The term “skin barnacles” is a common, non-medical description for Seborrheic Keratoses (SKs). These non-cancerous growths are the most common benign skin tumors, affecting a large portion of the adult population, particularly as they age. Seborrheic keratoses originate from the outer layer of the skin and do not affect underlying tissues. They are not contagious and pose no risk of becoming skin cancer.
Identifying Seborrheic Keratoses
Seborrheic keratoses have a distinctive appearance, often described as having a “stuck-on” look, as if pressed onto the skin’s surface. They vary in color, ranging from light tan or yellow to dark brown or black. The surface texture is typically dull, waxy, or rough, sometimes appearing warty or scaly. Lesions can be flat initially but usually become slightly raised, forming a round or oval bump. They are most commonly found on the trunk, face, neck, and scalp, and can occur singly or in clusters.
Factors Contributing to Development
The precise cause of seborrheic keratoses is unknown, but several factors contribute to their development. The strongest correlation is with age; most individuals begin developing them after age 40, and they become increasingly common with each decade. Genetic predisposition plays a role, as the growths often run in families. Scientists have identified activating mutations in genes, such as FGFR3, that are frequently present in SK lesions. Sun exposure and hormonal changes, such as those occurring during pregnancy, may also influence their formation.
Distinguishing Them From Serious Conditions
Although seborrheic keratoses are benign, their appearance can sometimes mimic more serious skin conditions, including melanoma. Professional evaluation is necessary to rule out malignancy, as SKs do not transform into cancer. Melanoma typically appears integrated into the skin, while the SK maintains its distinctive “stuck-on” look.
Dermatologists use specific criteria to differentiate a benign SK from a dangerous lesion. Warning signs that warrant immediate attention include a growth that changes rapidly, bleeds spontaneously, or has highly irregular borders. The ABCDE rule for melanoma—Asymmetry, Border irregularity, Color variation, Diameter greater than 6mm, and Evolution (change)—provides a framework for assessing suspicious spots. If a visual examination is inconclusive, a dermatologist may use a dermatoscope or perform a biopsy to confirm the diagnosis.
Options for Removal
Removal of a seborrheic keratosis is not medically necessary since the growths are harmless. Patients usually seek removal for cosmetic reasons or if the lesion becomes irritated, itchy, or catches on clothing. Dermatologists perform several effective, in-office procedures to remove SKs:
- Cryotherapy, which involves applying liquid nitrogen to freeze and destroy the cells, causing the lesion to blister and fall off.
- Curettage, where the physician numbs the area and uses a surgical instrument to gently scrape the growth from the skin’s surface.
- Electrocautery, which uses an electric current to burn and destroy the growth, often combined with curettage for thicker lesions.
- Ablative laser therapy, which vaporizes the growth with a high-energy light source.
Temporary side effects of these procedures can include redness, swelling, or a localized lightening of the treated area.