Quick GuideUnderstanding Cancer: Metastasis, Stages of Cancer, and More
How does a tumor spread?
Tumors have only three ways of spreading:
- By local invasion of adjacent tissue;
- Through the blood stream; and
- Through the lymphatic system.
Some tumors spread preferentially by the lymphatic system, meaning that they tend to spread by this method.
How is it determined which is the sentinel node?
Which lymph node is the sentinel node 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) node and identify it. The tracer substance may be blue dye that can be visually tracked or a radioactive substance or colloid that can be detected as with a Geiger counter or both.
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 tumor cells that have journeyed 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. If the sentinel node is normal, it is unnecessary to perform an extensive dissection of the regional lymph-node basin.
Is the use of the sentinel-lymph-node biopsy common?
Medically reviewed by Jay B. Zatzkin, MD; American Board of Internal Medicine with subspecialty in Medical Oncology
"Sentinel lymph node dissection for breast cancer: Indications and outcomes"