Does lymphoma cause an armpit lump?

Lymph nodes in the armpit help filter fluid from the arm, chest and breast area. Lymphoma can make these nodes enlarge as abnormal lymph cells collect there. The swelling may feel firm or rubbery and may be painless. Infection, skin irritation, an inflamed hair follicle, a cyst or another condition can also enlarge a node. Its location alone cannot identify the cause.

A clinician may ask when you first noticed it, whether it is changing, and whether you have fever, drenching night sweats, persistent fatigue or unexplained weight change. Examination may include checking lymph nodes in other areas and looking at nearby skin or breast tissue. Further tests are chosen from those findings.

Arrange a medical appointment if the lump does not settle, grows, feels hard or fixed, or keeps returning. Note its approximate size, tenderness, movement and any recent infection, vaccination, shaving irritation or injury on that side. Avoid repeatedly pressing it, which can make the area sore.

Bring a list of medicines and relevant symptoms. Assessment may involve an examination, blood tests or imaging; a biopsy is considered when tissue is needed to identify the cells. Only the evaluation can distinguish lymphoma from other causes.

Seek urgent help for trouble breathing, sudden severe swelling, fainting, confusion or feeling acutely unwell with fever. Contact a clinician promptly if an armpit lump is accompanied by persistent fever, drenching night sweats, marked fatigue or unexplained weight change. These features need assessment but do not establish a diagnosis.

What could explain this lump and what features are you checking? Which examination or test is appropriate first? How soon should I return if it changes? Would a biopsy be needed, and what would it show?