What are the stages of breast cancer?
Breast cancer stage is a method that we can use to describe how advanced a particular cancer is. The earliest invasive breast cancers are stage I, where the cancer is limited to the breast itself. Stage II is a little bit more advanced. It involves not only the breast, but some of the lymph nodes, primarily in the armpit. Stage III disease refers to larger cancers that are more advanced, but it isn't until stage IV, the most advanced stage, that the tumor spreads into other organs in the body.
Isn't there a stage earlier than stage I?
Actually, the earliest stage is stage 0. Twenty years ago, these noninvasive breast cancers, which are cancers that haven't yet developed the biological ability to spread to other organs, were a rare event. It occurred in approximately 2 percent to 3 percent of the breast cancers detected every year.
Now, 20 percent to 25 percent of the women who develop breast cancer in the United States will have these noninvasive breast cancers. The most common type of noninvasive breast cancer is ductal carcinoma in situ, which we abbreviate as DCIS. Ductal carcinoma in situ means that under the microscope, the duct tissue within the breast itself has the appearance of a breast cancer, but it hasn't spread outside of the ducts, the tubes within the breast. So it is in place, or in situ.
The other noninvasive breast cancer is lobular carcinoma in situ, or LCIS. Sometimes it's called lobular neoplasia. Lobular carcinoma in situ affects an area of the breast within the lobules, but it's the same idea. It's a breast cancer under the microscope, but remains in place within the lobule.
