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Sentinel Lymph Node Biopsy (cont.)

Breast Cancer Diagnosis and Treatment
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How does a tumor spread?

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.

How is it determined which is the sentinel node?

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.

What types of specialists perform a sentinel lymph node biopsy?

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.

What happens during a sentinel lymph node biopsy?

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.

What does the sentinel lymph node biopsy show?

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.

Medically Reviewed by a Doctor on 3/13/2018


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