What is Breast Cancer?

Women with benign breast lumps, especially those that increase cancer risk, should consult their healthcare provider and follow recommended screening guidelines.

Breast cancer is a malignant (cancerous) tumor that starts from cells of the breast, mostly occurring in women but can also occur in men.

A woman’s breast is made up of glands that make breast milk (lobules), ducts (tubes that carry milk from lobules to nipple), fatty and connective tissue, blood vessels, and lymph vessels.

Most breast cancers begin in the cells that line the ducts (ductal cancer), some begin in the lobules (lobular cancer), and the rest in other tissues.

Lymph vessels are channels that carry lymph fluid (containing immune cells and waste) and most breast lymph vessels lead to lymph nodes under the arm called axillary nodes.

If breast cancer cells reach the underarm lymph nodes and continue to grow, they can cause the nodes to swell and are more likely to spread to other organs.

Most breast lumps are benign, meaning they are not cancer, do not spread outside the breast, and are not life-threatening.

Some benign breast lumps can increase a woman’s risk of getting breast cancer.

Fibrocystic changes refer to cysts (fluid-filled sacs) and fibrosis (scar-like tissue) that can cause swelling, pain, lumpiness, and sometimes nipple discharge.

Carcinoma in situ refers to an early stage cancer confined to the place where it began, such as the ducts or lobules, and has not spread to breast tissue or other organs.

DCIS is the most common type of noninvasive breast cancer, confined to the ducts and not spread into breast tissue; nearly all women with DCIS can be cured.

The best way to find DCIS early is with a mammogram.

LCIS begins in the milk-making glands but does not go through the wall of lobules. It is not a true cancer but increases a woman's risk of developing cancer later.

Having LCIS means higher future breast cancer risk, so women with LCIS should follow breast cancer screening guidelines.

IDC is the most common breast cancer, starting in a milk duct, breaking through into breast tissue, and potentially spreading to other parts of the body. It accounts for about 80% of invasive breast cancers.

ILC starts in the milk glands or lobules and can spread to other body parts. About 10% of invasive breast cancers are of this type.

Yes, there are several other less common types of breast cancer not detailed in this sheet.

Information about breast cancer in men can be found at the American Cancer Society's page: http://www.cancer.org/cancer/breastcancerinmen/index

Yes, men can get breast cancer, though it is much more common in women.

The information is adapted from the American Cancer Society's website, specifically their breast cancer section.

Most breast cancers start in ducts or lobules, but some can begin in other tissues of the breast.

Women with benign breast lumps, especially those that increase cancer risk, should consult their healthcare provider and follow recommended screening guidelines.

Breast cancer is a malignant (cancerous) tumor that starts from cells of the breast, mostly occurring in women but can also occur in men.