What Is Breast Cancer?

If you've received a diagnosis of cancer in one or both of your breasts, you should know that you are not alone. Breast cancer is the most common form of cancer in women, according to the American Cancer Society, which estimates about 207,090 cases of invasive breast cancer and 39,840 deaths from breast cancer in 2010. Over the course of a woman's life, she has a 1 in 8 chance of getting the disease. Breast cancer in men is rare, with an estimated 1,910 cases diagnosed in 2010. 

In breast cancer, malignant (cancer) cells form in the tissue of the breast. These cells are different from normal, healthy cells. Normally, cells grow in an orderly manner. But cancer cells become abnormal and grow out of control.

Sometimes breast cancer develops slowly. Other times, the cancer is aggressive and tumors develop quickly. Prompt attention in this disease is necessary because cancer cells can break away and travel through the bloodstream to damage other parts of the body. The spread of cancer to another part of the body is called metastasis.

Structure of the Breast 

Each breast has 15 to 20 sections called lobes. Each lobe has several smaller sections called lobules. Lobules end in dozens of tiny bulbs that can produce milk. The lobes, lobules, and bulbs are linked by thin tubes called ducts. These ducts lead to the nipple in the center of the breast. The breasts are glands that make and release milk in women after pregnancy.

 

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Each breast also has blood vessels and lymph vessels. These vessels carry excess fluid out of your breast. The fluid is called lymph. The lymph vessels lead to small bean-shaped structures called lymph nodes. Clusters of lymph nodes are found in the armpit (called the axilla), above the collarbone, and in the chest.

What are the different types of breast cancer?

Below are the different kinds of breast cancer. It is not unusual to have a tumor with invasive and noninvasive components.

Adenocarcinoma - Most breast cancers begin in the ducts or lobules of the breast. These are glandular tissues. The two most common types of breast adenocarcinomas are ductal carcinomas and lobular carcinomas.

Ductal carcinoma in situ (DCIS) (also known as intraductal carcinoma or noninvasive breast cancer) - This early-stage breast cancer is confined to the ducts and has not invaded surrounding tissue. This is also known as stage 0 breast cancer, or pre-invasive breast cancer.

Infiltrating (or invasive) ductal carcinoma (IDC) - This type is the most common of all invasive breast cancers. It begins in a duct, or milk passage; breaks through the lining of the duct; and invades the fatty tissue of the breast. About 70 percent to 80 percent of all newly diagnosed cases of invasive breast cancer are this type.

Infiltrating (or invasive) lobular carcinoma (ILC) - This type starts in the ends of the ducts or in the lobules. It accounts for about 10 percent of invasive breast cancers. It can be more difficult to detect by a mammogram than invasive ductal carcinoma.

Inflammatory breast cancer - This is a rare form of breast cancer (only about 1 percent to 3 percent of all breast cancers). In this type, the skin of the breast looks red, inflamed, and pitted because the skin lymph vessels are blocked by cancer.

 

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Lobular carcinoma in situ (LCIS) (also called lobular neoplasia) - Is considered a sign of an increased risk of breast cancer. It starts in the milk-producing glands, but does not break through the lining of the lobule.

Medullary carcinoma - This is a type of infiltrating, or invasive breast cancer, that accounts for about 5 percent of breast cancers. In this type, there is a well-defined boundary between tumor tissue and the normal tissue.

Invasive Paget's disease of the nipple - This is a rare form of breast cancer (less than 1 percent of all cases of breast cancer). It starts with an itchy, eczema-like rash around the nipple, which is associated with an underlying malignancy.

Phyllodes tumor - This is a rare form of breast cancer that develops in the connective tissue of the breast (stroma). This is different than carcinomas, which start in the ducts or lobules. These types of tumors are usually benign, but in rare instances they may be malignant.

Tubular carcinoma - This is a rare kind of invasive (infiltrating) breast carcinoma. It is named for the way the cells look under the microscope. Generally, this form is associated with a very good prognosis.