Breast

The breast consists of three main components, the skin, the subcutaneous adipose tissue and the functional glandular tissue that comprises both parenchyma and stroma. The collecting ducts open at the nipple. The breast is divided into lobes, each based on a branching duct system that leads from the collecting ducts to the terminal duct-lobular units. The terminal duct-lobular units are the functional sites of milk production.

In the nipple, the stratified squamous epithelium from the surface extends into the collecting ducts for a short distance, followed by an abrupt change into glandular epithelium that is present throughout the duct and lobular system. The glandular epithelium is composed of two distinct types of cells, the secretory/luminal cells and the myoepithelial cells. In the collecting ducts the lining cells are usually columnar whereas in the acini they are usually cuboidal.

On microscopic examination, the breast is mainly composed of:

• Lobules - milk-producing glandular tissue
• Ducts - milk-collecting ducts
• Adipose tissue - milk ingredient
• Stroma - connective tissue
• Blood vessels - supply of oxygen and nutrients