A lump under the skin of the armpit

Its depth, mobility, tenderness, skin appearance, and change over time help guide assessment. These features cannot reliably establish the cause at home, so a persistent or changing lump should be examined.

Lymph nodes can swell in response to infection or inflammation in the arm, breast, or nearby skin. A blocked skin structure may form a smooth cyst, while a painful warm swelling may contain infection. A soft mobile lump can arise from fatty tissue.

Breast cancer can present with an enlarged armpit node or breast and nipple changes. Lymphoma can present with enlarged nodes that may not be tender. Because benign and serious causes can overlap in feel, size or tenderness should not be used alone to label the lump.

Do not squeeze, massage, lance, or repeatedly check the lump. These actions can inflame tissue or spread an infection. Avoid shaving directly over it, keep the skin clean, and use a warm compress for comfort if the area is tender.

Write down when you noticed it and whether it enlarges, becomes fixed, drains, or develops redness. Also note recent skin infections, wounds, vaccinations, illness, and any breast, chest, or arm changes to share during an appointment.

Arrange a medical review if the lump persists, grows, returns, feels hard or fixed, or has no clear link to a temporary skin problem or illness. Assessment is also needed with breast thickening, skin dimpling, nipple inversion, nipple discharge, night sweats, or unexplained weight loss.

Seek urgent care if the lump becomes rapidly larger or very painful, redness spreads, pus drains with worsening symptoms, fever develops, or you feel significantly unwell. A collection of infection may require treatment rather than home drainage.

Ask whether the lump seems connected to the skin, fatty tissue, or a lymph node, and whether nearby areas should be examined. If the cause remains uncertain, ask what imaging or sampling could clarify it and when follow-up should occur if observation is advised.