Breasts are composed of lobules, which are glands that produce milk in women; ducts, which are tiny tubes that transport milk from the lobules to the nipple; and stroma, which is the name given to the group of fatty and connective tissue that surrounds the lymph nodes and blood vessels. The physiognomy of the male breast is similar to the female, but men’s bodies do not include lobules, while the smaller amounts of female sex hormones make their breasts grow very little during adolescence, unlike women.

Breast tissue density is a characteristic of the breast. It can be higher or lower based on the results of a mammogram, and it can have an impact on a woman’s health — including the probability of developing breast cancer. The malignant disease is characterized by an uncontrollable growth of cells in the breast. About one in every eight women in the U.S. — about 12 percent of all U.S. women — will develop breast cancer in their lifetime, while the risk for men is much less — about one in 1,000.

What Does Breast Tissue Density Mean?

“Breast density is seen only on mammograms. Some women think that because their breasts are firm, they are dense. But breast density isn’t based on how your breasts feel. It’s not related to breast size or firmness,” according to the American Cancer Society’s “Breast Density and Your Mammogram Report.”

“Radiologists are the doctors who ‘read’ x-rays like mammograms,” the ACA report says. “They check your mammogram for abnormal areas, and also look at breast density. There are four categories of breast density. They go from almost all fatty tissue to extremely dense tissue with very little fat. The radiologist decides which of the four categories best describes how dense your breasts are.”

A classification of high breast tissue density is when the amount of fatty tissue is very low compared to the amount of non-fatty tissue. This means that dense breasts have more gland tissue, ducts, and stroma than fat tissue, while the opposite happens for low breast tissue density.

The categories defined by the Breast Imaging Reporting and Database Systems (BI-RADS) range from mostly fatty, to scattered density, consistent density, and extremely dense. Breast tissue density is inherited, which is why mothers and daughters tend to register the same density.

How Does Breast Tissue Density Impact Health?

Women with high breast tissue density or with dense breasts have a higher risk of developing breast cancer than women with less-dense breasts. In women with dense breasts, it is often difficult to detect breast cancer in a mammogram because dense tissue and tumors appear white. But because physicians are aware of this, there are recommendations that can be made for women to prevent severe health problems. Women with dense breasts should adopt lifestyle options like maintaining a healthy weight, exercising, limiting alcohol consumption, eating healthy food, and not smoking. These are just a few recommendations that can help decrease the risk.

Also, it is important for women to be closely followed by their physician and perform a monthly breast self-exam, an annual breast exam by the doctor, and a digital mammogram every year starting at the age of 40.

Also important is that women know other risk factors to avoid potential triggers. “If your mammogram report says that you have dense breast tissue, talk with your provider about what that means for you. Be sure that your doctor or nurse knows your medical history and whether there’s anything in your history that increases your risk for getting breast cancer,” says the American Cancer Society. “Any woman who’s already in a high-risk group (based on gene mutations, a strong family history of breast cancer, or other factors) should have an MRI along with her yearly mammogram.”

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