Lymph Node Involvement

Some breast cancers spread to the lymph nodes under a woman's arm. When the lymph nodes are involved in the cancer, they are called "positive." When lymph nodes are free or "clear" of cancer, they are called "negative." Your doctors will examine samples from your lymph nodes under a microscope to determine whether any cancer cells have spread there.

In large medical studies, there seems to be a connection between the number of lymph nodes involved and how aggressive a cancer's personality will be. Knowing how many of your lymph nodes are affected by cancer will help you and your doctor find the appropriate treatment to fight the cancer. Read more about options for lymph node surgery.

Doctors think in terms of three types of lymph node involvement when they look at an individual node:

Minimal (or microscopic) lymph node involvement: Only a small number of cancer cells can be found in the lymph nodes.
Significant (or macroscopic) involvement: A particular lymph node or group of nodes has become involved with the cancer. These can often felt by hand or seen without a microscope.
Extra-capsular extension: A breast cancer tumor takes over a whole lymph node and spills beyond the wall of the lymph node into the surrounding fat.
In most cases, the more extensive the lymph node involvement, the more aggressive the cancer. But the extent of disease within a particular lymph node is less important than the total number of lymph nodes affected. The more lymph nodes that are involved, the more threatening the cancer may be.

http://www.breastcancer.org/symptoms/diagnosis/lymph_nodes.jsp