situ (DCIS)

• Paget’s disease of the nipple

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Lobular carcinoma in situ (LCIS) used to be classified as stage 0 breast cancer, but this is no longer the case. It’s now considered to be “pre-breast cancer.”

Ductal carcinoma in situ (DCIS)

The most common type of stage 0 breast cancer is DCIS. DCIS is cancer located in the breast duct and nowhere else. About 1 in 5 newly diagnosed breast cancers will be DCIS. While DCIS does have a risk of progressing to higher breast-cancer stages (called invasive ductal carcinoma), many of these cancers will remain stage 0.

Paget’s disease 

Paget’s disease is a rare form of breast cancer that affects the nipple. It may also be stage 0. It accounts for less than 3% of all breast cancers. The majority of people with Paget’s disease have underlying DCIS. Paget’s disease can become invasive and progress beyond stage 0. 

Lobular carcinoma in situ (LCIS)

LCIS is defined as abnormal cells located in the breast lobule, more commonly known as the milk glands. It makes up 1.5% to 2.5% of all biopsied breast masses. While LCIS doesn’t typically progress to later-stage cancer, it does increase someone’s risk of developing invasive lobular carcinoma.

How does breast cancer start?

Breast cancer begins when breast cells develop mutations that allow the cells to divide more than they should. If these cells aren’t kept in check, they multiply enough to form a tumor. 

Cancer cells can then break off from the tumor and travel through your lymphatic system. This is how they spread to local lymph nodes. Lymph nodes are small collections of immune system tissue. They often get bigger when responding to an infection or cancer. Lymph nodes in the armpit (axilla), under the breastbone (sternum), and around the collarbone (clavicle) are some of the first places that breast cancer cells can spread. 

Not all mutations that affect cell replication lead to cancer. Sometimes, those mutations increase the number of cells without actually becoming cancerous. This is known as pre-breast cancer, which includes two main categories:

• Lobular carcinoma in sit (LCIS), described above

• A condition called atypical hyperplasia 

While atypical hyperplasia isn’t cancer, it does increase the risk of being diagnosed with breast cancer in the future.

Breast cancer staging

There are five stages of breast cancer: 

• Stage 0

• Stage 1 (I)

• Stage 2 (II)

• Stage 3 (III)

• Stage 4 (IV)

Breast cancer staging is complicated because there are multiple different approaches. 

Regardless of the method, staging generally takes into account three main factors:

• The anatomy of the cancer (how far the cancer has spread)

• The receptor status of the cancer (which types of receptors are present on the cancer cells)

• The grade of the cancer (how quickly the cancer is growing)

Anatomic staging (TNM)

Anatomic staging is the most common staging method. It focuses on how far the cancer has spread. This is also referred to as TNM staging: 

• “T” stands for tumor size: Larger tumors tend to be staged higher than smaller tumors. The tumor is initially measured by imaging studies like mammography, ultrasound, or MRI.

• “N” stands for nodes: If the cancer has spread to lymph nodes, this generally leads to a higher stage. This can be evaluated by physical exam, imaging (usually through ultrasound), or biopsy. 

• “M” stands for metastasis: This refers to cancer that has spread to distant tissues or organs. These are usually evaluated by CT scan, bone scan, or a PET/CT scan. Any sign of metastasis means it is stage 4 breast cancer. 

Receptor status

Breast cancer staging also depends on the types of receptors on the surface of the cancer cells. A specialist called a pathologist can perform tests on a sample of breast cancer cells to determine which receptors are present:

• Hormone receptor-positive breast cancer means there are estrogen receptors (ER) and/or progesterone receptors (PR) on the surface of the cancer cells. Estrogen and progesterone are hormones normally found in your body, and these hormones may stimulate the growth of breast cancer cells that contain these receptors. 

• HER2-positive breast cancer cells contain the molecular marker HER2 in unusually high levels. Cells with high quantities of HER2 can experience abnormally increased growth that can lead to cancer. HER2 status isn’t usually a consideration in stage 0 breast cancer.

Breast cancer can be classified as hormone receptor-positive or -negative, HER2-positive or -negative, or “triple-negative”. This means the cancer is ER-negative, PR-negative, and HER2-negative.

Cancer grade

In addition to testing for certain receptors, a pathologist also notes the appearance of the cancer cells under the microscope. This is known as cancer cell grade, which provides information about how quickly the cancer cells are multiplying. Higher-grade cells appear more abnormal and can also lead to a higher cancer stage.

Symptoms of stage 0 breast cancer

Stage 0 breast cancer, especially DCIS, usually doesn’t have any symptoms. Nearly all cases are diagnosed with a mammogram. If symptoms are present, they may include a breast lump or abnormal nipple discharge. 

Paget’s disease of the nipple is a little different and is more likely than DCIS to be associated with symptoms. This type of cancer usually presents with redness, swelling, and possible ulceration around the nipple. 

