Discovering a bump on your shoulder can lead to questions about its origin and significance. Many people encounter these formations, which vary widely in appearance and underlying cause. While some bumps are harmless and resolve on their own, others might indicate a condition requiring attention. Understanding the common types of shoulder bumps can help in discerning when to seek medical advice for further evaluation.
Common Skin-Related Bumps
Bumps on the shoulder often stem from skin conditions affecting hair follicles and skin cells. One frequent cause is acne, which results from hair follicles becoming blocked with excess oil (sebum), dead skin cells, and bacteria [2, 5]. This can manifest as whiteheads and blackheads, or as inflamed red papules, pustules, nodules, and even cysts [2, 14]. External factors like pressure, heat, and friction from tight clothing or backpacks can also trigger a type of acne called acne mechanica [2, 4].
Folliculitis is another common skin-related bump, an inflammation or infection of hair follicles that often resembles acne [7, 16]. It typically presents as small red bumps, sometimes with white or pus-filled centers, and can be itchy or tender [7, 10]. This condition can arise from bacterial infections or from activities like shaving, hot tub use, or excessive sweating, especially when wearing tight clothing that traps moisture [10, 20].
Keratosis pilaris (KP), often referred to as “chicken skin,” creates tiny, rough bumps that are not a form of acne but result from keratin buildup [2, 29]. Keratin can accumulate and block hair follicle openings, forming small, scaly plugs [15, 33]. These bumps typically appear on the upper arms and can be skin-colored, red, or darker on different skin tones [15, 18]. The condition is common and is thought to have a genetic component [18, 21].
Lumps Beneath the Skin’s Surface
Other types of lumps can form beneath the shoulder’s surface, originating from deeper tissues. A lipoma is a common example, characterized as a slow-growing, fatty lump located between the skin and muscle layer [9]. These are typically soft, doughy, movable under the skin, and often less than 2 inches in diameter, though they can grow larger [1, 8]. Lipomas are generally harmless and usually painless unless they press on nerves or contain blood vessels [1, 9]. They commonly appear on the shoulders, back, and arms [1, 8].
Cysts are closed sacs found beneath the skin, filled with fluid, air, or other material [3]. Epidermoid cysts, one of the most common types, are benign and typically contain keratin [3, 23, 24]. These cysts usually form when skin cells move beneath the surface instead of shedding, continuing to multiply and create a sac [23]. They can range in size from millimeters to several inches, and while often painless, they may become inflamed, red, or tender if infected or irritated [23, 24]. Epidermoid cysts are frequently found in areas with more hair, including the upper back and shoulders [23].
When to Consult a Professional
While many shoulder bumps are benign, certain characteristics warrant a medical evaluation. Consult a healthcare professional for any new lump that appears [11]. Specific signs that suggest a need for prompt medical attention include a lump that is growing rapidly, changes in size, shape, or color, or if it becomes painful, red, or warm to the touch [3, 11, 12]. A bump that feels hard, fixed, or does not move easily when touched should also be evaluated [3, 11].
Other indicators for seeking professional advice include any lump that persists for more than two weeks, causes discomfort, or if there are visible changes in the skin overlying the lump [3, 6, 13]. If a bump reappears after being previously removed, or if it is larger than five centimeters (approximately the size of a golf ball), seek medical consultation [3, 25]. These signs can help determine if the bump is a minor skin condition or if it requires further diagnosis and potential treatment. [28]