What is a Keratoacanthoma?
A keratoacanthoma is a common skin tumour that is found on sun-damaged skin. It is not malignant and usually grows very slowly over a period of weeks. It begins as a skin lesion that looks like a small pimple, and eventually becomes a rounded mass. It has a central crater that is filled with a hard and scaly core composed of keratin. The tumour may range from 5 mm to 15 mm in diameter.
Normally there is only one lesion, but in rare cases multiple lesions may be seen. This is known as multiple keratoacanthomas. Multiple lesions usually occur in people with Muir-Torre syndrome, Grzybowski eruptive keratoacanthomas, multiple self-healing squamous epitheliomas of Ferguson-Smith, and keratoacanthoma centrifugum marginatum.
The Natural History of Keratoacanthoma
Keratoacanthomas grow on the skin, beginning from a size of 1 to 2 mm. At this time the skin may feel sore and tender. The growth originates in the skin cells surrounding the hair follicle or the pilosebaceous glands. It rapidly increases in size but stops growing in about 6 to 8 weeks. At this time it has a central keratin core. It persists unchanged for a period of 2 to 6 weeks.
Eventually, the lesion starts to regress. Over 2 to 12 months it may begin to flatten and the core falls out. Only a saucer-shaped scar is left. These skin lesions tend to occur due to regular exposure to ultraviolet radiation from the sun. They are most likely to form on areas that are exposed, like the face and hands.
How is it Diagnosed?
Keratoacanthomas are often very similar to squamous cell cancers (SCC). The latter is a much more aggressive tumor, being a cancer of the skin, which needs to be closely monitored. Since there is no way to distinguish between the two on the basis of simple observation, the surgical removal of any tumour which resembles it is recommended. A dermatologist typically performs this minor surgery.
The biopsy allows the health care professional to determine if the skin lesion is a benign keratoacanthoma or a malignant SCC. However, even this may not be conclusive. Therefore it is recommended that the lesion be completely removed as an SCC can easily spread to the lymph nodes if left unchecked, and eventually ravage the person’s body.
Can Keratoacanthomas be Cured?
Should the skin lesion prove to be a keratoacanthoma rather than an SCC, the excision itself will be the cure. As long as the dermatologist performing the surgery does not leave any tumor cells behind, the skin condition will not reappear. The whole lesion is cut out and the skin is sutured together after the process to aid rapid healing. Dressing of the wound may be required for a few days.
Surgery is usually advised for a keratoacanthoma, even though it may spontaneously regress and heal, leaving behind a crater-shaped scar, though the process may take a few months. For those who develop multiple keratoacanthomas an oral retinoid such as Acitretin may be prescribed to reduce the risk of development of new lesions.
There are different techniques to remove a keratoacanthoma. They include:
- Excision: Cutting away the skin lesion physically with a surgical instrument.
- Curettage and cautery: An electrosurgery procedure where the skin lesion is scraped off and heat is applied to the surface of the skin.
- Cryotherapy: Skin lesions are frozen using liquid nitrogen, carbon dioxide snow, or dimethyl ether and propane.
- Radiotherapy: Radiation in small bursts is applied to the targeted cancerous tissue and the energy that is transmitted destroys the cancerous cells.
The exact method used for treatment of keratoacanthoma will differ based on the individual’s condition and the dermatologist’s decision.
Who is More Likely to get Keratoacanthoma?
While keratoacanthoma is not a hereditary illness, people who get multiple skin lesions (which is rare) do have a family history of the disease. In most cases, the illness manifests in light-skinned people who tend to have over-exposure to the sun. It is more likely to strike elderly individuals. Again, there is a tendency for those with weakened immune systems to develop a keratoacanthoma.
Sometimes infection with the Human Papilloma Virus (HPV) may be related to the emergence of Keratoacanthoma lesions. HPV is also the cause of warts. There are more than a hundred sub-types of the virus, of which some may be cancer-promoting. The infections are usually localized to the superficial epidermal layer of the skin.
Patients who suffer from keratoacanthoma are at a higher risk of developing skin cancers and must take care to have any similar future lesions checked and treated immediately. Vigilance can make a big difference in managing any possible future complications.
Reviewed by Liji Thomas, MD