Online Dermatologist > Melanoma vs Seborrheic keratosis

Key Takeaways

• Differentiation: Crucial to distinguish seborrheic keratosis from melanoma.
• Seborrheic Keratosis: Waxy, stable, benign skin growths.
• Melanoma: Asymmetrical, multi-colored, changes over time, can bleed.
• When to See a Doctor: New, changing, or painful lesions.
• Conclusion: Regular skin checks and professional evaluations are vital.

Importance of Differentiating Skin Lesions

A dark pigmented lesion on the anterior shin, showing irregular shape and multiple colors. This lesion may indicate melanoma, but it could also be a benign abscess or skin infection. An urgent visit to a dermatologist for examination, ideally with dermoscopy, is highly recommended to ensure accurate diagnosis.

Finding a new, dark patch on the skin can understandably cause concern, as some changes may indicate a potential health issue, including skin cancer. Have your ever wondered whether a skin patch due to ageing or is it a cancer? Most of you would say yes.

Skin lesions often have subtle differences from one another, making it common to mix up harmless and harmful ones. Differentiating melanoma, the most serious form of skin cancer, from seborrheic keratosis, a harmless skin growth appearing with age, can sometimes be challenging. However, for treatment purposes, it is crucial to make a quick, accurate diagnosis.

What is Melanoma?

Image showing a changing mole suspected to be melanoma, with an irregular shape and multiple colors. It’s crucial to differentiate such lesions from benign conditions like seborrheic keratosis.

Malignant melanomas develop when melanocytes (cells containing melanin pigment) proliferate uncontrollably. Although initially confined only to superficial layers of skin such as the epidermis and uppermost dermis ( in situ), malignant cells eventually invade more deeply and may metastasise. The incidence of malignant melanoma in the white population in the United Kingdom and United States is doubling every 10 years,^[1] and the overall incidence is expected to increase by more than 50% by 2040.^[2] This shows the importance of not mixing up melanoma with other benign conditions.

What is Seborrheic keratosis?

Seborrheic keratosis on the trunk, displaying a characteristic raised and waxy texture. Although seborrheic keratosis is benign, it can sometimes resemble melanoma

Seborrheic keratosis is a benign (harmless) type of skin lesion, often referred to as the ‘barnacles of aging’ because it appears with age. Seborrheic keratosis is one of the most common skin lesions, affecting 83 million Americans.^[3]

How to recognize melanoma from seborrheic keratosis?

Regular skin self-assessment helps in timely identification. Examine your entire body, including the back, scalp, palms, soles, and between toes.

Symptoms of melanoma:

If you notice any warning signs of melanoma according to the ABCDE rule in a new lesion or one that looks different from others, see a dermatologist.

A = Asymmetry: One half of the lesion differs from the other half with respect to its shape

B =  Border: The spot will have irregular, scalloped, or poorly defined border.

C=  Colour: Presence of varying colours. It includes shades of tan, brown or black, or areas of white, red, or blue.

D = Diameter: Usually greater than 6 mm that is, about the size of a pencil eraser. But be mindful about even lesions smaller than 6 mm with other melanoma features.

E =  Evolving: The spot will look different from the rest, changing in size, shape, or colour.^[4]

In dermatological practice, the above appearance of melanoma is considered as ‘ugly duckling’ sign.

Read more:

• Can you spot the cancerous mole?
• Skin Cancer Quiz: Can you Spot the bad Mole?

Symptoms of seborrheic keratosis:

Unlike a melanoma which appear and progress quickly, single seborrheic keratosis lesion will have a long development period and a minimal progression. These are the useful features of seborrheic keratosis which will guide you to identify it easily.

1. Starts as small, rough bumps, then slowly thickens and develops a warty surface.
2. Has a waxy, stuck-on-the-skin look.
3. Typically brown, but ranges in colour from white to black.
4. Ranges in size from a fraction of an inch to larger than a half-dollar.
5. Forms multiple lesions on the chest, back, stomach, scalp, face, neck, or other parts of the body (but not on the palms and soles).
6. Causes no pain, though some may itch.^[5]

Comparison of symptoms: Seborrheic keratosis vs. melanoma

*Comparison Table: Key Features and Characteristics of Seborrheic Keratosis vs. Melanoma

What increases your risk of getting melanoma or seborrheic keratosis?

