The term "breast cancer" actually describes a variety of cancers that occur within the breast. The different breast cancer types are generally categorized by two factors - where the cancerous cells are located and whether the cancer is prone to spreading.

Breast cancer that occurs in the milk ducts of the breast is called ductal carcinoma [DUK-tal kar-sin-OE-ma]. The breast cancer that forms in the lobules where breast milk is made is called lobular carcinoma [LOB-u-lar kar-sin-OE-ma].

Carcinomas that do not spread outside of the duct or lobule are called in situ [in SY-too] cancers, which mean "in place." If ductal or lobular carcinoma spreads into nearby tissue, it is said to be invasive, or infiltrating. Understanding breast cancer types, size and spread will help you and your doctor select a breast cancer treatment option that is appropriate for you.