What is the sentinel lymph node?
- The lymphatic network of the breast drains preferentially to the lymph nodes in the axilla (the armpit).
- The sentinel lymph node is the first lymph node that receives direct drainage from the tumour.
- If malignant cells tend to migrate beyond the breast, they will stop first at this first filtering station.
Why did it replace complete axillary clearance?
In the past, the standard treatment involved radical axillary clearance (lymphadenectomy) — removal of 10 to 20 lymph nodes. This extensive operation was frequently associated with long-term adverse effects: lymphoedema of the arm (chronic, painful swelling of the upper limb from blockage of lymphatic circulation), persistent numbness and limited shoulder mobility.
With sentinel lymph node biopsy, the excision is targeted, which reduces the risk of lymphoedema to under 5%, ensuring a quick and painless recovery.
Who is the procedure for?
Sentinel lymph node biopsy is indicated for patients with:
- Early-stage invasive breast cancer, in which clinical examination and pre-operative axillary ultrasound show no lymph nodes suspected of metastasis (clinically negative axilla – cN0)
- In some cases of ductal carcinoma in situ (DCIS)
- Selected cases after neoadjuvant chemotherapy
If the axillary lymph nodes are already clinically involved and confirmed by pre-operative needle biopsy, the surgical approach is adapted in line with international oncology guidelines.
How is the sentinel lymph node identified? (localisation methods)
To locate the correct node exactly during the operation, modern guidance techniques are used (often combined in a dual-detection technique):
Radiotracer
Before the operation (on the day of surgery or the day before), a radioactive tracer (technetium-99m) is injected around the areola or the tumour. In the operating theatre, the surgeon uses a special detection probe (gamma camera) to measure the signal and find the exact spot in the armpit.
Methylene blue or indocyanine green (ICG)
A substance is injected that travels through the lymphatic vessels, staining the sentinel node blue or allowing it to be seen by fluorescence (the ICG technique).
Magnetic nanoparticles (SPIO)
A non-radioactive technique, in which a suspension of iron oxide is injected and detected intra-operatively with a magnetic sensor.
The stages of the procedure: step by step
Preparation and injection of the tracer
The procedure is carried out in the nuclear medicine department or directly on the operating table, depending on the method chosen.
The surgical approach
Through a fine incision of about 2–3 cm, placed discreetly in a natural fold of the armpit (or through the same incision, if applicable).
Identification and excision
The surgeon removes only the sentinel node(s) – usually between 1 and 3 nodes.
Histopathological examination
Frozen-section examination (intra-operative): in certain situations the node can be analysed quickly during the operation. Paraffin histopathological examination (final): the node is cut into micrometre sections and examined thoroughly with standard stains and immunohistochemistry (to identify any micrometastases or isolated tumour cells).
What happens if the node contains tumour cells?
If the histopathological result shows metastases in the sentinel lymph node, it does not automatically mean a second operation to clear the armpit is needed.
Modern medicine is far more conservative and personalised:
- In patients who have breast-conserving surgery followed by radiotherapy and systemic treatment, the presence of 1–2 positive sentinel nodes no longer requires complete axillary clearance. Radiotherapy and systemic therapies effectively control the residual microscopic disease.
- Only in cases with massive nodal invasion or unfavourable biological factors are complete lymphadenectomy or targeted axillary radiotherapy considered.
Possible risks and adverse reactions
The procedure is a safe one, with a low risk profile:
- Temporary staining: If a dye is used, the skin of the breast may take on a slight greenish/bluish tint that disappears within a few weeks, and the urine may be green in the first 24–48 hours (a completely harmless phenomenon).
- Local collection (seroma) or haematoma: A minor collection of lymphatic fluid in the armpit, which reabsorbs by itself or can be simply drained at a check-up.
- Slight numbness: A slight decrease in sensation on the inner side of the arm or in the armpit.
- Risk of lymphoedema: Remains exceptionally low (under 5%).
Post-operative recovery
- The procedure does not prolong the hospital stay.
- Thanks to the small incision, pain is minimal and is easily controlled with common anti-inflammatories.
- Full mobility of the shoulder and arm is preserved; the patient can resume light activities the next day.
Frequently asked questions
Will I be left without immunity in my arm if the sentinel node is removed?
No. There are between 20 and 40 lymph nodes in the armpit. Removing 1–3 nodes does not affect the capacity of the immune system and allows the lymphatic drainage of the arm to continue normally through the remaining pathways.
Is the injected radioactive substance dangerous for me or my family?
No. The radiation dose used is tiny, similar to or even lower than that of a routine X-ray. It is quickly eliminated from the body in the urine and does not require isolation from loved ones.
What happens if the surgeon cannot find the sentinel node?
Failure to identify the sentinel node is rare (under 1–2% in experienced centres). If it cannot be detected, a low axillary dissection (level I) is carried out to ensure correct staging of the disease.
Want to talk about your situation?
Every case is different. At the consultation we go through the options together.
Medically reviewed by Dr. Răzvan Andrei. Last updated: 1 October 2026.