What should you know about black lump under armpit?

Dark colour may come from a blocked or inflamed hair follicle, a blood-filled blister, a cyst opening, or pigment within a skin growth. A deeper lump may be a swollen lymph node with unrelated darkened skin over it. Appearance alone cannot establish the cause.

Tenderness, warmth, redness, or drainage can accompany an inflamed follicle, boil, or cyst. A smooth lump that shifts under the fingers may arise in the skin or fatty tissue. Lymph nodes sit deeper in the armpit and can enlarge during infection or inflammation.

Breast cancer can present with an armpit lump when nearby lymph nodes are involved, and lymphoma can present with enlarged lymph nodes. Those possibilities do not mean that a dark armpit lump is cancer; an examination is needed to distinguish skin changes from deeper swelling.

Do not squeeze, pierce, or cut the lump. Avoid shaving and fragranced deodorant over sore or broken skin. Note when it appeared, whether it has grown, and whether pain, discharge, fever, breast changes, or other swollen areas are present.

Arrange an appointment with a primary-care clinician or dermatologist. The clinician may inspect the skin, examine both armpits and the breasts or chest, and decide whether imaging or sampling is appropriate.

Seek urgent assessment if redness is spreading, pain is severe, pus is draining with fever, or the arm becomes markedly swollen. Prompt medical review is also warranted for a rapidly enlarging lump, unexplained bleeding, skin breakdown, a hard fixed mass, or a new breast or chest-wall change.

Ask whether the lump seems to arise from skin, a cyst, or a lymph node; whether antibiotics or drainage would be suitable; what changes should trigger urgent reassessment; and whether ultrasound, breast imaging, or a biopsy is needed.