Keratoacanthoma

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Keratoacanthoma: a simple guide

Keratoacanthoma (KA) is a skin growth that develops quickly over days to weeks. It usually does not spread to other parts of the body and is thought to come from hair follicle cells, but it can look like a skin cancer called squamous cell carcinoma.

What it looks like
- A dome-shaped, smooth, circular lesion with a central crater filled with keratin debris.
- It grows fast and can become large quickly, then may stop growing and heal on its own over months, often leaving a scar.
- Most KA appears on sun-exposed skin such as the face, forearms, and hands. It is rare on mucous membranes.

How it’s diagnosed
- A doctor will examine the lesion and usually need a tissue biopsy to tell KA apart from squamous cell carcinoma.
- In many cases, the whole lesion is removed so the tissue can be checked.

Causes and risk factors
- KA usually occurs in older adults.
- Possible factors include UV exposure, skin injury, immune suppression, and genetics.
- HPV has been studied, but a definite link has not been proven.
- Some cancer drugs, like certain BRAF inhibitors for melanoma, can increase KA risk.

Treatment options
- Surgery: removing the entire lesion with margins (excision) or using Mohs surgery for precise margin control, especially on the face.
- Curettage with electrodessication: scraping the lesion and burning the base, often used on arms, legs, or trunk.
- Cryotherapy (freezing) or radiotherapy in some cases.
- Intralesional chemotherapy (injecting medicines like methotrexate or 5-fluorouracil into the lesion) in selected situations.
- In some cases, if the lesion is unlikely to cause problems and is in a non-cosmetic area, close observation may be considered.

Follow-up and prognosis
- KA is generally low risk for spreading, but about 6% may behave like a cancer and require more aggressive treatment.
- Recurrence can occur and is usually treated promptly with further removal.

Notes
- KA can be difficult to distinguish from skin cancer just by appearance, so biopsy and careful examination are important.