What is Breast Cancer?

What is Breast Cancer?

Breast cancer occurs when the cells in the breast tissue multiply and grow abnormally. The two main types of breast cancer are ductal carcinoma and lobular carcinoma. Though uncommon, additional types of breast cancer can be present in other areas of the breast.

  • Ductal carcinoma - This is the most common of breast cancer and starts in the milk ducts
  • Lobular carcinoma - This type of breast cancer is in reference to the lobules–the area of the breast that produces the milk

If breast cancer is left untreated, it can metastasize (spread and grow in another part of the body).

Types of Breast Cancer


Doctors determine the types of breast cancers according to which areas they develop and spread.

Breast cancer is a type of carcinoma that originates in the breast tissue and is considered an adenocarcinoma (cancerous cells that line organs such as breasts, lungs, prostate, colon, esophagus, or pancreas).

The earliest stage of ductal carcinoma (cancer that starts in the milk ducts) is carcinoma in situ (DCIS). The term "in situ" refers to the cancer being limited to the milk ducts. This form of breast cancer is also noninvasive, meaning it is unlikely to spread to other body areas. Ductal carcinoma is highly curable and occurs in about 1 in 5 people who are diagnosed with breast cancer.

Another type of ductal carcinoma is invasive ductal carcinoma (IDC). Considered to be the most common type of breast cancer, IDC affects about 80% of those diagnosed with breast cancer. The word "invasive" refers to cancer spreading beyond the milk ducts where it originated.

Invasive ductal carcinomais divided into subtypes:

  • Medullary carcinoma - A rare, invasive breast cancer affecting less than 5% of diagnosed breast cancers. Medullary carcinoma is named because it resembles the gray matter tissue of the brain's medulla.
  • Mucinous carcinoma - Also known as colloid carcinoma, this type of cancer affects about 2% of breast cancers. It occurs when the "mucin" contained in mucus becomes too abundant surrounding a cell.
  • Tubular carcinoma - This type of breast cancer grows slowly and is treatable. It gets its name from the tube-shaped formations inside the cancer cells. This type of cancer accounts for 1-2% of invasive breast cancers.
  • Papillary carcinoma - Named for the papules (finger-like growths) that poke through the cancer cells, this type of breast cancer affects about 1% of cases. The majority of those affected are older women.
  • Cribriform carcinoma - This type of breast cancer is rare and affects about 5-6% of invasive breast cancers. It is recognized by the distinct pattern of holes in between the cancer cells.

Lobular carcinoma, also known as infiltrating lobular carcinoma (ILC),is the second most common invasive cancer affecting about 10% of invasive breast cancers. In this type of cancer, a missing protein means cells have trouble "sticking together." As a result, this cancer can spread through breast tissue. If ILC spreads to the lymph nodes, it is transmitted to other body parts.

Inflammatory breast cancer is a rare, rapidly developing type of breast cancer. The affected breast often becomes swollen, red, and tender (and sometimes looks like an orange peel called peau d'orange). Inflammatory breast cancer forms when the lymphatic vessels located in the breast skin are blocked by cancer cells. Inflammatory breast cancer originates from nearby tissue, usually the point of origin, and often advances to lymph nodes. Researchers are not sure what may cause inflammatory breast cancer.

Paget's disease of the breast is a rare form of breast cancer. It causes the skin around the nipple and areola to become scaly and thick, similar to eczema. This type of cancer usually forms in the tissue behind the nipple. Paget's disease of the breast is considered invasive cancer since it spreads to surrounding tissue.

Metastatic breast cancer, classified as Stage IV breast cancer, means that breast cancer has spread to other parts of the body, including the brain, liver, lungs, and bones. Metastatic breast cancer occurs when healthy breast tissue cells are invaded by cancer cells. They further replicate themselves into more abnormal cells. These abnormal cells enter the circulatory or lymph system causing cancer cells to travel to lymph or blood vessels. These cells are then carried to other parts of the body. The cancer cells cease traveling through the body and begin to infect the surrounding tissue.

HR+ breast cancer - Another way breast cancer is categorized is based on three receptors evaluated at diagnosis: ER, PR, and HER-2. A tumor contains hormone receptors, referred to as hormone receptor-positive or HR+. This means that the tumor needs estrogen and/or progesterone to grow. Approximately 80% of breast cancer cases are HR+. If a tumor does not contain hormone receptors, it is called hormone receptor-negative or HR-.

HER2+ breast cancer - All breast cells contain HER2 proteins, receptors controlling how the cells grow and divide. If breast tissue has extra HER2 receptors (overexpression), these breast cells can multiply too quickly, resulting in uncontrolled cell growth leading to a tumor.

