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A Comprehensive Guide to Breast Cancer


What is breast cancer?

Cancer occurs when changes called mutations take place in genes that regulate cell growth. The mutations let the cells divide and multiply in an uncontrolled way.

Breast cancer is cancer that develops in breast cells. Typically, the cancer forms in either the lobules or the ducts of the breast.

Lobules are the glands that produce milk, and ducts are the pathways that bring the milk from the glands to the nipple. Cancer can also occur in the fatty tissue or the fibrous connective tissue within your breast.

The uncontrolled cancer cells often invade other healthy breast tissue and can travel to the lymph nodes under the arms. The lymph nodes are a primary pathway that help the cancer cells move to other parts of the body.

See pictures and learn more about the structure of the breast.

Signs and symptoms of breast cancer on Healthline

In its early stages, breast cancer may not cause any symptoms. In many cases, a tumor may be too small to be felt, but an abnormality can still be seen on a mammogram. If a tumor can be felt, the first sign is usually a new lump in the breast that was not there before. However, not all lumps are cancer.

Each type of breast cancer can cause a variety of symptoms. Many of these symptoms are similar, but some can be different. Symptoms for the most common breast cancers include:

  • a breast lump or tissue thickening that feels different than surrounding tissue and has developed recently

  • breast pain

  • red, pitted skin over your entire breast

  • swelling in all or part of your breast

  • a nipple discharge other than breast milk

  • bloody discharge from your nipple

  • peeling, scaling, or flaking of skin on your nipple or breast

  • a sudden, unexplained change in the shape or size of your breast

  • inverted nipple

  • changes to the appearance of the skin on your breasts

  • a lump or swelling under your arm

If you have any of these symptoms, it doesn’t necessarily mean you have breast cancer. For instance, pain in your breast or a breast lump can be caused by a benign cyst. Still, if you find a lump in your breast or have other symptoms, you should see your doctor for further examination and testing. Learn more about possible symptoms of breast cancer.


Types of breast cancer


There are several types of breast cancer, and they’re broken into two main categories: “invasive” and “noninvasive,” or in situ.


While invasive cancer has spread from the breast ducts or glands to other parts of the breast, noninvasive cancer has not spread from the original tissue.


These two categories are used to describe the most common types of breast cancer, which include:

  • Ductal carcinoma in situ. Ductal carcinoma in situ (DCIS) is a noninvasive condition. With DCIS, the cancer cells are confined to the ducts in your breast and haven’t invaded the surrounding breast tissue.

  • Lobular carcinoma in situ. Lobular carcinoma in situ (LCIS) is cancer that grows in the milk-producing glands of your breast. Like DCIS, the cancer cells haven’t invaded the surrounding tissue.

  • Invasive ductal carcinoma. Invasive ductal carcinoma (IDC) is the most common type of breast cancer. This type of breast cancer begins in your breast’s milk ducts and then invades nearby tissue in the breast. Once the breast cancer has spread to the tissue outside your milk ducts, it can begin to spread to other nearby organs and tissue.

  • Invasive lobular carcinoma. Invasive lobular carcinoma (ILC) first develops in your breast’s lobules and has invaded nearby tissue.

Other, less common types of breast cancer include:

  • Paget disease of the nipple. This type of breast cancer begins in the ducts of the nipple, but as it grows, it begins to affect the skin and areola of the nipple.

  • Phyllodes tumor. This very rare type of breast cancer grows in the connective tissue of the breast. Most of these tumors are benign, but some are cancerous.

  • Angiosarcoma. This is cancer that grows on the blood vessels or lymph vessels in the breast.

The type of cancer you have determines your treatment options, as well as your likely long-term outcome.


Inflammatory breast cancer


Inflammatory breast cancer (IBC) is a rare but aggressive type of breast cancer. IBC makes up only between 1 and 5 percentTrusted Source of all breast cancer cases.


With this condition, cells block the lymph nodes near the breasts, so the lymph vessels in the breast can’t properly drain. Instead of creating a tumor, IBC causes your breast to swell, look red, and feel very warm. A cancerous breast may appear pitted and thick, like an orange peel.

