A lump in the armpit is often caused by swollen lymph nodes. This can be a response to an infection, inflammation, or, in some cases, more serious conditions like breast cancer. Other causes include cysts, lipomas (fatty lumps), or blocked sweat glands.

The majority of armpit lumps are harmless and related to minor infections. However, if a lump is persistent, growing, or associated with other changes (like breast symptoms or unexplained weight loss), then it’s important to have it checked by a specialist.

While the majority of armpit lumps are harmless, in some cases they can be linked to breast cancer – particularly if cancer cells have spread to nearby lymph nodes. This is why any unexplained or lasting lump should be assessed, especially if you're also experiencing breast changes.

We’ll take a full history, examine the area, and may recommend imaging tests such as an ultrasound or mammogram. We might also refer you for a biopsy to help us confirm a diagnosis.

If you’ve had a lump for more than two weeks, if it gets larger, feels hard or fixed, or if you have additional symptoms like breast changes, fever, or unexplained fatigue, then we would recommend that you see a doctor.