The first lymph node to which breast cancer cells are likely to spread from a primary malignant tumor, is known as Sentinel Lymph Node(SLN).
SLNB helps determine if cancer has spread beyond the breast and into the lymph nodes, which is crucial for accurate staging and treatment planning. If the sentinel nodes are negative that is if they have no cancer cells, axillary surgery may be avoided otherwise it can cause complications like lymphedema.
Sentinel lymph node (SLN) dissection is mainly used to assess the axillary lymph nodes in women with early-stage breast cancer (T1-T2, N0) with small tumors of <2 cm size in whom the lymph nodes are not palpable by physical examination or identifiable by imaging studies such as by axillary ultrasound. Any suspicious nodes are biopsied by either Fine needle aspiration cytology(FNAC) or core needle biopsy(CNB).
The sentinel node is localised peroperatively by the injection of patent blue dye such as isosulfan blue or methylene blue and radioisotope-labelled albumin in the breast. The recommended site of injection is in the subdermal plexus around the nipple. The marker in the node is detected visually and with a hand-held gamma camera. Peropererative nodal disease diagnosis is achieved using frozen-section analysis, touch imprint cytology (TIC) or by homogenising the node and detection of a gene such as cytokeratin 19 or mammoglobin.
Mammaglobin and cytokeratin 19 are used as a biomarker for breast cancer, particularly in detecting primary or metastatic breast cancer, monitoring lymph nodes, and predicting disease outcome.
The sentinel node biopsy (SLNB) has transformed the surgical management of early breast cancer, and it is now the standard of care.
Two absolute contraindications for a SLNB are patients with inflammatory breast disease and patients with clinically or biopsy proven positive axillary nodes. These patients would require axillary lymph node dissection.
The SLNB is highly accurate but is a small risk of false-negative results, meaning that cancer cells might be present in other lymph nodes that are not identified as sentinel nodes.
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