Why New Arm Swelling After Breast Cancer Shouldn’t Be Ignored - Even Years Later

Late-Onset Lymphedema After Breast Cancer: Can Arm Swelling Occur 20 Years Later?

Many breast cancer survivors are surprised to learn that arm swelling can develop decades after cancer treatment. While lymphedema is often thought of as an early complication, it can in fact appear many years — even more than 20 years — after surgery, chemotherapy, or radiation therapy.

A Clinical Vignette: Arm Swelling 21 Years After Breast Cancer Treatment

A woman in her early seventies presented with a six-month history of progressive swelling in her left upper arm. She described a sensation of heaviness and tightness that worsened toward the end of the day. Importantly, she had been treated for left-sided breast cancer 21 years earlier, which included surgery, chemotherapy, and radiation therapy. For more than two decades after treatment, she had remained completely well, with no arm swelling or functional limitation.

Because the swelling persisted and gradually worsened, she sought further evaluation.

Clinical Findings Suggestive of Lymphedema

On physical examination, there was visible swelling of the left upper limb. A Stemmer sign was positive, meaning the skin at the base of the fingers could not be easily pinched. This is a well-recognised clinical sign that strongly suggests lymphedema rather than simple fluid retention or generalized swelling.

However, in patients with a history of cancer, it is essential to exclude other potentially serious and treatable causes before confirming the diagnosis.

Excluding Blood Clots and Central Vein Obstruction

Arm swelling after breast cancer can sometimes be caused by venous thrombosis or central vein narrowing, which can closely mimic lymphedema. For this reason, further imaging was performed.

Ultrasound examination of the deep and superficial veins of the arm showed no evidence of deep vein thrombosis, with normal venous flow extending to the subclavian vein and no collateral veins. A subsequent CT scan of the chest confirmed that the brachiocephalic vein and superior vena cava were normal, with no compression, narrowing, or obstruction.

With venous causes excluded and clinical findings consistent, the diagnosis became clear.

Final Diagnosis: Late-Onset Lymphedema

The patient was diagnosed with late-onset lymphedema, occurring more than 20 years after breast cancer treatment. Although unexpected for many patients, this pattern is well recognised in vascular and lymphatic medicine.

Why Can Lymphedema Appear So Many Years Later?

Breast cancer surgery and radiation can cause permanent damage to the lymphatic system. In many patients, the remaining lymphatic channels are able to compensate for years or even decades. Over time, however, the lymphatic system has a limited reserve.

As a person ages, factors such as gradual tissue scarring from radiation, weight changes, minor infections, or inflammation can overwhelm this reserve. When this happens, lymphedema may finally become clinically apparent, even long after cancer treatment has been completed.

Treatment for Lymphedema After Breast Cancer

Although lymphedema cannot be cured, early and appropriate treatment can significantly improve symptoms and reduce progression. In this case, the patient was referred to a physical therapist with specialised training in lymphatic care.

Treatment focused on manual lymphatic drainage, a gentle and specialised form of massage designed to encourage lymphatic flow. She was also educated on proper skin care to reduce the risk of infection, advised on the appropriate use of compression when needed, and taught long-term self-management strategies. This structured approach is commonly referred to as complete decongestive therapy and remains the cornerstone of lymphedema management worldwide.

A Key Message for Breast Cancer Survivors

Lymphedema has no expiration date. Anyone who has undergone breast cancer surgery or radiation therapy remains at lifelong risk, even if the arm has been completely normal for many years.

Why Accurate Diagnosis Is Important

Not all arm swelling after breast cancer is due to lymphedema. Conditions such as blood clots, venous narrowing, or central vein obstruction can present in a similar way but require very different treatments. A careful clinical examination combined with targeted imaging ensures the correct diagnosis and avoids unnecessary delays in care.

When to Seek Medical Attention

If you have a history of breast cancer treatment and notice new or progressive arm swelling, a sensation of heaviness, or tightening of sleeves, rings, or watches, early medical evaluation is important. Early-stage lymphedema responds best to treatment, and timely intervention can make a meaningful difference in long-term outcomes.