Subcutaneous masses, or lumps beneath the skin, are common, and the majority are non-cancerous growths that fall into two main categories: cysts or lipomas. Understanding the distinct differences between these common findings is the first step toward seeking appropriate medical guidance. This article provides a fundamental distinction between the two to help readers understand their basic characteristics.
Understanding Cysts
A cyst is a closed sac or capsule that forms beneath the skin, typically lined with epithelial cells. The most frequent type is the epidermoid cyst, which is an encapsulated structure filled with keratin, a protein naturally found in skin and hair. This keratin accumulates inside the sac, leading to the formation of a dome-shaped, slow-growing bump.
These masses are often found on the face, neck, and torso, areas where hair follicles are prevalent. An epidermoid cyst may feel firm or tense to the touch due to the pressure of the trapped cellular material inside. Sometimes, a small, dark opening called a punctum is visible on the skin surface, representing the blocked pore from which the cyst originated.
Understanding Lipomas
A lipoma is a non-cancerous tumor composed entirely of mature fat cells (adipocytes). This growth is an overaccumulation of normal fat tissue encapsulated just below the skin’s surface, usually situated between the skin and the underlying muscle layer. Lipomas represent the most common type of soft tissue tumor found in adults.
When pressed, a lipoma typically feels soft, doughy, or rubbery, mirroring the consistency of the fatty tissue it contains. While they can appear anywhere on the body, they are most often located on the shoulders, back, arms, neck, and upper thighs.
Key Differences in Characteristics
One of the most noticeable differences between the two masses is how they feel upon physical examination. A lipoma is generally highly mobile and can be easily moved or pushed to the side under the skin with light finger pressure, often described as slippery. Cysts, however, are usually more firmly anchored to the superficial layer of the skin, making them less movable and more tethered to the surface.
The texture also provides a distinguishing clue, as lipomas are soft and pliable, whereas cysts are often firmer or feel tense due to the internal pressure of the contents. Lipomas are typically painless, unless the growth expands enough to press upon an adjacent nerve. Conversely, a cyst can become tender or painful, particularly if it ruptures or becomes infected and inflamed.
The internal composition is perhaps the most fundamental difference between the two masses. If a cyst ruptures or is incised, it may release a thick, foul-smelling, cheese-like material, which is the trapped keratin debris. A lipoma, being a solid mass of fat cells, does not drain or release any material.
Treatment and Management Options
The medical approach to managing these two common lumps is based heavily on their composition and behavior. Lipomas are generally left untreated unless they become excessively large, cause chronic pain by compressing surrounding structures, or interfere with movement. If removal is desired, it is typically accomplished through surgical excision, which removes the entire fat mass, or sometimes through liposuction for purely cosmetic purposes.
Cysts are often managed conservatively if they are asymptomatic and small, although they will not resolve completely without intervention. When a cyst becomes infected, inflamed, or is cosmetically bothersome, treatment options include an intralesional steroid injection to reduce inflammation or an incision and drainage procedure.
The most definitive treatment for a cyst requires the complete surgical excision of the entire sac wall, as leaving any portion of the lining can lead to recurrence of the mass. It is important to have any new or changing lump professionally diagnosed to rule out rarer, more serious conditions, even though both cysts and lipomas are almost always benign.