Blue Dye

Each of us has about 50 lymph nodes under each armpit. The purpose of lymph nodes is to filter the lymphatic circulation. If a breast cancer was to spread, it would travel to the sentinel lymph node or "gate keeper node" first before spreading to the other lymph nodes in the armpit. The sentinel lymph node is identified by injecting either one or two dyes into the breast. The most common "dye" is a radiotracer that the nuclear medicine doctor injects into the breast before the surgery. Another dye is a blue dye injected by a surgeon into the breast during the surgery while the patient is asleep. Each dye is picked up by the lymphatic circulation in the breast and travels to the sentinel lymph node making it either radioactive or blue. This is how the surgeon can identify the node and surgically remove it to have the pathologist check it for cancer.

Most surgeons will use a combination of both the radiotracer and blue dye to identify the sentinel lymph node. However, some surgeons will rely on only one type of dye. In my practice, I usually only use the radiotracer since the blue dye can result in a blue stain on the skin and in rare cases an allergic reaction. There is no way to surgically find the sentinel lymph node without the injection of either the radiotracer or blue dye into the breast.