The clavicle, or collarbone, is a long bone connecting the arm to the trunk, running horizontally between the sternum and the shoulder blade. Because it lies just beneath the skin, any change in its structure or surrounding soft tissue is easily noticed as a lump or bump. Finding an unexplained mass can cause worry, making a professional medical evaluation necessary for an accurate diagnosis. This information explores potential causes but is not a substitute for clinical assessment.
Lumps Caused by Injury and Bone Structure Changes
A hard, fixed lump on or near the collarbone frequently results from past trauma or degenerative changes affecting the bone and its joints. The most common cause is a previously sustained clavicle fracture, often resulting from a fall onto the shoulder or an outstretched arm. When the bone heals, the body produces an excess amount of bone material called a callus, which remains as a noticeable, firm bump long after the initial injury has resolved.
Another source of a hard lump is a problem with the acromioclavicular (AC) joint, where the collarbone meets the shoulder blade. A separation of this joint, often called a shoulder separation, can cause the end of the clavicle to push upward, creating a distinct, tender lump near the shoulder tip. Osteoarthritis, a common form of wear-and-tear arthritis, can also lead to bone spurs and inflammation in the AC joint, presenting as a firm enlargement. These bone-related lumps are typically immovable and feel solid.
Soft Tissue Masses: Infection, Inflammation, and Benign Growths
Lumps that feel softer, more mobile, or are located just above the bone often originate from the surrounding soft tissues, including fat, lymph nodes, or fluid-filled sacs. The supraclavicular lymph nodes, situated in the hollow just above the collarbone, are a significant source of soft tissue lumps. Their enlargement, known as lymphadenopathy, usually indicates a response to infection or inflammation elsewhere in the body (e.g., chest, neck, or arm).
When infection causes the lump, the lymph node or abscess will feel painful, tender, and sometimes warm, and the swelling subsides as the infection clears. Persistent or firm supraclavicular lymphadenopathy is a red flag because these nodes drain large areas of the body and can be an early sign of a more serious condition, including metastatic cancer. The left supraclavicular node, specifically, has a unique drainage pathway from the abdomen and chest, making its enlargement particularly noteworthy.
Benign growths are a frequent cause of soft, movable lumps, with lipomas being the most common type. A lipoma is a slow-growing tumor composed of mature fat cells, typically feeling soft or doughy and easily moved beneath the skin. Cysts, which are fluid-filled sacs, can also appear near the collarbone and may feel firm or tense, but are generally harmless. These masses grow slowly and rarely cause symptoms unless they press on an adjacent nerve.
Evaluating the Lump: Characteristics and Diagnostic Tools
A physician’s evaluation begins by observing the lump’s physical characteristics, which helps narrow down the possible causes. The texture is a primary clue; a hard, fixed mass suggests a bony origin like a fracture callus or tumor, while a soft, movable mass points toward a lipoma or a swollen lymph node. The presence of pain, warmth, or redness suggests an inflammatory or infectious process, such as an abscess or osteomyelitis.
The doctor assesses the lump’s mobility, noting if it is freely movable under the skin or tethered to deeper structures like muscle or bone. Changes in size over time are also documented, with rapid growth raising more concern than a mass that has remained stable for years. Based on this initial physical exam, various imaging studies are employed to visualize the internal structure of the lump and its relationship to the clavicle.
Diagnostic Tools
Standard X-rays are typically the first step to assess the bone structure, effectively identifying old or new fractures, bone spurs, and structural deformities. To evaluate soft tissue masses, an ultrasound is a highly effective, non-invasive tool that distinguishes between a fluid-filled cyst, a solid mass like a lipoma, or an enlarged lymph node. For more complex cases, such as those involving deeper structures or suspicion of malignancy, a Computed Tomography (CT) scan or Magnetic Resonance Imaging (MRI) provides detailed cross-sectional images. If the nature of the lump remains unclear after imaging, a biopsy—the removal of a small tissue sample for laboratory analysis—is performed to establish a definitive diagnosis.
Critical Signs Requiring Urgent Medical Evaluation
While many collarbone lumps are benign or related to old injuries, certain accompanying signs necessitate immediate medical attention.
- Rapid growth over weeks or months.
- A lump that is hard, fixed, and immovable, especially if unrelated to a known old fracture.
- Systemic symptoms, including unexplained weight loss, persistent fever, or drenching night sweats.
- Pressure symptoms, such as difficulty swallowing or breathing.
- Significant pain that is worse at night.