While it is quiet clear what causes malignant melanoma, the risk factors for seborrheic keratosis are not completely known yet.

Common risk factors for malignant melanoma:

1. Genetic: Two or more first-degree relatives affected by melanoma, pre-existing melanocytic naevi.
2. Phenotypic: People with white skin, blond or red hair, many freckles, fair skin that tans poorly, Celtic origin.
3. Environmental: Excessive sun exposure.^[1]

Risk factors for seborrheic keratosis:

1. Familial tendency
2. Increasing age
3. Following an inflammatory dermatosis
4. Very rarely, a sudden eruption of hundreds of itchy lesions may be associated with an internal neoplasm.^[1]

No clear evidence suggests sun exposure as a risk factor, and seborrheic keratosis is not contagious.

How doctors confirm melanoma and seborrheic keratosis?

Diagnosing melanoma:

Your healthcare provider will request an excisional biopsy (removing the lesion with 1-3 mm of normal skin) to confirm the clinical diagnosis and stage the disease.

Diagnosing seborrheic keratosis:

Your dermatologist will identify a seborrheic keratosis by just looking at it. If the lesion appear suspicious a biopsy will be needed.

What are the treatment options available?

Treatment for melanoma:

1. When detected in its earliest stages, melanoma is highly treatable.^[4] There are multiple effective treatment modalities available to cure malignant melanoma.
2. Surgical excision- is the most promising method practiced with a minimal delay. Excisional biopsy is recommended over shave and punched biopsies. After performing histological analysis, your doctor will perform a wider excision to remove as much cancer cells as possible.  If melanoma has spread to the lymph nodes, first a sample of the node will be taken using fine needle aspiration technique. According to the reports, doctor will decide on whether to remove the lymph node or not.
3. Adjunctive therapies – If  melanoma has already spread to internal organs, adjuvant therapies may be given following surgery. But most of those immunotherapy agents used as adjuncts are costly.
4. Chemotherapy is a palliative treatment modality for very advanced disease.
5. Even after successful treatment, follow-up care is essential to detect any recurrence.^[1]

Treatment for seborrheic keratosis:

Seborrheic keratosis can often be left alone unless there are cosmetic concerns. Curettage or cryotherapy can remove the lesions. Curettage, done under local anaesthesia, also provides biopsy samples if needed. Cryotherapy involves applying liquid nitrogen to remove the lesions from your skin. It is the most commonly practiced treatment modality.^[3]

What to expect if you get melanoma or seborrheic keratosis?

Prognosis for melanoma:

The prognosis for patients with non-ulcerated, superficial melanomas less than 1 mm in thickness is excellent. However, poor prognosis is seen in very deep-seated tumours, in males more than females, after 50 years of age, and if the tumour is located on the trunk, upper arms, neck, or scalp, shows ulceration, mitosis, or if lymph nodes are involved and biopsy indicates advanced disease.^[1]

Prognosis for seborrheic keratosis:

After removal, seborrheic keratosis does not usually recur, though new lesions can appear elsewhere.

When to see a doctor? Signs you shouldn’t ignore

Preventing skin damage is essential, so avoid excessive sun exposure, use sunscreen recommended by healthcare professionals, and wear protective clothing and hats. Perform regular skin self-examinations, and seek medical advice if you have:

1. New or rapidly changing lesions.
2. Lesions that bleed, itch, or become painful.
3. Any growths that look suspicious or different from others.

Know the differences, protect your skin

Malignant melanoma and seborrheic keratosis, which are malignant and benign skin conditions respectively, can be easily misdiagnosed due to their similar appearances. While melanomas show ‘Ugly duckling’ , seborrheic keratosis will appear as ‘barnacles of aging’.   Knowing when to be alarmed and seek professional help will protect your skin and yourself from unnecessary burden. Since dermatological knowledge and treatment modalities are evolving day by day, staying informed and aware of both diseases and their treatment modalities is worthwhile to ensure timely and appropriate care.