IBC can be very aggressive and can progress quickly. For this reason, it’s important to call your doctor right away if you notice any symptoms.


Find out more about IBC and the symptoms it can cause.


Metastatic breast cancer Metastatic breast cancer is another name for stage 4 breast cancer. It’s breast cancer that has spread from your breast to other parts of your body, such as your bones, lungs, or liver. This is an advanced stage of breast cancer. Your oncologist (cancer doctor) will create a treatment plan with the goal of stopping the growth and spread of the tumor(s). Learn about treatment options for metastatic cancer, as well as factors that affect your outlook.

Triple-negative breast cancer Triple-negative breast cancer is another rare disease type, affecting only about 10 to 15 percentTrusted Source of people with breast cancer, according to the American Cancer Society (ACS). To be diagnosed as triple-negative breast cancer, a tumor must have all three of the following characteristics:

  • It lacks estrogen receptors. These are receptors on the cells that bind, or attach, to the hormone estrogen. If a tumor has estrogen receptors, estrogen can stimulate the cancer to grow.

  • It lacks progesterone receptors. These receptors are cells that bind to the hormone progesterone. If a tumor has progesterone receptors, progesterone can stimulate the cancer to grow.

  • It doesn’t have additional HER2 proteins on its surface. HER2 is a protein that fuels breast cancer growth.

If a tumor meets these three criteria, it’s labeled a triple-negative breast cancer. This type of breast cancer tends to grow and spread more quickly than other types of breast cancer. Triple-negative breast cancers are difficult to treat because hormonal therapy for breast cancer is not effective. Learn about treatments and survival rates for triple-negative breast cancer.

Breast cancer stages Breast cancer can be divided into stages based on the size of the tumor(s) and how much it has spread. Cancers that are large and/or have invaded nearby tissues or organs are at a higher stage than cancers that are small and/or still contained in the breast. To stage a breast cancer, doctors need to know:

  • if the cancer is invasive or noninvasive

  • how large the tumor is

  • whether the lymph nodes are involved

  • if the cancer has spread to nearby tissue or organs

Breast cancer has 5 main stages: stages 0 to 5. Stage 0 breast cancer Stage 0 is DCIS. Cancer cells in DCIS remain confined to the ducts in the breast and have not spread into nearby tissue. Stage 1 breast cancer

  • Stage 1A: The primary tumor is 2 centimeters (cm) wide or less, and the lymph nodes are not affected.

  • Stage 1B: Cancer is found in nearby lymph nodes, and either there is no tumor in the breast, or the tumor is smaller than 2 cm.

Stage 2 breast cancer

  • Stage 2A: The tumor is smaller than 2 cm and has spread to 1–3 nearby lymph nodes, or it’s between 2 and 5 cm and hasn’t spread to any lymph nodes.

  • Stage 2B: The tumor is between 2 and 5 cm and has spread to 1–3 axillary (armpit) lymph nodes, or it’s larger than 5 cm and hasn’t spread to any lymph nodes.

Stage 3 breast cancer

  • Stage 3A:

  • The cancer has spread to 4–9 axillary lymph nodes or has enlarged the internal mammary lymph nodes, and the primary tumor can be any size.

  • Tumors are greater than 5 cm, and the cancer has spread to 1–3 axillary lymph nodes or any breastbone nodes.


  • Stage 3B: A tumor has invaded the chest wall or skin and may or may not have invaded up to nine lymph nodes.

  • Stage 3C: Cancer is found in 10 or more axillary lymph nodes, lymph nodes near the collarbone, or internal mammary nodes.

Stage 4 breast cancer Stage 4 breast cancer can have a tumor of any size, and its cancer cells have spread to nearby and distant lymph nodes as well as distant organs. The testing your doctor does will determine the stage of your breast cancer, which will affect your treatment. Find out how different breast cancer stages are treated.


Male breast cancer

Although they generally have less of it, men have breast tissue just like women do. Men can develop breast cancer too, but it’s much rarer.

According to the ACSTrusted Source, breast cancer is 100 times less common in white men than in white women. Its 70 times less common in black men than in black women. That said, the breast cancer that men develop is just as serious as the breast cancer women are diagnosed with. It also has the same symptoms.