Armpit lymph node removal remains standard practice for every patient diagnosed with invasive breast cancer, a procedure that carries the risk of lasting side effects including lymphoedema, pain and reduced mobility.
Current practice
At present, all patients with invasive breast cancer undergo surgery to remove one or more lymph nodes from the armpit — known as the axilla — so that the nodes can be examined for signs of cancer spread. Two main types of procedure are used. Sentinel lymph node biopsy (SLNB) targets only the first lymph node or nodes that drain the tumour. This less invasive approach has significantly reduced the rate of full axillary clearance and its physical side effects, leading to improved quality of life for patients. However, SLNB can still cause lymphoedema in some cases. The more extensive axillary lymph node dissection (ALND) involves removing a larger number of nodes and is associated with higher rates of lymphoedema, pain, reduced strength and limited range of motion.
Lymphoedema, a long-term side effect of lymph node removal or radiotherapy, occurs when fluid builds up, often in the arm or leg. It can be painful, affect mobility and damage self-esteem.
The role of lymph nodes
Lymph nodes are a crucial part of the immune system. They help the body fight infections and cancer by filtering lymphatic fluid and hosting immune cells that detect and respond to threats. In breast cancer, the lymph nodes in the armpit are often the first place the disease spreads to outside the breast itself.
Why armpit lymph nodes are first affected
Breast tissue drains lymphatic fluid — a clear fluid that carries waste products and immune cells — into the lymph nodes under the arm. This drainage network means that cancer cells that break away from a primary breast tumour are most likely to travel first to the axillary lymph nodes. Once there, they can establish secondary tumours, a process known as metastasis. The presence of cancer cells in these nodes is one of the most important indicators of prognosis and guides decisions about further treatment such as chemotherapy or radiotherapy.
Remarkably, even before cancer cells are visibly present in a lymph node, the tumour can already be altering the node’s internal environment. This insight comes from a recent discovery by researchers at King’s College London and University College London, who have shown that structural changes within lymph nodes can serve as early indicators of a patient’s outcome.
New insights from lymph node structure
The King’s College London and UCL team focused on the fibroblast reticular cell (FRC) network — a mesh-like structure inside lymph nodes that supports immune function. They found that changes in this network’s architecture can predict breast cancer outcomes long before cancer cells are detectable in the nodes. The alterations vary depending on the tumour subtype. For example, in aggressive triple-negative breast cancer (TNBC), the FRC network becomes denser and more complex. This denser network was linked to improved survival only when chemotherapy was given before surgery. Conversely, in lymph nodes that already contained cancer spread, similar structural changes were associated with worse outcomes — a more disrupted network correlated with higher tumour burden and poorer survival, while organised networks were linked to better results.
These findings suggest that lymph node remodelling can have either beneficial or harmful effects depending on the disease context and the timing of treatment. The researchers believe that analysing the FRC network could lead to new biomarkers for risk stratification, potentially identifying patients at lower risk who can be spared unnecessary surgery and its side effects. It could also guide treatment decisions, helping doctors determine who needs more aggressive therapy and who might avoid it.
Broader research landscape
This work adds to a wider push towards more personalised breast cancer management. Other advances include the use of artificial intelligence in detection. A UK government-funded AI tool named Mia, piloted at NHS Grampian, successfully identified tiny signs of breast cancer missed by human doctors after analysing mammograms of more than 10,000 women. Google AI research, in collaboration with Imperial College London and the NHS, has demonstrated AI’s potential to detect cancers earlier and more accurately, which could reduce screening workloads.
New imaging techniques are also being explored, particularly for women with dense breast tissue, where standard mammography is less effective. These include radar-based systems, molecular breast imaging (MBI), enhanced ultrasound, contrast-enhanced mammography (CEM) and abbreviated magnetic resonance imaging (AB-MRI), all of which have shown potential in detecting cancers missed by conventional screening.
Genomic testing, such as the Prosigna test, is being studied to identify the likelihood of breast cancer recurrence, potentially sparing patients from chemotherapy. Meanwhile, research continues into environmental factors — including endocrine-disrupting chemicals (EDCs) — that may contribute to breast cancer risk. Key UK institutions leading this work include King’s College London, University College London, the Institute of Cancer Research (supported by Breast Cancer Now), the University of Cambridge, the University of Bristol, Newcastle University and the National Physical Laboratory.
Taken together, the discovery of structural changes in lymph node networks represents a significant step toward more precise risk assessment and treatment planning — one day, possibly, sparing thousands of women from the lifelong consequences of unnecessary lymph node surgery.
