An Overview of Seborrheic Keratosis

Seborrheic keratosis is a dermatologic condition characterized by wart-like growths that may appear anywhere on the skin except for the palms and soles. Growths can vary in appearance but are typically:

• Light tan to dark brown
• Round,
• Waxy or warty
• Have a stuck-on-the-skin appearance

While they're harmless, some people seek treatment for aesthetic purposes and because the growths can become irritated or get caught on clothes and jewelry.

Seborrheic keratoses develop in a type of skin cell called a keratinocyte on the outermost layer of skin (epidermis). While most dermatologists can diagnose them by appearance alone, they may perform a skin biopsy to rule out worrisome conditions like skin cancer.

Symptoms of Seborrheic Keratosis

Seborrheic keratosis is a noncancerous skin growth that has the following typical characteristics:

• Rests flat against the skin or is raised
• Starts off as a small, round bump that then thickens and develops a waxy or wart-like appearance (although in some cases, the surface is smooth)
• Usually brown but may also be white, black, yellow, or grey
• Develops anywhere on the skin (e.g., chest, back, face, and neck), but not on the palms and soles
• Appears on its own or within groups
• Ranges in size from a pinpoint to over an inch in diameter

This photo contains content that some people may find graphic or disturbing.

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This photo contains content that some people may find graphic or disturbing.

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Because only the top skin layer is involved, seborrheic keratosis often has a "pasted-on" appearance, similar to a barnacle. The number of growths typically increases as you age.

Seborrheic keratoses are not painful but may itch, especially as you get older. If scratched or picked at, the growths can become irritated.

Presence of Other Symptoms

While seborrheic keratosis is considered a benign skin condition, in rare cases, skin cancer (e.g., squamous cell carcinoma or basal cell carcinoma) can arise from cells that are contained within a seborrheic keratosis.

Research suggests that people with a suppressed immune system may have an increased risk of this phenomenon, which is called a malignant or cancerous transformation of a seborrheic keratosis.

This is why careful observation of these growths by a dermatologist is important, especially if atypical signs are present, such as:

• Ulceration (sores)
• Excoriations (scratch marks)
• Redness
• Bleeding on or around seborrheic keratoses

Causes

The precise cause of seborrheic keratosis remains unknown. Experts believe genes play a role, as these growths tend to run in families. Other factors that may increase your chances of developing them include:

• Sunlight exposure
• Chronic friction (such as inside skin folds)
• Exposure to viruses, specifically the human papillomavirus (HPV), although this theory has lost a lot of favor over the years

Diagnosis

A dermatologist can usually diagnose seborrheic keratosis simply by its outright appearance or by using a lighted instrument called a dermatoscope.

However, in some instances, if the growth looks suspicious for skin cancer or there's any doubt about what they are, a skin biopsy can confirm a diagnosis.

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This photo contains content that some people may find graphic or disturbing.

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The different types of skin biopsies that may be performed include:

• Shave biopsy: The lesion is shaved to remove a tissue sample.
• Punch biopsy: A hole-punch-type device removes a narrow cylinder of tissue.
• Excisional biopsy: The entire lesion is removed with a scalpel.

A pathologist then examines the skin samples under a microscope. If they find cancer cells, you'll need additional testing to determine the stage of the cancer, which will guide treatment.

Treatment

Seborrheic keratosis doesn't typically need treatment unless you consider it cosmetically undesirable, it's uncomfortably itchy, or it's easily irritated.

The good news is that there are several different treatment options available:

• Cryotherapy with liquid nitrogen: The growth is frozen off with liquid nitrogen (an extremely cold liquid)
• Shave excision: It's removed with a sterile razor
• Curettage: It's scooped out with an instrument called a curette
• Electrocautery: The tissue is burned with an electrical current
• Chemical peel: A solution such as trichloroacetic acid causes the growth to slough off
• Ablative laser treatment: A laser removes the layer of skin

Research suggests that laser therapy is a better alternative than cryotherapy, as it's less likely to cause hyperpigmentation (when removal of the growth causes darkening of the skin).

A Word From Verywell

Seborrheic keratosis can sometimes be difficult to distinguish from skin cancer, especially when it first appears. It's important to not make assumptions about any new spots, patches, or growths that develop on your skin. Be proactive and see a dermatologist for a proper diagnosis and treatment plan.