Sentinel lymph node biopsy is used to diagnose and stage cancer by helping to determine whether the cancer has spread (metastasized). During a sentinel lymph node biopsy, a radioactive substance and/or a dye is injected near the tumor site. The first lymph nodes that absorb the dye are identified as sentinel lymph nodes, because they are the first lymph nodes to which cancer is most likely to spread from a primary tumor.
More than one lymph node may be considered a sentinel lymph node. A sentinel lymph node biopsy involves injecting a radioactive substance, a blue dye or both near the tumor to locate the position of the sentinel lymph node so that it may be removed and tested.
The surgeon removes the sentinel lymph nodes for examination by a pathologist, who tests the tissue for the presence of cancer cells. The biopsy procedure is sometimes referred to as sentinel lymph node dissection because it involves removing just a few lymph nodes for testing. If the sentinel nodes show no signs of cancer, the cancer is less likely to have spread, and the oncologist may recommend that no further lymph nodes be removed. This determination helps inform oncologists in recommending an appropriate treatment plan, while avoiding the unnecessary removal of healthy lymph nodes.
If cancer is found in the sentinel lymph nodes, additional surgery may be needed to remove more lymph nodes. Depending on the circumstances, a sentinel lymph node biopsy may be performed at the same time, before or after the primary tumor is removed.
A sentinel lymph node biopsy is often recommended for breast cancer patients to determine if cancer has spread to the axillary lymph nodes, located under the arm. Sparing healthy lymph nodes in the underarm area may help prevent a condition known as lymphedema, which leads to excess fluid buildup and swelling in the tissue, most often in the extremities, such as the arms and legs.
A sentinel lymph node biopsy may also be an option for melanoma patients whose cancer has a high risk of spreading to the lymph nodes. Sentinel lymph node biopsy also is recommended for some patients to determine if their gynecologic cancer has spread to the pelvic lymph nodes, since it may reduce the risk of complications common to surgeries to remove all the lymph nodes in the pelvic area.