Benign diseases of the breast: An overview

Updated: Aug 12, 2018

Before we delve into breast disease, let's refresh our memory of how a benign duct and acinus look. These are the two components that make up the terminal duct lobular unit (TDLU). For a more in-depth review of breast histology, go read my "Breast basics" post.

Commonly encountered benign breast diseases include fibrocystic changes, fibroadenomas/phyllodes tumors, inflammation/mastitis, intraductal papillomas and fat necrosis. We will go into more details of each of these entities in separate posts.

Benign breast diseases can be broken down into three major categories:

1. Non-proliferative lesions

2. Proliferative lesions

3. Proliferative lesions WITH atypia

Non-proliferative breast lesions do NOT have an increased risk of developing breast cancer. Their lifetime risk is the same as the general population (~3%). There may be mild hyperplasia present, but these changes in the breast are very benign and often due to the aging process, inflammation or chronic irritation. Beware though- apocrine and squamous metaplasia can look pretty ugly sometimes!

In contrast to NON-proliferative lesions, those classified as proliferative breast disease (containing an increased number of epithelial cells) are 1.5 to 2 times INCREASED RISK FOR BREAST CANCER (7% overall)!

Atypical ductal or lobular hyperplasia carry a significantly higher risk for developing breast cancer. They are four to five times more likely to develop cancer compared to the general population; approximately 17% lifetime risk! These lesions will be discussed in greater detail in the upcoming sections on ductal and lobular proliferative breast disease.


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These posts contain high yield information collected from various educational resources including textbooks, journal articles, educational websites and more. They are intended for educational use only and should NOT be taken as medical advice. I strongly believe the spreading of knowledge and depth of learned information should be encouraged in today's society rather than coveted. Membership is required to view these posts  and should be used solely for educational purposes only.