WHAT ARE THE STAGES OF BREAST CANCER?

Doctors use a system called staging to describe the extent of a patient's cancer. Unique staging systems are used for different forms of cancer. In breast cancer, doctors use two systems. One is called TMN staging.

T is for a tumor's diameter. T may be followed by a number (from 0 to 4) or letters. The higher the number, the larger the tumor. Letters, if present, indicate other information about the tumor. (An X indicates the tumor can't be studied.)

N is for the number of diseased axillary lymph nodes a patient has. N is followed by a number (from 0 to 3) that indicates how many lymph nodes test positive for cancer. The higher the number, the more lymph nodes involved. (An X indicates the lymph nodes can't be studied.)

M is for metastasis, or how far the cancer has spread to other parts of the body. M is followed by a 0 (no metastasis) or 1 (metastasis to other organs or tissues detected). cM0 (i+) indicates that a small amount of cancer cells are found in the blood or lymph nodes.

Other factors are considered in staging breast cancer, including whether the tumor has estrogen or progesterone receptors, makes high amounts of a protein called HER2, and the appearance (or grade) of the cancer cells.

Doctors also use a numbering system to stage breast cancer, usually with roman numerals, ranging from 0 to IV.

Stage 0 describes non-invasive forms of breast cancer such as DCIS. Stages I, II, III, and IV are invasive forms of breast cancer. Within each stage, there are subcategories (noted by letters, such as IB) that denote factors such as whether or not a tumor appears to be aggressive.

But, in general, the higher the stage number, the more likely that breast cancer has spread to lymph nodes or, in the case of stage IV, to other organs such as the bones, liver, or brain, making it more challenging to treat.