What Is Sentinel Node Biopsy, and Can I Avoid Full Armpit Clearance?

A sentinel node biopsy is a short operation that removes and tests the first one to three lymph nodes in the armpit, the nodes that drain the breast and are the likeliest place for cancer cells to land first. To find them, the surgeon injects a tracer near the tumour or around the nipple, such as a radioactive tracer, blue dye or a magnetic agent. If those nodes are clear, a full armpit clearance is usually not needed, and even when one or two carry cancer, many patients can still avoid it. This blog explains how the test works and how the decision is made.

According to Prof. Dr. Sandeep Nayak, Surgical Oncologist in Bengaluru at MACS Clinic, many patients assume breast cancer surgery always means removing all the armpit nodes, and the fear of a swollen arm is what worries them most. Sentinel node biopsy was developed to spare many of them this. The first nodes are tested, and the result guides whether anything more is needed.

• What it is. The sentinel nodes are the “gatekeepers”, the first nodes that fluid from the tumour reaches. If cancer has begun to spread, it shows up there first. The breast cancer treatment page explains where this test fits in the overall plan.
• The tracer. A radioactive tracer, blue dye, a fluorescent dye (indocyanine green) or a magnetic tracer is injected near the tumour or around the nipple. Many surgeons use two together, which lowers the chance of missing a node.
• The operation. A small cut in the armpit, usually 2 to 3 cm, and one to three nodes are removed. It is normally done at the same sitting as the breast surgery, under anaesthesia.
• The result. A pathologist examines the nodes under the microscope. Sometimes a quick result is available during surgery, and the final report follows in a few days.
• Side effects. Blue dye can turn the urine green and the skin around the injection site bluish for a few days, and allergic reactions are rare. Some patients have numbness, tightness or a small fluid collection (seroma) in the armpit.
• Accuracy. There is a small chance, reported at roughly 5 to 10 percent, that the sentinel nodes look clear while cancer sits elsewhere in the armpit.

• Clear nodes. If the sentinel nodes are free of cancer, no further surgery on the armpit is usually needed.
• One or two positive nodes. The ACOSOG Z0011 trial studied early breast cancer (T1 or T2 tumours) treated with lumpectomy and whole-breast radiotherapy. Patients with one or two positive sentinel nodes who skipped clearance did as well as those who had it, with five-year disease-free survival of about 84 percent against 82 percent.
• Fewer complications. In the same trial, wound infection, seroma and numbness affected about 25 percent after sentinel biopsy alone, against 70 percent after clearance. Arm swelling at one year was reported by 2 percent and 13 percent of patients respectively.
• When clearance is still advised. Three or more positive nodes, nodes already proven to contain cancer on a pre-operative needle biopsy, some mastectomy patients who will not receive radiotherapy, and cancer that remains in the nodes after chemotherapy. In some of these cases, radiotherapy to the armpit can replace surgery.
• Sometimes even the biopsy is skipped. The SOUND and INSEMA trials support omitting sentinel node biopsy in carefully selected women with small, low-risk, hormone-positive cancers and a normal armpit ultrasound. It does not apply to everyone.
• A team decision. A tumour board reviews each case. The blog on choosing a cancer hospital explains what a tumour board is and what to ask.

Four things decide it.

The nodes before surgery. An armpit ultrasound, and a needle biopsy of any suspicious node, show whether cancer is already known to be there.

The tumour and the surgery planned. Lumpectomy with radiotherapy is the setting in which Z0011 applies. A mastectomy without radiotherapy may need a different approach.

The number and size of positive nodes. One or two nodes with limited deposits can often be left alone. Three or more, or nodes that have grown through their capsule, more often need further treatment.

Chemotherapy before surgery. If chemotherapy comes first, sentinel biopsy is done afterwards, usually with two tracers and at least three nodes removed. Clearance is advised if cancer is still found. The full range of cancer operations is on the services page, and more topics are on the Dr. Nayak blogs page.

Key Takeaways

• A sentinel node biopsy removes and tests the first one to three armpit nodes to see whether breast cancer has spread.
• Clear nodes usually mean no further armpit surgery.
• With one or two positive nodes, many early breast cancer patients treated with lumpectomy and radiotherapy can avoid full clearance.
• Clearance carries more complications, including a higher risk of arm swelling.
• Whether you can skip it depends on the nodes, the tumour, the surgery planned and any chemotherapy.

References

1. Cleveland Clinic. Sentinel Node Biopsy. https://my.clevelandclinic.org/health/diagnostics/9192-sentinel-node-biopsy Explains what a sentinel node biopsy is, how the tracer is used and what to expect.
2. Journal of Clinical Oncology (2007). Surgical complications associated with sentinel lymph node dissection plus axillary dissection compared with sentinel node dissection alone in ACOSOG Z0011. https://pubmed.ncbi.nlm.nih.gov/17485711/ Compares infection, seroma, numbness and arm swelling with and without clearance.

Disclaimer: This blog is for informational and educational purposes only and is not a substitute for professional medical advice or diagnosis.