Axillary Reverse Mapping: ARM
ARM is a specialist technique intended to identify lymph drainage from the arm during underarm surgery.
The key things to know
- ARM maps arm drainage, not breast sentinel drainage.
- Cancer-involved nodes must not be preserved.
- It may reduce risk but cannot guarantee prevention of lymphoedema.
The idea behind ARM
Breast drainage and arm drainage pass through the axilla. During axillary reverse mapping, a tracer placed in the arm helps the surgeon identify channels and nodes associated with arm drainage. Where it is oncologically safe, preserving some of these structures may reduce disruption of lymph flow. This differs from sentinel-node mapping, which identifies drainage from the breast tumour area.
Cancer clearance remains the priority
The drainage systems can overlap, and a node that drains the arm may still contain cancer. A suspicious or involved node cannot be preserved solely because it is marked by ARM. Suitability depends on disease burden, previous treatment, anatomy, and the surgical team's expertise. The operation must not sacrifice necessary cancer treatment in pursuit of lower swelling risk.
What research suggests
Randomised studies have investigated whether ARM-guided preservation reduces lymphoedema compared with standard axillary surgery. Findings are encouraging in selected settings, but techniques, patient selection, and follow-up differ. It is not a guarantee against lymphoedema and is not available in every centre. Ask whether it is an established local practice or offered within a study.
Questions before surgery
Ask what can realistically be preserved, what findings would change the plan, and how the team measures outcomes. ARM is also different from immediate lymphatic reconstruction, which creates a lymphatic-to-vein bypass. Whether or not a specialist prevention technique is used, early recognition of swelling and access to rehabilitation remain important after underarm treatment.
Take these questions to your appointment
- Is ARM suitable and available in my case?
- How will cancer safety be protected if drainage pathways overlap?
Sources & review
This is original educational content based on the sources below, not reproduced textbook material. Website supervisor: Dr. Nizar Ismail. Individual medical review of this article is pending.
- Randomised clinical trial: reverse lymphatic mapping and lymphoedema ↗
- Randomised trial: axillary reverse mapping for arm-node preservation ↗
- ASBrS: Axillary Management Resource Guide (2026) ↗
This information cannot replace diagnosis or a personal treatment plan. Consult your care team about symptoms or decisions about your treatment.
