What should you know about cancerous lump armpit?

Infections, inflamed hair follicles, cysts and recent vaccination can cause swelling. Cancer is another possibility, particularly when a node contains cells from a nearby tumour or from lymphoma, but the feel of a lump cannot confirm its cause.

Lymph nodes under the arm filter fluid from the arm, chest wall and breast. They may enlarge while the immune system responds to infection or inflammation. Breast cancer can present with enlarged underarm nodes, and lymphoma can present with persistent enlarged nodes in the armpit or elsewhere. Neither diagnosis can be inferred from swelling alone.

A clinician will consider how long the lump has been present, whether it changes, recent illness or vaccination, skin changes and breast symptoms. Examination may be followed by ultrasound. If the appearance remains unexplained or concerning, a needle sample or biopsy can identify whether the tissue is reactive, infected or malignant.

Book a medical appointment for a lump that persists, enlarges, feels hard or fixed, or occurs with a breast change, unexplained fever, drenching night sweats or unintentional weight loss. Mention recent vaccines, cuts or infections affecting the hand or arm, and any personal history of cancer. Avoid repeatedly squeezing the area because this can worsen irritation.

Record where the swelling is and whether it is tender, but do not rely on self-examination to label it cancerous or harmless. If imaging or sampling is advised, ask how the result will be communicated and whether the breast, chest wall or other lymph-node areas also need assessment.

Seek same-day care if the lump becomes rapidly larger, very painful, red or hot, especially with fever or feeling unwell, as an abscess or spreading infection may need treatment. Get emergency help for difficulty breathing, swelling of the face or throat, fainting, or severe weakness. These urgency signs apply because of the symptoms themselves, not because they establish cancer.

Ask whether the swelling appears to be a lymph node or a skin lesion, whether ultrasound is appropriate, and what features would lead to a biopsy. If you have had breast cancer or lymphoma, ask whether the new finding changes your planned surveillance and which member of your existing cancer team should review it.