Keratoacanthoma: Symptoms, Causes, and UK Management Guide

Keratoacanthoma (KA) is a relatively common skin lesion that is known for its rapid growth. It usually appears as a firm, dome-shaped nodule with a central crater filled with a plug of keratin (a protein found in the skin). In the UK, these are frequently referred to as 'volcano-like' bumps due to their distinct shape. They typically develop on sun-damaged skin in individuals over the age of 50.

Although keratoacanthomas often reach their full size within a few weeks and may eventually resolve on their own, they are clinically significant because they closely resemble a type of skin cancer called squamous cell carcinoma (SCC). Because it is difficult even for specialists to distinguish between the two without a biopsy, NHS guidelines recommend that all suspected keratoacanthomas be treated as if they are potentially malignant until proven otherwise.

Identifying a keratoacanthoma early can help prevent scarring and ensure prompt treatment. The most common characteristics include:

• Rapid growth: The lesion can grow from a small spot to 1–2cm in size within just a few weeks.
• Shape: A raised, symmetrical dome with a central 'plug' of crusty, scaly material.
• Location: Most commonly found on the face, forearms, ears, and the backs of the hands.
• Sensitivity: While usually painless, they can become tender, itchy, or inflamed if caught on clothing.

If you notice a skin growth that is changing rapidly in size or shape, it is important to speak to a professional. You can speak to a GP online to discuss your concerns and determine the next steps for a formal diagnosis.

The exact cause of keratoacanthoma is not fully understood, but several risk factors have been identified by dermatologists in the UK. The most significant factor is long-term exposure to ultraviolet (UV) radiation from the sun or tanning beds. This damage to the skin's DNA causes cells to grow abnormally.

Other potential triggers include:

• Age and skin type: They are more common in fair-skinned individuals and those over 50.
• Chemical exposure: Contact with certain chemicals, such as coal tar or petroleum products.
• Immune system: People with weakened immune systems (immunosuppression) may be more prone to multiple lesions.
• Minor trauma: Some patients report the lesion appearing at the site of a previous scratch or injury.

The Diagnostic Challenge

The primary concern with a keratoacanthoma is its similarity to squamous cell carcinoma (SCC). Under a microscope, the cells of a KA look very much like SCC. NICE (National Institute for Health and Care Excellence) guidance typically advises that because a keratoacanthoma cannot be reliably distinguished from SCC without a full excision, the lesion should be removed surgically.

While a keratoacanthoma might eventually shrink and leave a scar if left alone, an SCC will continue to grow and can potentially spread (metastasise) to other parts of the body. Therefore, UK doctors rarely recommend 'watchful waiting' for these types of growths.

If you have a suspected keratoacanthoma, your GP will likely refer you to a dermatologist or a skin surgery clinic. Common treatments available on the NHS and privately include:

• Excision: The most common method, where the lesion is cut out under local anaesthetic and the wound is closed with stitches. This allows the whole sample to be sent to a lab for testing.
• Curettage and Cautery: The lesion is scraped away with a sharp spoon-like tool (curette), and the base is heat-treated to stop bleeding and destroy remaining cells.
• Cryotherapy: Freezing the lesion with liquid nitrogen, though this is less common for KA as it does not provide a tissue sample for biopsy.
• Topical treatments: In rare cases where surgery isn't possible, creams such as 5-fluorouracil may be used.

If you discover a new or changing lump on your skin, you might feel anxious and want answers quickly. Using a service to speak to a GP online is an excellent first step. An online doctor can review high-quality photographs of the lesion, discuss its growth history, and provide an initial assessment.

While an online GP cannot perform the biopsy itself, they can advise on whether your symptoms match the profile of a keratoacanthoma and provide a referral to a local specialist or private dermatologist. This ensures that you do not ignore a growth that requires urgent investigation, helping you navigate the UK healthcare system efficiently.

To reduce the risk of developing keratoacanthomas and other sun-related skin conditions, follow standard UK health advice for sun safety:

• Use SPF: Apply a broad-spectrum sunscreen (SPF 30 or higher) daily, even on cloudy days.
• Seek Shade: Avoid the sun during the hottest part of the day, usually between 11 am and 3 pm.
• Cover Up: Wear wide-brimmed hats and long sleeves when spending extended periods outdoors.
• Check Regularly: Perform a monthly skin check to look for new spots or changes in existing moles and lesions.