Finding a lump in the armpit (axilla) often causes immediate worry because this area contains a concentrated network of lymph nodes, which are part of the immune system. Most axillary lumps, however, are benign and not related to cancer. This article details the physical characteristics of axillary lumps, explores common non-cancerous causes, and outlines when a lump requires medical evaluation.
Physical Characteristics of Axillary Lumps
When performing a self-examination, the physical characteristics of a lump—how it feels to the touch—offer initial clues about its potential nature. Benign lumps are typically soft, movable, and may cause pain, especially if resulting from infection or inflammation. Benign masses, such as cysts or lipomas, usually move easily under the skin.
In contrast, a lump that is fixed, hard, and painless is concerning. A hard or stony consistency is often associated with malignant growths. A lump that is fixed or tethered to the underlying tissue raises suspicion, as malignant growths can invade surrounding structures.
Lumps that are rapidly growing or those that persist and increase in size over time require medical attention. Lymph nodes that swell due to infection may measure up to two centimeters. Painful lumps frequently result from inflammation or infection, while painlessness is often noted in lumps caused by lymphoma or metastatic cancer.
Common Non-Malignant Causes
The majority of axillary lumps are not cancerous, resulting instead from the body’s defensive or structural functions. The most common cause is lymphadenopathy, or enlarged lymph nodes. Lymph nodes swell when fighting an infection in a nearby area, such as a scratch, a cold, or following a recent vaccination.
These reactive nodes indicate the immune system is producing white blood cells. They are often tender or painful and typically shrink back to normal size within a few weeks after the infection clears. For instance, the COVID-19 vaccine frequently caused temporary lymph node swelling as part of the normal immune response.
Other benign lumps include lipomas, which are soft, doughy, and movable tumors composed of fatty tissue. Cysts, such as epidermoid or sebaceous cysts, are mobile, fluid-filled sacs that feel smooth and rounded.
Hidradenitis suppurativa is a chronic inflammatory skin condition causing painful, deep-seated nodules and abscesses in the armpit due to inflamed hair follicles. Allergic reactions to hygiene products, like antiperspirants, can also trigger a temporary inflammatory response leading to a lump.
Malignant Conditions Involving the Axilla
The axilla is involved in two main types of cancer presentation: metastatic spread and cancer that originates locally. Axillary lymph nodes are the primary drainage pathway for breast tissue. If breast cancer cells spread, the armpit nodes are one of the most common first sites of metastasis.
When cancer cells become trapped, the nodes swell and form a palpable mass. The presence of enlarged axillary lymph nodes is an important factor in breast cancer staging and treatment planning. These metastatic lumps are often hard and fixed to the surrounding tissue.
Lymphoma is a cancer that originates directly in the lymph nodes. This malignancy involves the abnormal growth and multiplication of infection-fighting white blood cells within the node itself. Lymphoma, including Hodgkin’s and non-Hodgkin’s types, frequently presents as a painless lump in the armpit, neck, or groin. Less common malignancies, such as leukemia, melanoma, or squamous cell cancer, can also cause axillary lymph node swelling.
Urgent Symptoms and Next Steps
Any new or persistent lump in the armpit should be evaluated by a healthcare professional. If a lump lasts longer than two weeks, continues to grow, or feels hard and fixed, prompt evaluation is necessary.
Systemic symptoms accompanying the lump also signal the need for urgent medical attention. These “red flags” include:
- Unexplained weight loss
- Persistent fever
- Night sweats
- Changes in the overlying skin
Consult a doctor immediately if the lump is accompanied by swelling of the arm or hand, or changes in the breast tissue. A primary care physician will perform a physical examination, review your medical history, and consider recent infections or vaccinations. They may then order diagnostic tests, such as an ultrasound or a mammogram, to determine the next course of action.