Triple-negative breast cancer – In this form of breast cancer, estrogen, progesterone, and the HER2/neu gene, are not present in the cancerous tumor. The cancer is may be treated with chemotherapy, immunotherapy, surgery, and radiation therapy. If caught and treated early, this type of cancer responds well to chemotherapy.

Stages of Breast Cancer


Once a person is diagnosed with breast cancer, the doctor will determine whether the cancer has spread to other body parts. This process is called staging. After the results are examined, the doctor can determine how far the cancer has spread and what course of treatment will provide the best results.

Breast cancer is classified into four stages using Roman numerals—the greater the numeral, the more invasive a cancer is determined to be. This staging system is updated and improved as more advanced treatments are developed.

Stage 0

  • Noninvasive

Stage I

  • Tumor: Very small, confined to inside the glands; tumor can be more than 2 centimeters
  • Lymph nodes: No cancer present
  • Spreading: confined to breast area—has not spread to other tissue

Stage II

  • Tumor: 2-5 centimeters
  • Lymph nodes: Can possibly be affected by cancer but not always
  • Spreading: Confined to the breast tissue area—has not spread outside

Stage III

  • Tumor: 5 centimeters or larger; has spread to muscle and skin
  • Lymph nodes: Often affected by cancer, but not always
  • Spreading: Confined to breast area—not outside

Stage IV

  • Tumor: Any size
  • Lymph nodes: May be affected by cancer but not a requirement
  • Spreading: Cancer has spread outside the breast area to other parts of the body

Stages of breast cancer

Signs & Symptoms of Breast Cancer


Symptoms and signs of breast cancer differ between people and the type of breast cancer affecting them. Some patients may show no signs, and breast cancer is discovered during a routine mammogram. Symptoms of other conditions can resemble those associated with breast cancer. However, general warning signs of breast cancer include:

  • Lump in the breast or underarm
  • Thickening or swelling of the breast
  • Dimpling of the breast skin
  • Red, flaky skin surrounding the nipple area
  • Discharge from the nipple (including blood)
  • Pain in the breast
  • Any change to the breast that causes you concern

If you are experiencing these types of breast cancer symptoms, contact your doctor immediately. Only a doctor can determine the proper tests to conduct when searching for breast cancer. The expert oncologists at NewYork-Presbyterian are experienced in the latest technology and treatments. With convenient offices located throughout the New York area, we’re here to help and answer your questions.

What Causes Breast Cancer?


Doctors are not exactly sure what causes breast cancer. Each type of breast cancer cell involves normal breast cells being altered into abnormal cells and invading nearby healthy cells, thereby replicating the process.

Risk factors that can contribute to the development of breast cancer cells include:

  • Age - People over 55 years old are at greater risk for developing breast cancer
  • Sex - Women are more likely to develop breast cancer; however rare, men also can develop breast cancer
  • Family history - People with close family members diagnosed with breast cancer have a higher risk of developing this type of cancer. About 5-10% of breast cancers stem from an abnormal gene inherited from a parent. Genetic testing can determine if you carry this gene.
  • Genetics Some people are born with genes that make them predisposed to developing breast cancer, despite not having a known family history of breast cancer.
  • Alcohol - Research has concluded that drinking alcohol does increase your risk for developing several types of breast cancer
  • Weight - There is a correlation between being overweight/obese and an increased risk of breast cancer and reoccurring breast cancer
  • Radiation - If you have received radiation therapy, particularly to your chest, neck, or head, you have an increased risk of developing breast cancer
  • Hormone replacement therapy - People who use hormone replacement therapy (HRT) have an increased risk of developing breast cancer

There are other circumstances that can lead to breast cancer, including environmental reasons. If you are concerned that you have been exposed to breast cancer risk factors, contact a healthcare provider.

How to Prevent Breast Cancer?


There is no certain way to avoid getting breast cancer, but there are sensible suggestions that you can follow to lead an overall healthier life and reduce your risk.

Prevention is always the best course of action—therefore, limit alcohol consumption, exercise, maintain a healthy weight, and reduce hormone therapy if possible. Most importantly, maintain your mammogram appointments and do not skip regular check-ups. Early detection of breast cancer is your best defense against the progression of this disease. For some high-risk patients, preventive endocrine therapy is administered in one of our high-risk clinics.


Metastatic breast cancer is Stage IV cancer that has spread to areas outside the breast tissue.

Going for your yearly mammograms is the most reliable way to spot breast cancer early. These tests can help your doctor discover breast cancer before symptoms occur; early detection can lower your risk of cancer progressing.

Aside from the various forms of skin cancer, breast cancer is the most common form of cancer in women.

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