17 Jun 2016

Swellings under the arms - what are they?

Accessory breast tissue is the most common cause of lumps under one or both arms. It is usually soft and frequently tender especially during a woman's period.

The condition is congenital, although it usually only presents after puberty or even later in life. It is common for these lumps to grow as a person gains weight, or as a woman's baseline hormone levels change (usually in her 40s)

Usually this tissue is composed of fat, sometimes breast glands and very occasionally there are extra nipples on the skin surface of the under arm.

The concern for under arm swellings, is whether there are enlarged lymph nodes. Most enlarged lymph nodes represent viral infection and are not dangerous. However, enlarged nodes under the arms can be due to breast cancer that has spread. It would be very unsual for those nodes to be big enough to cause a visible swelling, and they are usually not soft and not tender.

Nonetheless, it's always a good idea to let a doctor have a look at any swellings under your arms, preferably with an ultrasound.


If accessory breast tissue becomes very uncomfortable or unsightly, it can be removed relatively easily - usually by a plastic surgeon.