The clavicle, or collarbone, is the long bone connecting the breastbone (sternum) to the shoulder blade (scapula), located just beneath the skin. A lump or swelling in this area, especially near the shoulder, can be concerning due to its superficial position. While many causes are benign, such as injury or soft tissue growths, any new mass requires professional medical evaluation. This area houses important structures, including major blood vessels, nerves, and lymph nodes. Understanding the possible origins provides context, but is not a substitute for a definitive diagnosis.
Causes Stemming from Injury and Bone Healing
A frequent cause of a hard, bony lump on the clavicle is the body’s natural response to a past fracture. When the clavicle breaks, the body creates a bridge of new bone tissue called a fracture callus to stabilize the break during the repair phase. This callus gradually hardens into a firm, palpable lump, often becoming noticeable weeks or months after the initial injury. Although the bone is fully healed, this bony prominence may remain permanently.
A different injury-related lump occurs at the acromioclavicular (AC) joint, where the clavicle meets the shoulder blade. A severe fall directly onto the shoulder can tear the ligaments stabilizing this joint, causing an AC joint separation, or “separated shoulder.” If the stabilizing ligaments are completely torn, the weight of the arm pulls the shoulder blade down, leaving the end of the clavicle sitting high. This misalignment creates a visible, often permanent, step-off deformity or prominent bump on the top of the shoulder.
Lumps Originating in Soft Tissues and Skin
Lumps that feel soft, rubbery, or movable are typically non-bony masses originating from the surrounding fatty tissue or skin layers. A common benign growth is a lipoma, which is a collection of fat cells forming a slow-growing, movable lump just beneath the skin. These growths are usually painless and feel soft or doughy to the touch.
Another category of soft tissue swelling includes cysts, which are enclosed sacs filled with fluid or other substances. A sebaceous cyst is a superficial lump that forms when a hair follicle or skin gland becomes blocked, leading to a buildup of keratin protein. These cysts are generally found right under the skin and may become inflamed or tender if infected. Less frequently, a ganglion cyst, a fluid-filled sac, can arise near joints or tendon sheaths near the clavicle. These cysts are filled with a thick, jelly-like fluid and are typically smooth and firm.
Swelling Associated with Clavicle Joints
Beyond acute injuries, the joints connected to the clavicle can develop chronic issues resulting in swelling and prominence. The AC joint, a frequent site of injury, can be affected by chronic wear and tear, leading to acromioclavicular joint arthritis. This degenerative condition is often seen in people who perform repetitive overhead activities or heavy lifting. The condition causes the joint to swell, enlarge, and become painful, especially with activity.
At the opposite end of the bone, the sternoclavicular (SC) joint, where the clavicle meets the breastbone, can also be a source of swelling. Issues here include arthritis or an inflammatory condition known as Tietze syndrome. Tietze syndrome is a rare, non-infectious inflammation of the costal cartilage that sometimes affects the SC joint. This condition causes localized, painful, and tender swelling, typically located closer to the center of the chest rather than near the shoulder.
Serious Conditions and When to Seek Medical Attention
While the majority of clavicle lumps are benign, some masses signal serious, systemic problems requiring urgent investigation. Enlarged lymph nodes, known as lymphadenopathy, are a primary concern, as the supraclavicular lymph nodes sit just above the collarbone and drain fluid from the chest, abdomen, and pelvis. Swelling in these nodes can indicate infection, systemic illness, or the spread of cancer from a distant site.
An enlarged lymph node on the left side, sometimes called a Virchow’s node, can signal metastatic cancer originating from the abdomen or pelvis. Primary bone tumors, such as Ewing sarcoma or osteosarcoma, are rare but serious causes of clavicle lumps, often presenting as a hard mass. Metastatic tumors are the most common malignant lesions found in the clavicle. Certain “red flag” symptoms should prompt immediate consultation with a healthcare professional to rule out serious conditions.
Red Flag Symptoms
- A lump that is rapidly growing.
- A lump that feels hard and fixed to the underlying tissue.
- Systemic symptoms such as unexplained weight loss, night sweats, or fever.
A medical professional will perform a thorough examination, order necessary imaging like X-rays or an MRI, and potentially perform a biopsy to determine the definitive cause of the lump.