A painful lump in the armpit, or axilla, often causes concern because this area is a complex junction of muscle, fat, glands, and lymphatic structures. The axilla contains blood vessels, nerves, and numerous lymph nodes that drain fluid from the chest, arm, and breast. A noticeable lump, especially one that is tender or painful, warrants attention to determine its origin. This article provides a general overview of the causes behind a painful axillary lump.
Lymph Node Activity: Immune Response Causes
The most frequent reason for a painful lump in the armpit is axillary lymphadenopathy, the medical term for swollen lymph nodes. These bean-shaped structures are a central part of the immune system, filtering lymph fluid and housing white blood cells. When the body detects a threat, cells within the nodes multiply rapidly, causing them to enlarge and become tender.
This painful swelling is typically a secondary reaction to an issue located elsewhere in the body. Infections in the surrounding drainage area, such as a common cold, the flu, strep throat, or a localized skin infection on the arm or hand, can trigger this response. Certain medical procedures, including recent vaccinations, can also cause temporary, localized lymph node swelling.
Pain associated with lymphadenopathy is often due to the rapid stretching of the node capsule as it fills with immune cells. This type of lump is mobile and often reduces in size as the underlying infection resolves. Autoimmune conditions like lupus or rheumatoid arthritis can also cause chronic lymph node enlargement by triggering widespread inflammation.
Localized Skin and Gland Conditions
Some painful lumps originate directly within the tissues of the armpit, separate from the deeper lymphatic system. The armpit is rich in hair follicles and sweat glands, making it susceptible to various localized skin conditions. Inflammation and pressure buildup in these structures cause the pain.
A common cause is folliculitis, an infection of a hair follicle often resulting from irritation caused by shaving or plucking. If this infection progresses, it can lead to an abscess, a painful, pus-filled lump formed when bacteria infect the tissue. Abscesses are painful because of the internal pressure exerted by the collected fluid and surrounding inflammation.
Cysts also frequently appear, such as epidermoid cysts, which are sacs filled with keratin debris beneath the skin. A cyst can become inflamed or rupture, leading to sudden pain and tenderness. Hidradenitis suppurativa is a chronic inflammatory skin condition that affects the apocrine sweat glands and hair follicles, causing deep, recurrent, painful lumps that can form tunnels under the skin.
When to Seek Medical Attention
While many painful armpit lumps are benign and resolve on their own, certain characteristics warrant prompt medical evaluation. Consult a healthcare provider if a lump persists for more than two weeks without shrinking or improvement. Any lump that grows rapidly in size or changes noticeably in shape or texture should also be examined immediately.
Specific signs that raise concern include a lump that feels hard, fixed, and immovable when pressed. Lumps that are painless are sometimes more concerning than painful ones, as pain often signals a benign inflammatory process. Seek urgent care if the lump is accompanied by systemic symptoms such as unexplained weight loss, persistent fever, or drenching night sweats. For women, any new lump accompanied by changes in breast tissue or nipple discharge requires specialized examination.
Diagnostic Steps and Treatment Overview
When a patient presents with an axillary lump, the diagnostic process begins with a detailed physical examination and a review of the medical history. The doctor will assess the lump’s size, consistency, mobility, and tenderness to gain initial clues about its nature. Information regarding recent infections, travel, or vaccinations is also important for establishing a potential cause.
If the initial evaluation does not point clearly to a benign cause, imaging tests are commonly ordered. An ultrasound is the preferred first step because it can quickly determine if the mass is solid, cystic, or fatty, and assess the internal structure of the lymph nodes. For women over a certain age or when breast pathology is suspected, a diagnostic mammogram may complement the ultrasound to rule out a hidden breast concern.
In cases where imaging suggests malignancy or the diagnosis remains unclear, a biopsy, such as a fine needle aspiration or core needle biopsy, is performed to collect a tissue sample for definitive analysis.
Treatment is determined entirely by the underlying diagnosis. Lumps caused by infections, such as bacterial abscesses or cellulitis, are usually treated with a course of antibiotics. Localized skin issues, like cysts or large abscesses, may require a minor procedure to drain the fluid and relieve the pressure. For non-infectious, reactive lymph node swelling, often the only necessary treatment is observation, supported by self-care measures like warm compresses and over-the-counter anti-inflammatory medications to manage pain while the body resolves the issue naturally.