It is now clear for most soft tissue tumors that lymph node removal is not associated with improvement in survival. So why do we still sample, or in some cases even remove, lymph nodes?

Many solid tumors, including breast cancer, skin cancers, thyroid cancer, and even some a sarcomas spread to lymph nodes when they metastasize. Finding tumor cells in lymph nodes means that a tumor is not just invasive with a potential for spread, but actually demonstrates it has the machinery to spread.

In most cases, this elevates the stage of the tumor, and suggests a higher risk for distant recurrence. Tumors with lymph node metastasis are candidates for total body treatment with drug therapy.

The most efficient means of lymph node sampling is through a method called a “sentinel lymph node” biopsy. The sentinel node is the first node, in a bed of lymph nodes, that is likely to receive cells from an upstream tumor. In several tumor types, a negative sentinel lymph node biopsy means that there is a 95% change that any other lymph node removed in that bed would also be negative.

The sentinel lymph node is identified by using a radioactive and a colored due. These are injected near the site of the primary tumor. A special camera may then be used to follow the course of the dye until it collects in the first lymph node it comes to: the sentinel node.

This node may be identified in the operating room with a handheld probe. The probe picks up the low level radioactivity of the protein dye. It should be noted that this radioactivity is of low energy, and quickly dissipates.

An incision can be made over the site of the radioactive hot spot, and the underlying lymph node can be identified using the blue color of the colored dye. This “hot” and blue lymph node is the sentinel node, and can be removed by clipping the lymph channels leading in and out of the lymph node.

Other nodes, and drainage pathways, can be left alone, avoiding the complication of more extensive lymph node procedures, including swelling of the limb and inflammation of the lymph channels.

Sentinel lymph node biopsy is now a standard part of breast cancer and melanoma management. It is frequently used in other high-risk skin cancers, as well.

Although there is no value in prophylactically removing negative draining lymph node beds, there may still be settings in which lymph node beds containing grossly positive nodes may be removed surgically, or treated with radiation therapy, with the goal of controlling local spread of disease.