Sentinel lymph node

October 26, 2023

Lymph nodes are small immune organs located throughout the body. Cancerous tumour cells that escape a tumour often travel to lymph nodes before spreading to other parts of the body. A sentinel lymph node is defined as one of the first lymph nodes a tumour cell will travel to after it leaves the primary tumour.

Patients diagnosed with breast cancer such as invasive ductal carcinoma or skin melanoma of the skin may undergo a procedure called a sentinel lymph node biopsy to look for tumour cells in these lymph nodes. In order to find the sentinel lymph nodes, a doctor will inject a dye or radioactive tracer close to the primary tumour. The doctor will then examine nearby lymph nodes for the colourful dye or use a special machine to find the radioactive tracer. Once found the lymph nodes will be removed and sent to a pathologist for examination under a microscope.

For some types of cancer, pathologists perform a special test called immunohistochemistry (IHC) to look for small groups of tumour cells in sentinel lymph nodes. The chance of finding tumour cells in other lymph nodes is lower and patients have a better prognosis if no tumour cells are found in any of the sentinel lymph nodes examined. Pathologists will describe a lymph node as ‘negative’ if no tumour cells are found and ‘positive’ if tumour cells are found in the lymph node.

About this article

This article was written by doctors to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

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