Whether you, a friend, or a family member has been diagnosed with breast cancer, navigating all of the information available can be overwhelming.

Here’s a simple overview of breast cancer and its stages, followed by a breakdown of how breast cancer spreads, how it’s diagnosed, and how doctors treat it.

Breast cancer happens when cancer cells form in breast tissue. It’s one of the most common types of cancer diagnosis for women in the United States, second only to skin cancer. This disease can also affect men.

Early detection has helped with diagnosing breast cancer and improving survival rates.

The symptoms may include:

Keeping up with regular breast self-exams and mammograms can help you notice any changes as they occur. If you notice any of these symptoms, tell your doctor as soon as you can.

Your doctor identifies the stage of cancer by determining:

  • whether the cancer is invasive or noninvasive
  • the size of the tumor
  • the number of lymph nodes affected
  • the cancer’s presence in other parts of the body

Your doctor will be able to tell you more about your outlook and appropriate treatment options once the stage is determined through various tests.

The five stages of breast cancer are:

Stage 0

In stage 0, the cancer is considered noninvasive. There are two types of stage 0 breast cancer:

  • In ductal carcinoma in situ (DCIS), the cancer is found inside the lining of the milk ducts but hasn’t spread to other breast tissue.
  • While lobular carcinoma in situ (LCIS) is also classified as a stage 0 breast cancer, it isn’t actually considered cancer. Instead, it describes abnormal cells that have formed in the lobules of the breast.

Stage 0 breast cancer is highly treatable.

Stage 1

At this stage, the cancer is considered invasive but localized. Stage 1 is divided into 1A and 1B forms:

  • In stage 1A, the cancer is smaller than 2 centimeters (cm). It hasn’t spread to the surrounding lymph nodes.
  • In stage 1B, your doctor might not find a tumor in your breast, but the lymph nodes may have tiny groupings of cancer cells. These groupings measure between 0.2 and 2 millimeters (mm).

As with stage 0, stage 1 breast cancer is highly treatable.

Stage 2

The cancer is invasive in stage 2. This stage is divided into 2A and 2B:

  • In stage 2A, you may have no tumor, but the cancer has spread to your lymph nodes. Alternatively, the tumor might be less than 2 cm in size and involves the lymph nodes. Or the tumor may measure between 2 and 5 cm but doesn’t involve your lymph nodes.
  • In stage 2B, the tumor size is larger. You may be diagnosed with 2B if your tumor is between 2 to 5 cm and it has spread to four or fewer lymph nodes. Otherwise, the tumor might be bigger than 5 cm with no lymph node spread.

You may require stronger treatment than with the earlier stages. However, the outlook is still good at stage 2.

Stage 3

Your cancer is considered invasive and advanced if it reaches stage 3. It hasn’t yet spread to your other organs. This stage is divided into the subsets 3A, 3B, and 3C:

  • In stage 3A, your tumor may be smaller than 2 cm, but there are between four and nine affected lymph nodes. Tumor size at this stage may be larger than 5 cm and involve small gatherings of cells in your lymph nodes. The cancer may have also spread into the lymph nodes in your underarm and breastbone.
  • In stage 3B, the tumor can be any size. At this point, it has also spread into your breastbone or skin and affects up to nine lymph nodes.
  • In stage 3C, the cancer may have spread to over 10 lymph nodes even if no tumor is present. The lymph nodes affected may be near your collarbone, underarm, or breastbone.

Treatment options at stage 3 include:

These treatments are also offered in earlier stages. Your doctor may suggest a combination of treatments for the best outcome.

Stage 4

At stage 4, the breast cancer has metastasized. In other words, it has spread to other parts of the body. This can include one or more of the following:

  • brain
  • bones
  • lungs
  • liver

Your doctor may try a variety of treatment options, but the cancer is considered terminal at this stage.

There are several ways cancer can spread in the body.

  • Direct invasion happens when the tumor has spread to a nearby organ in the body. The cancer cells take root and begin to grow in this new area.
  • Lymphangitic spread occurs when cancer travels through the lymphatic system. Breast cancer often involves the nearby lymph nodes, so the cancer can enter the lymph circulatory system and take hold in different parts of the body.
  • Hematogenous spread moves in much the same way as lymphangitic spread but through the blood vessels. The cancer cells travel through the body and take root in remote areas and organs.

When cancer starts in the breast tissue, it may often spread to the lymph nodes before affecting other parts of the body. Breast cancer most commonly spreads to the:

  • bones
  • brain
  • liver
  • lungs

A variety of tests can detect the spread of cancer. These tests typically aren’t performed unless your doctor thinks the cancer may have spread.

Before ordering them, your doctor will evaluate your tumor size, lymph node spread, and the specific symptoms you’re having.

The most common tests include:

The type of test you end up having will depend on your medical history and symptoms. For example, if you or your doctor suspects the cancer may have spread to your abdomen, you may have an ultrasound.

CT and MRI scans can help your doctor visualize various parts of the body all at once. A PET scan can be helpful if your doctor thinks the cancer may have spread but isn’t sure where.

All of these tests are relatively noninvasive, and they shouldn’t require a hospital stay. You may be given special instructions before your test.

If you have a CT scan, for instance, you may need to drink an oral contrast agent to help outline different features inside your body.

If you have any questions or concerns, don’t hesitate to call the office conducting the test for clarification.

Stage 4 breast cancer can’t be cured. Instead, once it’s diagnosed, treatment is about extending and improving your quality of life.

The main forms of treatment for stage 4 breast cancer include:

  • chemotherapy
  • radiation therapy
  • surgery
  • hormone therapy
  • targeted therapy
  • clinical trials
  • pain management

What treatment or treatments you try will depend on the spread of your cancer, your medical history, and your personal choices. Not all treatments are right for everyone.

How breast cancer spreads depends on a number of factors and situations that are unique to your body and your cancer. Once the cancer spreads to other organs, there’s no cure.

Regardless, treatment at stage 4 can help improve your quality of life and even lengthen your life.

Your doctor is your best resource for understanding which stage of cancer you’re in and suggesting the best treatment options available to you.

If you notice a lump or other changes in your breasts, contact your doctor to make an appointment.

If you have already been diagnosed with breast cancer, tell your doctor if you experience pain, swelling, or other worrisome symptoms.

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