Keratoacanthoma

What is keratoacanthoma?

Keratoacanthoma is a skin lesion that erupts in sun-damaged skin, rather like a little volcano. It grows for a few months; then it may shrink and resolve by itself. Keratoacanthoma is considered to be a variant of the keratinocyte skin cancer, squamous cell carcinoma (SCC). As it cannot be clinically reliably distinguished from more severe forms of skin cancer, keratoacanthomas are usually treated surgically.

Keratoacanthoma may start at the site of a minor injury to sun-damaged and hair-bearing skin. At first, it may appear as a small pimple or boil and may be squeezed but is found to have a solid core filled with keratin (scale). It then proliferates, and it may be up to 2cm in diameter by the time it is brought to the attention of the doctor.

See more images of keratoacanthoma.

What causes keratoacanthoma?

Keratoacanthoma arises from hair follicle skin cells for unknown reasons.

Some keratoacanthomas appear to be related to infection with human papillomavirus (HPV), the cause of warts, but the majority of keratoacanthomas are not found to be due to HPV.

What is the treatment for keratoacanthoma?

Keratoacanthomas should be treated for several reasons.

• To obtain pathology: keratoacanthoma can be challenging to distinguish from invasive squamous cell carcinoma.
• To be rid of an unsightly, tender or worrisome lesion
• To minimise the scar, which can be more unsightly if the lesion resolves on its own.

Treatment requires the destruction of the lesion. Options include:

• Cryotherapy (used only for small lesions < 0.5 cm)
• Curettage and cautery or another form of electrosurgery
• Excision
• Radiotherapy.

Follow-up for keratoacanthoma

If keratoacanthoma recurs, it should be treated again.

Patients with keratoacanthomas are at risk of further similar lesions and other skin cancers.

Multiple keratoacanthomas

There are some rare conditions in which multiple keratoacanthomas appear. These are:

• Grzybowski eruptive keratoacanthomas
• Muir-Torre syndrome
• Multiple self-healing squamous epitheliomas of Ferguson-Smith
• Keratoacanthoma centrifugum marginatum
• Drug-induced eruptive keratoacanthomas
  • Responsible medications include BRAF inhibitors vemurafenib and dabrafenib, checkpoint inhibitors pembrolizumab and nivolumab, leflunomide, vismodegib, imiquimod.

Treatment requires surgery as well as oral drugs such as acitretin, methotrexate or cyclophosphamide. Drug-induced eruptive keratoacanthomas induced by checkpoint inhibitors have responded to topical steroids and intralesional steroid injections.