A Guide to Understanding Skin Lumps
Finding a lump beneath the skin can cause concern, but most growths are non-cancerous and common. Cysts and lipomas are frequently encountered benign skin growths that are often mistaken for one another. While both present as masses under the skin, their origins, contents, and physical characteristics differ. Understanding these distinctions is important for proper identification and management.
Composition and Nature
A cyst is a closed sac-like pocket that develops beneath the skin, forming a distinct wall made of epithelial cells. This structure is filled with a substance that can be liquid, semi-solid, or air, depending on the type. The most common type, an epidermoid cyst, is filled with keratin, a protein found in skin and hair, often giving the contents a thick, cheese-like consistency. Cysts typically form when a hair follicle or oil gland duct becomes blocked, trapping skin cells and debris inside the sac.
A lipoma is a benign tumor composed entirely of mature fat cells (adipocytes) that have overgrown. It is a soft tissue growth located in the subcutaneous layer just beneath the skin. Unlike a cyst, a lipoma does not have a fluid-filled cavity or a lining of skin cells; it is simply a collection of fat encapsulated by a thin fibrous layer. The formation of a lipoma is considered a form of benign neoplasm, or new growth, of fat tissue, and is not due to a blockage.
Physical Characteristics and Common Sites
The most noticeable differences between these two growths are their texture and mobility upon physical examination. A lipoma feels soft, doughy, or rubbery to the touch and can be easily moved or “slipped” beneath the skin. These fatty lumps are usually painless, grow very slowly, and maintain a smooth, dome-shaped appearance. Common locations for lipomas include the shoulders, back, neck, arms, and thighs, areas where subcutaneous fat is abundant.
In contrast, a cyst generally feels firmer and more fixed to the overlying skin, making it less mobile when pressed. Some cysts may have a central punctum, appearing as a small dark spot or pore on the skin’s surface, characteristic of epidermoid cysts. Cysts are prone to becoming inflamed, which causes redness, swelling, and tenderness, especially if the internal sac ruptures or becomes infected. Cysts are most often found on the face, neck, and trunk, often near oil glands, but they can occur almost anywhere.
Medical Assessment and Management
A medical professional can differentiate between a cyst and a lipoma through a physical examination, assessing the lump’s texture, mobility, and location. If the diagnosis is unclear, an ultrasound is commonly used, as it easily distinguishes between a solid mass (lipoma) and a fluid-filled structure (cyst). Biopsies are rarely needed unless the lump is growing rapidly, feels unusually hard, or exhibits other concerning features.
For a lipoma, treatment is optional unless the growth is painful, very large, or causing cosmetic distress. The primary method of removal is simple surgical excision; liposuction may be used for larger, softer lipomas to extract the fatty tissue. Cysts are often treated if they become tender, infected, or cause irritation. Management for a cyst involves draining the contents if inflamed, but complete surgical removal of the entire cyst wall is necessary to prevent recurrence. Both growths are benign and do not pose a cancer risk.