A sentinel lymph node biopsy (SLNB) determines if cancer cells have spread from the primary tumor into the lymphatic system. Surgeons identify and remove the “sentinel” nodes, which are the first lymph nodes to receive drainage from the tumor site. Pathologists examine these nodes for cancer cells. A positive result confirms that the cancer has spread beyond the original site, immediately directing subsequent diagnosis and treatment phases.
Interpreting the Positive Result and Staging Implications
A positive SLNB confirms regional metastasis, meaning the cancer has reached the nearest lymph nodes. The amount of cancer found within the sentinel node influences treatment planning. Pathologists distinguish between two main findings: micrometastases and macrometastases. Micrometastases are small deposits measuring between 0.2 millimeters and 2 millimeters. Macrometastases are larger deposits, exceeding 2 millimeters, indicating greater disease spread.
The presence of cancer cells in the sentinel node automatically changes the cancer’s official stage, typically shifting it from Stage I to Stage II or III. Macrometastases carry a higher risk of further spread to other lymph nodes and are a more important staging factor than micrometastases. Patients with only micrometastases often have a better prognosis and lower risk of non-sentinel node involvement. This distinction helps the oncology team determine the intensity and type of follow-up treatment.
Subsequent Surgical Interventions
A positive sentinel node result often leads to discussion about additional surgical intervention to address the remaining lymph nodes, most commonly in the axilla. The traditional follow-up procedure is an Axillary Lymph Node Dissection (ALND). This involves surgically removing most remaining lymph nodes from the armpit area to remove residual disease and gain a complete picture of the cancer’s spread.
However, a full ALND is not always required, especially for specific breast cancer patients in modern oncology. Clinical trials show that for patients with small primary tumors and only one or two positive sentinel nodes, ALND may be safely omitted if they plan to receive whole-breast radiation. In these cases, the risk of surgically induced complications, such as lymphedema, may outweigh the benefit of removing potentially negative nodes. Lymphedema, chronic swelling of the arm due to lymphatic fluid buildup, is a primary concern whose risk must be balanced against the oncological benefit.
Instead of ALND, the medical team may recommend targeted radiation therapy to the affected lymph node basin to sterilize any microscopic disease. The decision to proceed with ALND, targeted radiation, or observation is highly individualized. It depends on factors such as the size of the primary tumor, the number of positive sentinel nodes, the size of the metastasis (micro or macro), and whether the patient is undergoing a mastectomy or a lumpectomy followed by radiation.
Post-Surgical Treatment Planning
A positive sentinel node result is fundamental in planning systemic adjuvant therapy, beyond immediate surgical or radiation decisions. The presence of cancer in the lymph nodes indicates a higher risk of recurrence, either locally or at distant sites. This finding strengthens the recommendation for additional therapies to eliminate any cancer cells that may have escaped the primary area.
These follow-up treatments fall into several categories: radiation therapy, chemotherapy, hormone therapy, and targeted therapy. Radiation therapy is often delivered to the area where the nodes were removed or the primary tumor was located to reduce local recurrence. Chemotherapy is a systemic treatment that uses drugs to kill rapidly dividing cells throughout the body.
The decision to use hormone therapy or targeted therapy is based on specific characteristics of the primary tumor, such as its receptor status. If the cancer cells are hormone-receptor positive, hormone therapy can block the signals that fuel their growth. If the tumor overexpresses certain proteins, targeted drugs may attack those cells. The positive sentinel node result helps the multidisciplinary cancer team determine the most effective combination of treatments to reduce the risk of the cancer returning.