What is Breast Cancer?

Breast cancer occurs when cells in the breast divide and begin to grow beyond their normal control. The cells form a tumor, which tends to grow slowly. Though often seen by an x-ray, tumors large enough to feel as a lump may have been growing for as long as 10 years.

According to the National Cancer Institute, In the United States, breast cancer is the second most common cancer in women after skin cancer. Annually, there are about 2,300 new cases of breast cancer in men and about 230,000 new cases in women.

The main risk factors for breast cancer are non-modifiable such as gender, age, race and family history. Other factors include modifiable lifestyle behaviors such as smoking, drinking, and diet. Maintaining a healthy weight, being physically active and limiting alcohol and tobacco intake can help reduce the risk of breast cancer.


Ductal Carcinoma in situ (DCIS) – noninvasive; cancer cells are contained within the lining of the breast milk duct. About 1 in 5 new breast cancer cases will be DCIS and nearly all women at this early stage can be cured.

Invasive Ductal Carcinoma – The most common type of breast cancer, cells have begun to invade the surrounding fatty tissue of the breast and can spread to other parts of the body through lymph nodes or bloodstream.

Metastatic Breast Cancer – Known as stage IV or advanced breast cancer, the disease has spread beyond the breast and into organs. Even in another part of the body, it is still considered and treated as breast cancer. For example, breast cancer that has spread to the lungs is still breast cancer, not lung cancer and is treated with breast cancer drugs.

Less common types of breast cancer


With the use of regular mammography screening, most breast cancer cases in the U.S. are found at an early stage. Diagnosis can also be detected via an ultrasound, MRI, and biopsy. However, it is important to perform self-breast exams as the symptoms of breast cancer are not the same for all women.

Symptoms vary widely, from lumps to swelling to skin changes, and sometimes a lack thereof. The most common signs of breast cancer are:

  • swelling of all or part of the breast
  • skin irritation or dimpling
  • breast pain
  •  nipple pain or the nipple turning inward
  • redness, scaliness, or thickening of the nipple or breast skin
  •  a nipple discharge other than breast milk
  • a lump in the breast or underarm area (all lumps should be investigated by a health care provider, but not all lumps are cancerous)


Once diagnosed, the health care provider will determine staging which helps determine how serious the cancer is and how best to treat it. Stages are based on several factors including the size of the tumor, number of lymph nodes affected, if the cancer is invasive or non-invasive, and if the cancer has spread to other parts of the body.

Stage 0

Early detection of breast cancer development, the disease is confined to a very limited area and have not invaded deeper into the surrounding fatty breast tissue.

Stage 1A & 1B

Still an earlier stage, the tumor is growing but has not spread to lymph nodes or other parts of the body.

Stage 2A & 2B

An earlier stage, the tumor has grown 2-5 cm and may or may not have begun to spread. This stage is generally effectively treated.

Stage 3A, 3B & 3C

The tumor either cannot be found, is less than or larger than 5 cm. Depending on the stage, it has spread to up to 10 or more lymph nodes but has not spread to other parts of the body.

Stage 4

The tumor can be any size and may or may not have spread to nearby lymph nodes. It has spread to distant organs or to lymph nodes far from the breast, commonly spreading to the bones, liver, brain, or lungs.

More detail on breast cancer stages


A treatment plan is developed with a health care provider based on both your medical and personal choices. In order to get rid of cancer and keep it from coming back, treatment includes some combination of:


Removes the entire tumor from the breast via lumpectomy (wide incision) or mastectomy (removal of the breast).

Radiation therapy

Uses targeted, high-energy rays to kill cancer cells on most women who have DCIS or early stage breast cancer. There are a variety of techniques to deliver this treatment which is based on the individual needs of each patient.


Drugs used to kill or disable cancer cells based on tumor stage, tumor characteristics and other factors such as age and overall health.

Hormone therapy

Used to slow or stop the growth of hormone receptor-positive tumors by preventing the cancer cells from getting the hormones they need to grow.

Targeted therapy

Drug designed to attack a certain molecular agent or pathway involved in the development of cancer with little harm to other cells. However, many people cannot use these drugs as they only work on the cancers with the gene makeup specifically targeted.


Additional Resources:

Risk Factors & Reduction – Susan G. Koman

What’s New In Breast Cancer Research – American Cancer Society

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