Atlas of breast cancer early detection

The breast tissue underlying the skin is composed of:

• the glandular tissue (epithelial components), and
• the adipose tissue supported by the fibrous connective tissue (stromal elements).

Normal breast tissue on mammogram and normal microscopic anatomy of glandular tissue

The glandular tissue (epithelial components)
The glandular component of an adult breast comprises 15–20 lactiferous lobes (segments) embedded in the fat and supported by the fibrous connective tissue. Each lobe is made up of 20–40 terminal duct lobular units (TDLUs), which are the functional units of the breast. Each TDLU comprises 10–100 small sacs called glandular acini, which are connected to a terminal duct. The acini and the terminal ducts produce milk. The terminal duct has an intralobular component and an extralobular component. Extralobular terminal ducts attach the lobule to the ductal system. Each lobule drains into a lactiferous duct, which converges to drain at the nipple–areolar complex. The lactiferous ducts dilate to form the ampulla (collection of lactiferous sinuses) as they converge to the nipple.