There are specific situations in which mastectomy may be more suitable than breast conserving surgery. It is a difficult choice to make, but you should make the one which best suits your life. There is no difference in the rate of survival or of spread outside the breast and armpit between women having mastectomy and those having breast conserving surgery. Lymph nodes are a common site of spread for cancer. The nodes in the armpit are usually the first place to which a breast cancer spreads outside the breast.
Large cancers are more likely than smaller cancers to spread to the nodes.
Key point Removing the lymph nodes from the armpit does not interfere with the function of your immune system at all. Removing the lymph nodes in the armpit has two main aims. The first is that it helps determine what treatment should follow. The number of lymph nodes affected by cancer gives a very strong indication of the long term effectiveness of treatment. Having no cancer in the lymph nodes is a much better sign than having 10 lymph nodes affected.