Medically reviewed by Dr. A.M. van Coevorden, dermatologist
Keratoacanthomaa fast-growing lump with a horny plug, a low-grade form of skin cancer
A keratoacanthoma is a fast-growing lump on the skin with a horny plug in the centre, regarded as a low-grade form of squamous cell carcinoma. An untreated keratoacanthoma usually goes away on its own after a few months, leaving a small scar. Because it cannot be distinguished from a malignant squamous cell carcinoma under the microscope, it is often treated anyway.
What is a keratoacanthoma?
A keratoacanthoma is regarded as a special form of squamous cell carcinoma. Characteristic is a fast-growing lump with a horny plug in the centre. An untreated keratoacanthoma generally goes away on its own after a few months, leaving a small scar.
How do you get a keratoacanthoma?
The main cause is frequent and prolonged sun exposure. Keratoacanthomas appear almost only on skin that gets a lot of sun, such as the face, ears, arms and hands. Usually it is a single spot; in rare cases there are several.
What does it look like?
A keratoacanthoma looks like a small lump in skin colour or light red, often with a horny plug in the centre, and feels rough. The lump typically grows quickly within a few weeks and can reach several centimetres. After a few months it should shrink and disappear on its own, leaving a scar. It can be painful or tender, but need not be.
Is a keratoacanthoma contagious?
No. A keratoacanthoma is a form of skin cancer and cannot be passed from person to person.
How is the diagnosis made?
Sometimes the dermatologist makes the diagnosis from the history and appearance, but this is often difficult because it resembles a squamous cell carcinoma. A biopsy often does not help either, because the pathologist sees no clear difference under the microscope between a keratoacanthoma and a malignant squamous cell carcinoma. That is why a keratoacanthoma is regarded as a low-grade, more benign form of squamous cell carcinoma.
What treatment is there?
A keratoacanthoma usually goes away on its own, but because that can take a long time and a malignant squamous cell carcinoma cannot be ruled out, it is often treated anyway. Surgical removal (excision) under local anaesthetic is the first choice, by the dermatologist or sometimes a surgeon.
Do you need follow-up?
When in doubt, a keratoacanthoma is treated as a low-grade squamous cell carcinoma, with at least five years of follow-up. Sometimes there is no doubt and the dermatologist opts for fewer checks, although follow-up appointments are often still planned. Because a keratoacanthoma develops from sun exposure, you are at risk of a new skin cancer spot elsewhere.
What can you do yourself?
After treatment, check your whole skin yourself, with extra attention to the treated area. If a lump or wound appears that does not clear within a few weeks, make an appointment promptly and do not wait; pain and rapid growth are reasons to make contact sooner. Avoid sunburn and do not use a sunbed.
Frequently asked questions about keratoacanthoma
Is a keratoacanthoma skin cancer?
It is regarded as a low-grade, more benign form of squamous cell carcinoma. Because it cannot be distinguished from it under the microscope, it is often treated as skin cancer.
Does it not go away on its own?
Usually it does, after a few months, leaving a scar. But because that takes a long time and a malignant form cannot be ruled out, it is often removed anyway.
How do I recognise it?
By a fast-growing, round lump in skin colour or red with a horny plug in the centre, usually on sun-exposed skin. Always have a fast-growing lump assessed.
How is it treated?
Usually by cutting out (excision) under local anaesthetic.
Do I need follow-up?
Often yes, usually five years, because sun damage raises the risk of a new skin cancer spot elsewhere.