Difference Between Sentinel and Axillary Lymph Nodes

The key difference between sentinel and axillary lymph nodes is that sentinel lymph nodes are the first few lymph nodes into which a tumor drains while axillary lymph nodes are the lymph nodes in the human armpit which are responsible for draining lymph from the breasts and surrounding areas.

The lymphatic system is the network of tissues and organs that transport lymph throughout the body. Lymph nodes are small clumps of immune cells that help to fight against illnesses. Axillary lymph nodes are present in the underarm or the axilla. Sentinel lymph nodes are the lymph nodes into which breast cancer is more likely to spread first. Therefore, sentinel node biopsy is used to check the axillary lymph nodes for the spreading of breast cancer.

CONTENTS

1. Overview and Key Difference
2. What are Sentinel Lymph Nodes
3. What are Axillary Lymph Nodes
4. Similarities Between Sentinel and Axillary Lymph Nodes
5. Side by Side Comparison – Sentinel vs Axillary Lymph Nodes in Tabular Form
6. Summary

What are Sentinel Lymph Nodes?

Sentinel lymph nodes are the first few lymph nodes into which a breast cancer drains. Therefore, they are the first place that the cancer is likely to spread. Surgeons use sentinel node biopsy to identify the lymph nodes into which cancer has spread. They use a harmless dye or a weak radioactive solution to visualize.

If the sentinel node biopsy is negative, it is more likely that all upstream nodes are negative. If it is positive, it means, there may be other positive lymph nodes upstream. Hence, sentinel node biopsy is useful in order to determine which lymph nodes should be removed. It reduces the risk of complications associated with surgically removing all potentially cancerous lymph nodes, unlike axillary dissection, which removes more nodes and disrupt more of the normal tissues in the axilla.  Since few nodes are removed in sentinel node biopsy, most people do not get lymphedema. Therefore, surgeons prefer sentinel node biopsy as the first step to check the axillary lymph nodes for breast cancers.

What are Axillary Lymph Nodes?

Axillary lymph nodes are the group of lymph nodes present in the area of the axilla. Basically, they are the lymph nodes found in the underarm. Our body has about 20 – 40 bean-shaped axillary lymph nodes arranged in five groups as subscapular axillary (posterior), apical (medial or subclavicular), pectoral axillary (anterior), brachial (lateral), and central lymph nodes.

Axillary lymph node dissection is a medical procedure for breast cancer detection. If breast cancer starts spreading, it spreads first into lymph nodes in the underarm (axilla). Thus, axillary lymph nodes can be removed and examined in the lab. In axially node biopsy, it is necessary to remove about 10 to 40 lymph nodes from the area of underarm. Here, more lymph nodes are removed than sentinel node biopsy. Therefore, prior to axillary lymph node biopsy, surgeons prefer sentinel node biopsy since it is less invasive than axillary node biopsy.

What are the Similarities Between Sentinel and Axillary Lymph Nodes?

• Sentinel nodes are usually located in the axillary nodes, under the arm.
• Both sentinel and axially nodes biopsies are used for identification of breast cancers and their spread into other areas.

What is the Difference Between Sentinel and Axillary Lymph Nodes?

Sentinel lymph nodes are the first lymph nodes a tumor is likely to spread. On the other hand, axillary lymph nodes are the lymph nodes found under the arm. Thus, this is the key difference between sentinel and axillary lymph nodes.

Moreover, another significant difference between sentinel and axillary lymph nodes is that in sentinel node biopsy, only a few nodes are removed, so people don’t get lymphedema. In contrast, axillary lymph node dissection removes more nodes and disrupts more of the normal tissue in the underarm area. Therefore, it’s more likely to cause lymphedema.

Summary – Sentinel vs Axillary Lymph Nodes

Sentinel lymph nodes are the first lymph nodes a tumor is likely to spread to. They are usually located in the axillary lymph nodes. Axillary lymph nodes are the lymph nodes found under the arm. Sentinel node biopsy is the most common and less invasive medical procedure for identifying breast cancer and its spreading than axillary lymph node dissection. Thus, this summarizes the difference between sentinel and axillary lymph nodes.

Reference:

1. “Sentinel Node Biopsy – Mayo Clinic”. Mayoclinic.Org, 2020, Available here.
2. “Breast Cancer In Lymph Nodes | Lymph Node Surgery For Breast Cancer”. Cancer.Org, 2020, Available here.

Image Courtesy:

1. “Swollen Lymph Nodes” By Scientificanimations.com – (CC BY-SA 4.0) via Commons Wikimedia 
2. “Gray607” By Henry Vandyke Carter – Henry Gray (1918) Anatomy of the Human Body (See “Book” section below)Bartleby.com: Gray’s Anatomy, Plate 607 (Public Domain) via Commons Wikimedia