Sentinel lymph nodes are special lymph nodes among the lymph nodes in the drainage area of the breast and are the first lymph nodes through which lymph node metastasis from breast cancer must occur.
Theoretically, the sentinel lymph node should be located in the first station of the axilla, which is the lateral extent of the outer edge of the pectoralis minor muscle. However, some patients have anatomic variation, and clinically detectable lymph nodes may occasionally be found in the second, third, or even interstitial pectoral lymph nodes, and the number of sentinel lymph nodes may range from one to many, with a median of two.
The deeper the location and greater the number of anterior lymph nodes, the more time-consuming the procedure.
The axillary sentinel lymph node biopsy procedure uses tracer and detection techniques to obtain the axillary sentinel lymph nodes for rigorous pathologic examination, with the goal of understanding the presence of cancer metastases in the axillary lymph nodes.
Prior to the use of sentinel lymph node biopsy, standard breast cancer surgery included “axillary lymph node dissection” because the presence of cancer metastases in the axillary lymph nodes could not be determined prior to surgical treatment, and some patients experienced upper extremity lymphedema and abnormal sensory and motor function in the upper extremities after surgery.
In patients with negative axillary lymph nodes, axillary lymph node dissection only serves to confirm the absence of lymph node metastases, at the cost of risk of upper extremity dysfunction.
Axillary sentinel lymph node biopsy is now used to determine axillary lymph node status, allowing breast cancer patients with negative axillary lymph nodes to avoid axillary lymph node dissection. The risk of upper extremity dysfunction is substantially reduced compared with axillary lymph node dissection.
Sentinel lymph node biopsy is the current method of axillary lymph node status as specified in international consensus and guidelines for the management of breast cancer.