Diagnosis of stage 0 breast cancer

A stage 0 breast cancer diagnosis usually starts with an abnormal finding on a mammogram. Not all abnormalities on a mammogram are cancer. But when something looks abnormal, it usually means more tests are needed to figure out what it is.

The next test could be an ultrasound to take a closer look at the suspicious area. Or, the next test could be a breast biopsy. A breast biopsy is a minor procedure that uses a needle to collect cells from the area in the breast that could be a tumor. Some people worry that a biopsy can potentially spread cancer cells, but there’s no evidence that this is true. After the procedure, a pathologist then observes these cells under a microscope and determines whether they are cancerous or non-cancerous. 

No matter how the diagnosis begins, a biopsy determines whether or not it’s cancer. 

Treatment of stage 0 breast cancer

The goal of treatment for stage 0 is to cure the cancer. Every person will have a treatment plan designed specifically for them and the specific characteristics of their cancer. 

Breast cancer treatment is a team sport. Multiple specialists are usually involved in the treatment process. This team can include: 

• A breast surgeon to remove the tumor

• A radiation oncologist to administer radiation after surgery

• A breast oncologist, if hormone-blocking treatment is indicated

Breast cancer treatment generally falls under two main categories:

• Local treatment: The goal of local treatment is to treat breast cancer at the source. Local treatment can involve surgery and/or radiation. This is the main type of treatment for stage 0 cancer.

• Systemic treatment: This type of treatment delivers medicine to your whole body. It’s better for cancers that have spread throughout the breast, lymph nodes, or the rest of your body, so it has less of a role in stage 0 cancer. 

Surgery

The two kinds of local treatment are surgery and radiation. 

Surgery can include a lumpectomy or mastectomy. A lumpectomy removes the tumor along with some surrounding breast tissue. A mastectomy removes the entire affected breast. The best surgical approach is determined by the size of your tumor and how much space it takes up in your breast.

During surgery, a breast surgeon can also check the surrounding lymph nodes for cancer. They do this with a sentinel lymph node biopsy. In this procedure, the surgeon injects blue dye near the tumor to tag the cancer cells. They then observe which lymph nodes are in the path of the growing cancer cells. This helps identify which lymph nodes are most at risk for cancer spread. The surgeon then removes those lymph nodes and tests them for any cancer involvement. 

Radiation

Surgery is often followed by radiation. Radiation therapy directs X-rays at cancer cells, which damages and kills them. It’s used after surgery to make sure no cancer cells were left behind after the main tumor was removed. This approach also allows the initial surgery to be less invasive. 

A lumpectomy followed by radiation therapy is known as breast-conserving therapy. This is a more common approach than a total mastectomy in stage 0 breast cancer.

In addition to local therapy, systemic treatment may also be offered. This often depends on the hormone receptor status of the cancer cells and the risk of cancer recurrence after the cancer is treated. 

Systemic treatment

Systemic treatment includes treatments like chemotherapy and hormone therapy. It’s less common in stage 0 breast cancer because the cancer cells haven’t spread to other parts of your body. 

Stage 0 cancer is usually cured with localized therapy, and chemotherapy isn’t necessary. 

Hormone therapy may sometimes be used if the cancer cells are positive for hormone receptors. Hormone therapy may help to prevent a second breast cancer later on. So, it may be given for several years after the initial treatment. This involves taking an oral selective estrogen receptor modulator (SERM) or an aromatase inhibitor (AI). 

How do you prevent breast cancer recurrence after treatment?

One study estimated the risk of recurrence with DCIS to be less than 20%. But this is based on averages. The risk of recurrence can vary from person to person. It depends on: 

• The stage of breast cancer when diagnosed

• Characteristics of the tumor

• The initial treatment of the cancer

• Individual risk factors 

There are some breast cancer risk factors that you can’t change or avoid. These include:

• Genetics (like the BRCA or PALB2 gene) or family history of breast or ovarian cancer

• Anything that increases someone’s exposure to estrogen (such as female sex, the age of first menstruation or menopause, and prior pregnancies)

• Advancing age

The good news is that there are also risk factors for breast cancer recurrence that you can change. These include:

• Hormonal medications (especially hormone replacement therapy)

• Increased alcohol intake

• Increased dietary fat intake

• Increased body weight (although it’s important to note that someone’s weight isn’t entirely within their control)

• Lack of exercise

One of the best ways to prevent recurrence is follow-up mammography. This is typically recommended more frequently than for the general population.

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Written by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

Reviewed by:

Nicholas McAndrew, MD, MSCE

Dr. Nicholas McAndrew is a hematologist oncologist at the UCLA David Geffen School of Medicine in Los Angeles. Dr. McAndrew received his medical degree from the Perelman School of Medicine at the University of Pennsylvania, and completed both his internal medicine residency and his hematology/oncology fellowship at the Hospital of the University of Pennsylvania.

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