Q. What are the different types of breast cancer and how are they treated?

A. Because of the volume of information associated with this question, I think I will have to break it up into two or three postings.

If we start with broad strokes, breast cancer, as we treat it today, has two main categories – invasive cancer, and in-situ cancer. Invasive means it has broken the basement membrane of a woman’s milk ducts, and in-situ means it is still confined to the insides of the milk ducts – technically meaning this cancer is still outside that woman’s body (highly auspicious).

In-situ breast cancer represents about 15 percent of the total and is also called stage-0 breast cancer. There are three grades of stage-0 cancer: low, medium and high, or grade 1 , 2 and 3. A general rule is the lower the grade, the less aggressive it seems to be.

The most common type of invasive breast cancer is invasive ductal carcinoma. It represents about 65 percent of the disease. Invasive lobular is the next most prevalent, and it represents about 10 percent of all breast cancers. Then there are the special forms, which include mucinous, medullary, papillary, and tubular carcinomas. They represent about 9 percent of total cancers, and the remaining 1 percent include the rare forms, such as Paget’s disease of the nipple and inflammatory breast cancer.

Most of the invasive breast cancers, like in-situ cancers, are also graded as 1, 2 or 3. However, the grade of a breast cancer is different than the stage. There are also high risk lesions that are not breast cancer but are important markers. Over the next month or two I will expand on these topics, and the various treatments, so please stay tuned and remember:

Friends don’t let friends skip mammograms.

Michael J. Ulissey, M.D., is a partner at the Breast Diagnostic Centers of Auburn and Federal Way. In addition to taking care of patients locally, he continues to participate in research as an adjunct professor at the University of Texas Health Sciences Center.