Lymph nodes are important glands that make white blood cells to fight infection. They also filter out bacteria and byproducts of infection. Because lymph nodes are susceptible to the spread of cancer, it’s not unusual for some or all of the underarm lymph nodes to be removed during a mastectomy.
When the lymph nodes are removed, swelling of the arm may occur because the normal drainage pattern of the lymph nodes is disturbed. This swelling and collection of fluid (lymphedema) can cause aching, weakness and a feeling of tightness in the affected arm.
Not every breast cancer patient who has lymph nodes removed will experience lymphedema. And the severity of the symptoms and the timing varies. Some develop lymphedema within days of surgery, and it may only last a short period of time. However, the most common type of lymphedema occurs 18-24 months following surgery and causes chronic problems. Some survivors note several inches of difference between their two arms as a result of the swelling.