Seborrheic Keratosis vs. Melanoma: What’s the Difference?

Medically reviewed by Alana Biggers, MD on July 25, 2017Written by Marjorie Hecht on July 25, 2017

Why people confuse the two

Seborrheic keratosis is a common, benign skin condition. These growths are often referred to as moles.

Although seborrheic keratosis typically isn’t cause for concern, its look-alike — melanoma — is. Melanoma is a potentially deadly type of skin cancer.

Malignant growths often take on the same shape and color as harmless moles, so it’s important to understand the difference between the two. Here’s what you need to know.

Tips for identification

Seborrheic keratosis growthsCommon to bothMelanoma growths
are round or oval shaped
can also be light tan in color
have a waxy or scaly surface
may be capped or stick above the surface
often appear in groups of two or more
typically stay the same size
growths can be brown or black
growths can vary in size
growths can appear anywhere on the body
may have sides that don’t match in size or shape
can have a fuzzy border, or ragged or blurred edges
can also have a variety of colors within the same mole
have a smooth surface
may bleed or ooze
may change color, shape, or size over time

Seborrheic keratosis

Seborrheic keratosis becomes more common as you age, and it’s more likely to affect people who have lighter skin tones.

Seborrheic keratosis usually appears on your:

  • face
  • chest
  • shoulders
  • back

Growths commonly:

  • are round or oval shaped
  • vary in size from very small to more than 1 inch across
  • appear in groups of two or more
  • are brown, black, or light tan in color
  • have a waxy or scaly surface
  • are slightly elevated above skin level

Often these growths look as though they’ve been pasted onto your skin. Sometimes they may take on a wart-like appearance. They generally aren’t painful or tender to the touch, unless they’ve become irritated from rubbing or scratching against your clothing.

Melanoma

Melanoma also becomes more common as you age. On men, malignant growths usually appear on the back, head, or neck. On women, they are more common on the arms or legs.

The ABCDE rule can help you distinguish most melanoma growths from benign moles. The five letters of the acronym stand for the features to look for in a melanoma. If you notice any of these, you should see your doctor:

  • Asymmetry: opposite sides of the mole don’t match in size or shape
  • Border: a fuzzy border, or ragged or blurred edges
  • Color: a variety of colors within the same mole
  • Diameter: moles larger than 1/4 inch, or growing over time
  • Evolving: moles that change shape, color, or symptom, including redness, scaling, bleeding, or oozing

Are they caused by the same things?

Seborrheic keratosis

Researchers aren’t sure what causes seborrheic keratosis. It does seem to run in families, so genetics may be involved.

Unlike melanoma, seborrheic keratosis doesn’t relate to sun exposure.

Melanoma

Overexposure to ultraviolet light (UV) from natural sunlight or tanning beds is a major cause of melanoma. The UV rays damage the DNA in your skin cells, leading them to become cancerous. With proper sun protection, this may be preventable.

Heredity also plays a role. You’re twice as likely to develop the disease if a parent or sibling has previously been diagnosed with melanoma.

Still, only about 1 in every 10 people diagnosed with melanoma also have a family member who has the disease. Most melanoma diagnoses relate back to sun exposure.

What’s the process of diagnosis?

Your dermatologist will likely begin by examining the surface characteristics of your growth with a magnifier.

Although there are visual differences between the two conditions, they can be misleading. Melanomas sometimes mimic features of seborrheic keratosis so successfully that misdiagnoses are possible. If there’s any doubt, your dermatologist will take a sample of your mole, known as a biopsy, and submit it to a laboratory for testing.

Newer diagnostic tests, such as reflectance confocal microscopy, don’t require a skin sample. This type of optical biopsy uses a special microscope to perform a noninvasive examination. This exam is widely used in Europe and is becoming available in the United States.

What treatment options are available?

Seborrheic keratosis

Seborrheic keratosis is a benign condition that is usually left alone.

The one exception to this is when multiple seborrheic keratoses appear suddenly. If this happens, it may be a sign of a tumor growing inside your body. Your doctor will test for any underlying conditions and work with you on any next steps.

Melanoma

Although melanoma accounts for about 1 percent of all skin cancers, it’s responsible for the majority of skin cancer-related deaths. If the melanoma is detected early on, surgical removal of the growth may be all that’s needed to remove the cancer from your body.

If the melanoma is discovered in a skin biopsy, you may need a surgical excision around the biopsy site to remove any possible additional cancerous tissue. Your doctor will use local anesthesia to numb the area before cutting into the skin. They’ll cut the tumor out, along with a small margin of healthy tissue surrounding it. This leaves a scar.

About 50 percent of melanomas spread to lymph nodes. Your doctor will biopsy the nearby nodes to determine whether they need to be removed along with the tumor and healthy skin sample. This procedure is known as dissection.

If the melanoma has spread to other organs (metastasized), your treatment will likely focus on symptom management. Surgery and other treatments, such as immunotherapy, may help extend and improve your quality of life. Newer drugs known as immune checkpoint inhibitors show a lot of promise for advanced melanomas. Talk to your doctor about what options may be right for you.

Outlook

Seborrheic keratosis is typically benign, so these growths shouldn’t have any impact on your outlook or quality of life.

If melanoma is diagnosed, your doctor is your best resource for information about your individual outlook.

This can depend on a number of factors, including:

  • whether the cancer has spread
  • how early the cancer was caught
  • whether you’ve had a cancerous growth before

Research is ongoing to find new ways to treat melanoma at all stages. If you’re interested in participating in a clinical trial for a new therapy, talk with your doctor. They can provide you with information about open trials in your area. They can also help you connect with a support group.

Tips for prevention

Both seborrheic keratosis and melanoma have been linked to sun exposure. The best way to reduce your risk for either condition is to stay away from tanning beds and be smart about sun protection.

You should:

  • Apply sunscreen with an SPF of 30 or higher every day.
  • If your skin is very fair or you have a family history of melanoma, use SPF 50 or higher.
  • Reapply your sunscreen every two hours and immediately after sweating heavily or swimming.
  • Avoid being in direct sunlight between 10 a.m. and 4 p.m., which is when the sun’s rays are most penetrating.
  • Watch for changes in any existing moles. If you see anything unusual, schedule an appointment with your doctor.
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