How common is an armpit lump in breast cancer?

An armpit lump may be a lymph node reacting to infection, a skin cyst, an inflamed hair follicle, a benign fatty lump or a change related to vaccination. A breast or chest-wall change may occur at the same time, but it may not. A clinician may feel the lump and examine the breast, chest and nearby skin.

Make an appointment for a new lump that persists, grows, feels hard or is fixed, or comes with a breast or nipple change. Note its location, tenderness, size changes and when it appeared. The assessment may involve imaging and, when needed, a sample of tissue or fluid to clarify the cause.

Seek prompt medical advice if the lump is rapidly enlarging, the skin is red and hot, you have fever, or the arm becomes swollen. Ask for urgent guidance for severe pain or feeling acutely unwell. Do not squeeze or repeatedly press the lump.

Ask what features make the lump more or less concerning, whether breast imaging is needed, and when you should expect results. You can also ask what changes in the breast, nipple or arm should lead you to return sooner.