Sentinel Lymph Node Biopsy

Lymph nodes are small, bean-shaped structures that contain cells from the immune system. They filter substances that travel through the lymphatic fluid and are connected to lymph vessels. Lymph nodes can also contain cancer cells that have spread from the site of the cancer into the lymphatic fluid. The sentinel lymph nodes are the first few lymph nodes ("lymph gland") to receive lymphatic drainage from a tumor, meaning that sentinel lymph nodes are the first lymph nodes to which cancer cells would spread. It stands sentinel over the tumor, so to speak. The biopsy is performed to determine if there are cancer cells in the node. If the sentinel lymph node does not contain cancer cells (a negative sentinel lymph node biopsy), then the cancer has not likely spread to lymph nodes or other organs via the lymphatic system.

Sentinel node biopsy is a common technique to assess the extent of spread of breast cancer and can spare the patient more extensive axillary lymph node surgery (see below). It is also frequently used in evaluating patients with melanoma.

Lymphatic system refers to a collection of vessels that, like the system of blood vessels, circulates fluid through the tissues in all parts of the body. The lymphatic drainage refers to the manner in which tissue fluid, or lymph, is drained from the body and returns to a central location -- in this case, a lymph node. The lymphatic fluid has a milky appearance.

Sentinel node ("gland") biopsy is performed to examine the tissue of the node to learn whether that node does or does not have tumor cells within it. The biopsy is performed to verify if there are cancer cells present in the lymph node. This procedure helps the surgeon accurately stage the tumor. Staging a tumor refers to determining the extent to which it has spread in the body. A negative biopsy can avoid the removal of a large number of lymph nodes which can lead to lymphedema. Although lymphedema can be a complication of sentinel lymph node biopsies, it is much more common when multiple lymph nodes need to be removed.

Tumors have only four ways of spreading:

• by local invasion of adjacent tissue,
• by direct growth or extension into nearby tissues,
• through the blood stream, and
• through the lymphatic system.

Some tumors spread preferentially by the lymphatic system, meaning that the cancer cells tend to spread by this method.

Which lymph nodes are the sentinel nodes for a given tumor is determined by injecting around the tumor a tracer substance that will travel through the lymphatic system to the first draining (sentinel) nodes and identify them. The tracer substance may be blue dye that can be visually tracked or a radioactive substance that can be detected as with a hand-held Geiger counter or both.

Sentinel lymph node biopsy is performed by surgeons. This procedure is most commonly performed to evaluate breast cancers and melanomas, so breast surgeons often perform this procedure.

After the tracer substance is injected, the surgeon identifies the sentinel lymph node and surgically removes it through a small incision. This may be done in an outpatient surgery center or a hospital operating room. Sentinel lymph node biopsy is often done at the same time as the removal of a primary tumor.

Biopsy of the sentinel lymph node can reveal whether there are or are not lymphatic metastases, which are cancer cells that have spread from the original primary tumor into the lymphatic drainage system. The sentinel node can be rapidly evaluated while the patient is still in surgery utilizing the technique of frozen section analysis. The final report on the sentinel node awaits the final analysis by the pathologist on what is called formalin fixed tissue.

If the sentinel node contains tumor cells, removal of more nodes in the area may be warranted. This may be done during the same procedure if the first sample is evaluated while the patient is still in the operating room. If the sentinel node is normal, it is unnecessary to remove many additional lymph nodes, such as the axillary lymph nodes (called an axillary lymph node dissection or ALND) in a patient with breast cancer.

The sentinel node biopsy allows the examination of one lymph node to first determine if a tumor has spread to the lymph nodes at all. If the sentinel node is negative for tumor cells, it is not necessary to surgically remove additional lymph nodes. The procedure helps certain patients avoid more extensive surgical procedures involving the removal of multiple lymph nodes, such as axillary lymph node dissection in patients with breast cancer. It means that the patient will not have to experience the side effects of a more extensive lymph node removal procedure, such as lymphedema (swelling) of the arm in patients who have had axillary node dissection. It can be performed in patients undergoing a mastectomy or lumpectomy for breast cancer.

The most common side effects are short-term bruising, pain, or swelling at the biopsy site. As with any surgery, bleeding and infection are possible complications. Another possible risk is a false-negative result, which means that tumor cells are present but not detected by the procedure. Studies with breast cancer patients have shown false-negative rates of around 10%.

Yes. Sentinel lymph node biopsy has, for example, become a standard technique for determining the nodal stage of the disease in some patients with malignant melanoma and with breast cancer. The use of sentinel node biopsy is still being investigated with other types of cancer such as colon cancer, stomach cancers, and others.

The recovery time varies, depending on whether or not the sentinel node biopsy is associated with removal of the primary tumor and the extent of surgery required. In any case, sentinel lymph node biopsy offers a quicker recovery time than a more extensive lymph node dissection.