Diagnosing Breast Cancer

What is breast cancer?

Like all cancers, breast cancer is a disease in which cells develop the ability to divide and grow abnormally.  Cancer cells also have the ability to spread throughout the body, moving from their origin through the blood and lymphatic systems.  As cells grow and divide abnormally, they form masses or tumors.  When they travel to other parts of the body, they metastasize.

The breast is composed mainly of fatty tissue.  Within that tissue, a network of lobes (small tube-like structures) contain the glands where milk is produced.  Tiny ducts connect the glands, lobules and lobes, and carry the milk to the nipple.  The breast also contains blood vessels that nourish the cells and lymphatic vessels that drain bodily waste products.  The lymphatic vessels connect to lymph nodes, small, bean-shaped organs that play a crucial role in fighting infection.

Breast cancers usually arise in either the ducts or lobes.  Almost 75% start in the cells lining the milk ducts and are called ductal carcinomas.  Those that begin in the lobules are called lobular carcinomas.

Breast cancers are classified as either invasive or non-invasive.  Invasive cancers, also known as infiltrating, are those that grow into the surrounding healthy tissues.  Most breast cancers are classified as invasive.  Non-invasive (also known as “in situ”) cancers remain within the breast ducts or lobules and do not invade healthy tissues.