Many people regularly check their skin for changes that could be cancer. But not all moles, patches, and rashes are cancerous. In this article, we look at the differences between seborrheic keratosis and skin cancer.

Seborrheic keratosis is a noncancerous condition that can look a lot like melanoma. About 83 million Americans have seborrheic keratosis.

About 5 percent of all new cancer cases in the United States are melanoma, a potentially deadly form of skin cancer. With prompt treatment, more than 91 percent of melanoma patients will survive 5 years or more after their first diagnosis.

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Seborrheic keratosis can look like melanoma but are noncancerous skin growths.

Seborrheic keratoses are harmless skin growths that often appear as the skin ages. Some people have just one, but it is common to develop several. Seborrheic keratosis is not a risk factor for skin cancer or a form of precancer.

Seborrheic keratoses are often brown and patchy and can appear anywhere on the body. The growths may look waxy as if they are painted onto the body. Some people initially mistake them for unusual-looking scabs.

Seborrheic keratoses do not typically cause symptoms, but some people dislike the way they look.

Occasionally, they become inflamed or irritated, causing pain and itching. An injury to a seborrheic keratosis can cause an infection.

Melanoma is a type of skin cancer that can begin as a mole or wart. It kills more people than any other form of skin cancer and can spread to other areas of the body.

On some people, a melanoma may look like seborrheic keratosis. People with a history of seborrheic keratosis might not notice melanoma in its early stages if they are accustomed to unusual skin growths.

Melanoma and seborrheic keratoses are not easy to distinguish, but a dermatologist may be able to tell the difference based on a physical examination. In some cases, however, it is necessary to take a biopsy of the growth to check for cancer under a microscope.

Doctors do not know what causes seborrheic keratosis, or whether it is possible to reduce the risk of developing these skin growths.

The growths are not contagious and do not spread from contact with others. Some people notice that the growths tend to spread on their skin over time.

The primary risk factor appears to be age. Some research suggests that exposure to sunlight may increase the chances of developing seborrheic keratosis.

Other risk factors include:

  • skin irritation and friction, such as along skin folds, particularly in people who already have seborrheic keratosis
  • eczema
  • sunburn
  • viruses, such as human papillomavirus (HPV)
  • genetic mutations
  • a family history of seborrheic keratosis
  • some medications, such as epidermal growth factor receptor inhibitors

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Having fair skin and light hair is a melanoma risk factor.

Over time, ultraviolet (UV) radiation from the sun or tanning beds can change the way the skin behaves. This can lead to cancer, including melanoma.

While sun exposure is one of the most significant risk factors for melanoma, other factors also play a role.

Risk factors for melanoma include:

  • having lots of moles, especially if the moles are unusual
  • having fair skin, light eyes, and light hair
  • a history of melanoma or other skin cancers
  • a weak immune system due to HIV or AIDS, chemotherapy, some medications, and some illnesses
  • a family history of melanoma
  • carrying a genetic mutation that increases the risk of melanoma
  • having moles that are changing

A doctor may be able to distinguish melanoma from seborrheic keratosis with a visual examination. When a doctor is uncertain of the diagnosis, or if a person has a range of risk factors for melanoma, it may be necessary to take a biopsy of the growth.

Seborrheic keratoses are typically:

  • flat
  • waxy
  • painless

Melanoma tends to change and grow over time, so anyone who has a growth that looks like seborrheic keratosis but that changes in shape or color should see a doctor.

People should watch for following signs:

  • Asymmetry: a mole or growth that looks different on one side
  • Border: an irregular border, or a border with jagged edges
  • Color: an uneven or unusual color, or a growth that changes color over time
  • Diameter: changes in size or shape, or larger than a pea
  • Evolving: changing over time

Seborrheic keratoses do not usually cause symptoms and do not necessarily require treatment. However, some people prefer to have them removed because they find the growths unattractive.

If a seborrheic keratosis is damaged or infected, it may need to be removed.

Doctors can remove a seborrheic keratosis using one of a range of minor surgical procedures. The most popular method is to freeze the growth off. A doctor may choose to cut the growth out of the skin or use a process called electrodesiccation, which involves using an electrical current to remove the growth.

Treatment for melanoma depends on a range of factors, including the stage of the cancer and whether it has spread to other areas of the body.

However, treatment almost always requires removing the cancer, as well as any lymph nodes to which it has spread.

Early-stage melanomas may be successfully treated by removal alone. More advanced melanomas sometimes require other treatments, including:

  • chemotherapy
  • radiation
  • immunotherapy, a type of therapy that uses the body’s immune system to fight the cancer
  • targeted drug therapies that treat receptors on tumors

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A doctor or dermatologist should be able to identify seborrheic keratosis from a visual examiniation.

Both seborrheic keratosis and melanoma can appear in many forms. People concerned about skin growths should not try to self-diagnose their condition and should not assume that a new skin growth is benign.

People should see a doctor if they develop any new skin growths, particularly if the growth changes over time or there is a family history of skin cancer.

People with seborrheic keratosis should get regular skin checks. This reduces the likelihood of mistaking melanoma for just another seborrheic keratosis growth. Seeing the doctor annually for a skin and mole check should help reduce the risk of having advanced cancer.