What should you know about a lump on the side of the breast near the armpit?

The lump may be breast tissue, a blocked or irritated skin gland, a muscle-related swelling, or an enlarged lymph node. Nodes can react to infection or inflammation in the arm, breast, chest wall, or nearby skin. A breast lump near the armpit is a common presentation of breast cancer, while lymphoma can involve lymph nodes; neither condition can be diagnosed from location or touch alone.

Note whether it changes with the menstrual cycle, is tender, moves beneath the skin, or is associated with skin dimpling, nipple discharge, nipple inversion, redness, or a change in breast shape. Also mention a recent vaccine, skin infection, injury, or breastfeeding if relevant.

Book a clinical assessment for a new lump, a lump that remains after an apparent infection, or any breast or skin change that concerns you. The clinician may examine both breasts, the armpits, and the chest wall, then arrange breast imaging. A needle sample or biopsy may be advised when imaging needs tissue confirmation.

Do not squeeze the area. Record when it appeared and whether it changes, and take your list of medicines and previous breast findings to the appointment. Ask how the result will be explained and what follow-up is needed.

Seek urgent care for rapidly spreading redness, severe pain with fever, sudden major swelling, or feeling very unwell. Arrange prompt review for a hard or fixed lump, persistent enlargement, skin tethering or dimpling, bloody nipple discharge, or a newly inverted nipple. These signs require assessment but do not prove breast cancer.

Ask whether the lump feels like breast tissue or a lymph node, which imaging is suitable, whether a sample is needed, whether both armpits should be checked, and what change should trigger an earlier review.