A sebaceous cyst, or atheroma, is a closed sac beneath the skin filled with sebaceous (oily) material. It’s a benign formation resulting from a blockage of the sebaceous glands. Treatment is only necessary if there’s a risk of complications (e.g., mechanical injury or infection).

Sebaceous glands are exocrine glands. When their ducts get blocked, they can’t release their contents, leading to an accumulation of sebum within and around the gland. Besides sebum, cysts contain keratin and cells from the outer hair sheath. During the formation of a sebaceous cyst, or atheroma, a capsule develops around it, restricting it. When the volume of the cyst increases, it appears as whitish bumps on the skin.

How Does a Sebaceous Cyst or Atheroma Look?

The first noticeable sign is a usually painless, whitish nodule or bump beneath or on the skin, which can grow over time. The growth feels elastic to the touch and can be moved slightly under the skin.

The skin above the cyst appears smooth, shiny, and hairless. The cysts can be whitish, flesh-colored, or reddish. Enlarged veins may be visible on the surface. Atheromas commonly appear on the head (including the scalp), back, chest, and genital area, though they can also form on other body parts, except for the palms and soles. The unpleasant odor they emit comes from keratin, a protein produced by sebaceous glands. Nodules may persist for years and grow to the size of a pea, marble, or even an egg.

Causes and Risk Factors for Sebaceous Cysts

Sebaceous cysts form when the duct of a sebaceous gland is blocked or when a swollen hair follicle prevents the gland from draining through the pore.

Sebaceous cysts, or atheromas, typically occur after puberty and are more common in men, with some studies linking them to the male sex hormone testosterone. Women, however, more frequently develop these on the scalp. People who tan extensively or use tanning beds are at higher risk, as are those who had acne during puberty.

Diagnosing Sebaceous Cysts

In most cases, physical examination is sufficient for diagnosis, and a biopsy is rarely needed. Observing and palpating the cyst provides enough information, but it’s necessary to distinguish it from lipomas, fibrolipomas, and neurofibromas.

Infected Sebaceous Cysts: What Happens if an Atheroma is Injured?

Due to their size or location, atheromas can be prone to physical injury, potentially leading to bleeding or infection. The most common complication is an infection, which can lead to an abscess, presenting as redness, pain, and swelling. The skin around the infection site becomes warmer. The cyst’s contents, often foul-smelling, may start to drain. In cases of infection, an incision may be made to drain the purulent material and reduce inflammation. After the inflammation subsides, surgical treatment is advised to prevent recurrence.

How are Atheromas Treated?

Atheromas that don’t cause aesthetic or functional issues usually don’t require treatment.

However, if they cause aesthetic concerns, are in awkward locations, or become infected, treatment is necessary. To resolve the issue permanently and prevent recurrence, the entire cyst and capsule must be removed.

Smaller cysts (7 to 8 millimeters in size) can be removed using radio waves in a single bloodless, scar-free procedure.

Larger cysts require surgical removal under local anesthesia. Techniques used include total excision, minimal excision, and removal through a small puncture.

• Total (or radical) excision: This surgical technique, used if there’s no infection, offers a permanent solution. It involves removing the cyst, its capsule, and some surrounding tissue. The resulting skin defect is stitched up, with stitches removed after 7-14 days. Scar-reducing products are recommended after the procedure.
• Minimal excision: This technique involves removing the cyst in parts through a small incision (about 5 mm). No stitching is needed, leaving a minimal scar.
• Removal through a puncture: This specialized technique is most commonly used for atheromas located on the scalp.

Preventing Sebaceous Cysts

There’s no reliable way to prevent atheromas. People who’ve had atheromas are advised to use oil-free skin products to reduce the likelihood of blocked sebaceous glands, which is a precondition for cyst formation.