Armpit lymph node removal is standard for all invasive breast cancer patients. This procedure, carried out to determine whether the disease has spread, is a cornerstone of staging – but it also carries a risk of long-term side effects including lymphoedema, shoulder stiffness and nerve damage. Now, new research from King’s College London and UCL has identified structural changes inside lymph nodes that could predict breast cancer outcomes, raising the possibility that some patients might one day be spared surgery.
Current practice
Every year around 59,000 women are diagnosed with breast cancer in the UK, and roughly 11,200 die from the disease. For anyone diagnosed with invasive breast cancer, the standard next step is surgery to remove lymph nodes from the armpit – known as the axilla – for examination under a microscope. The extent of that surgery depends on what doctors find.
For early breast cancers with no obvious signs of spread on pre-operative scans, surgeons perform a sentinel lymph node biopsy (SLNB). This less invasive procedure removes only the first few lymph nodes – the sentinel nodes – that drain the breast area. If those nodes are cancer-free, further armpit surgery can usually be avoided, reducing the risk of complications. If cancer cells are found, or if SLNB is not performed, a more extensive axillary lymph node dissection (ALND) may be necessary, removing a larger number of nodes.
Both procedures can lead to complications. Lymphoedema – persistent swelling of the arm, hand, breast or chest due to impaired fluid drainage – is a particular risk, especially after ALND. Patients may also experience pain, numbness, tingling, stiffness in the shoulder and arm, reduced mobility, seroma (fluid build-up) and cording (scar tissue that causes tightness and pain). The accuracy of SLNB after neoadjuvant chemotherapy (treatment given before surgery) is still debated, with some studies reporting a notable false negative rate.
Why the armpit lymph nodes matter
Lymph nodes are a vital component of the immune system, helping the body fight infections and cancer. In breast cancer, the axillary lymph nodes are almost always the first place the disease spreads – a fact that explains why they are the focus of surgical staging. The reason lies in the anatomy of the lymphatic system: lymphatic vessels from the breast drain primarily into the nodes under the arm. Cancer cells that detach from the primary tumour can travel along these channels and lodge themselves in the first nodes they encounter.
Researchers have now discovered that the way lymph nodes respond to a tumour may be far more telling than simply whether they contain cancer cells. A study led by King’s College London, in collaboration with UCL and funded by Breast Cancer Now and Cancer Research UK, has identified structural changes in the fibroblast reticular cell (FRC) network inside lymph nodes. These changes can occur even before cancer cells are visibly detectable in the nodes, suggesting that the tumour can influence distant immune structures at an extremely early stage.
The patterns of the FRC network vary depending on the tumour subtype and how it responds to chemotherapy. This means the lymph node environment is not a passive filter but an active participant in the cancer’s progression – and that its architecture may hold clues about the likely course of the disease.
Implications for breast cancer care
The King’s College London team found that in aggressive subtypes such as triple-negative breast cancer, a denser, more complex FRC network was associated with improved survival when chemotherapy was given before surgery. However, similar structural changes in lymph nodes that already contained metastatic disease were linked to poorer outcomes. These contrasting results suggest that the lymph node’s reaction is dependent on both the tumour’s characteristics and the timing of treatment.
If validated in larger clinical trials, this approach could lead to new biomarkers that allow doctors to stratify patients by risk more accurately. In turn, that might spare some women from unnecessary armpit surgery and its associated side effects. Currently, everyone with invasive breast cancer undergoes node removal for examination – a one-size-fits-all policy that the research could help refine.
Beyond the direct impact on lymph node management, the findings are part of a broader revolution in breast cancer diagnosis and treatment. The NHS Breast Screening Programme currently invites women aged 50-70 for mammograms every three years, and research is exploring how to extend that age range and improve screening for women with dense breast tissue, for whom standard mammograms are less effective. Artificial intelligence is being integrated to help radiologists read mammograms, boosting accuracy and reducing unnecessary biopsies. New imaging techniques such as contrast-enhanced mammography and abbreviated MRI are showing promise in detecting cancers missed by standard mammograms, especially in dense breasts. Radar-based systems and innovative ultrasound technology are also being developed as safer, more comfortable alternatives to X-rays, with potential benefits for younger women and those with dense tissue.
Liquid biopsies – blood tests that can detect cancer DNA – are being trialled for early breast cancer detection and introduced alongside mammograms, while multi-cancer early detection blood tests are under review. On the treatment side, new targeted therapies such as ribociclib combined with an aromatase inhibitor have been approved for early-stage hormone receptor-positive, HER2-negative breast cancer to reduce recurrence. Gene tests now help some patients avoid chemotherapy when it is not necessary, and for aggressive inherited breast cancers associated with BRCA1 and BRCA2 mutations, combining chemotherapy with drugs like olaparib has significantly improved survival. Trials are also exploring new hormone therapy combinations, such as megestrol acetate with letrozole, for post-menopausal women.
Key organisations – including Cancer Research UK, Breast Cancer Now, and the National Institute for Health and Care Research – continue to fund and drive these advances. The new understanding of lymph node structure adds a layer of precision that could eventually alter the standard surgical pathway for thousands of patients each year, making treatment less invasive and more personalised without compromising safety.