What Is Keratoacanthoma?

With a keratoacanthoma, you develop a red bump or dome on your skin that may resemble a horn. Most cases are seen in older adults. While it may be confused with squamous cell carcinoma (a type of skin cancer), keratoacanthomas have little or no risk of spreading to other parts of the body. You may develop just one, or less commonly, you can have several.

But only some see this as a distinct lesion. There is also some controversy over whether keratoacanthoma may be a form of squamous cell carcinoma or may evolve into this.

This article will discuss the different types of keratoacanthoma, its symptoms, causes, diagnosis, treatment, and more.

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Types of Keratoacanthoma

Different types of keratoacanthoma include acantholytic, clear cell, epidermolytic, and melanoacanthoma. Here's what to know about each.

• Acantholytic acanthoma is a single bump found on the trunk of the body. It usually occurs in older people and is typically painless.
• Clear cell acanthoma usually involves a single reddish or brownish dome-shaped lesion. These lesions are often biopsied (a sample taken and analyzed in the lab) to rule out other skin malignancies.
• Epidermolytic acanthoma usually occurs in the genital area. The lesion is usually a small skin-colored lesion, which may occur on its own or in clusters.
• Melanoacanthoma is usually found on an older person's trunk, head, neck, or eyelid. It tends to occur more commonly in light-skinned people.

Keratoacanthoma Symptoms

You can usually find an acanthoma lesion on areas of the body that are exposed to the sun, such as the face, trunk, arms, or legs. The bump is commonly a smooth, flesh-colored dome. In the center, it has a keratin core (the protein that forms your nails and hair). It is painless.

These lesions may start as a small bump of 1 to 2 millimeters in size and rapidly grow to be 1 to 3 centimeters over a one- to two-month period. They commonly stop growing and slowly shrink away after two months to a year.

Keratoacanthomas commonly disappear on their own. In some cases, they may leave a scar.

Causes

Although the exact cause is not known, sun exposure is thought to be involved in the development of keratoacanthoma lesions. Other possible causes can include:

• An human papillomavirus (HPV) infection
• Genetic predisposition
• A compromised immune system
• Skin injury
• Chemical exposure

Diagnosis

You may visit your healthcare provider when you note symptoms of keratoacanthoma, and they may refer you to a dermatologist (a specialist in skin conditions).

The fact is that there is controversy over whether keratoacanthoma is a unique non-cancerous lesion that can resolve on its own or is a form of cancer. Some believe it is either a precursor or a variant of squamous cell carcinoma or cancer that is self-limiting and occasionally progresses to squamous cell carcinoma.

To try and determine if you have a keratoacanthoma lesion, they will ask you a few questions about how the lesion emerged before examining this nodule.

These lesions typically are smooth and symmetrical and appear dome-shaped. Although, in some cases, these can be cup-shaped with some ulceration in the center. If these are located on the eyelids or nose, tissue in the area can be destroyed.

To help determine if this is a keratoacanthoma lesion, the lesion will be biopsied, where a piece of the tissue is removed and examined in the lab for signs of cancer. They can explore the structure of the tissue (histology) and see if this is in keeping with keratoacanthoma lesions.

Even with the diagnostic options, it can be difficult to distinguish between keratoacanthoma and squamous cell carcinoma. Sometimes these can clinically mimic each other.

For example, keratoacanthoma is typically known for its rapid growth, but sometimes a squamous cell carcinoma can follow a similar rapid course, especially if the immune system isn't working correctly.

Treatment

Because it can be challenging to determine whether this is a keratoacanthoma lesion or a squamous cell carcinoma, it's essential to remove the lesion. The standard approach to dealing with such lesions is to remove or destroy them somehow. Treatment can include the following:

• Cryotherapy (cold therapy) with liquid nitrogen can freeze the tissue and remove the lesions.
• A surgeon can numb the area and excise the lesion using a scalpel.
• Electrodesiccation and curettage involve burning and scraping away the tissue.
• A Mohs procedure can be done in which the tissue is surgically removed in stages and analyzed for any signs of cancer as the tissue is removed.
• Radiation therapy can be applied to the lesion.
• Chemotherapy drugs such as Efudex (5-fluorouracil), Dermotrex (methotrexate), and Bleo 15K (bleomycin) can be applied to the skin or injected in some cases.

Prognosis

If you are dealing with a keratoacanthoma that is a benign (noncancerous) lesion, your prognosis is very good. The growth may regress on its own, although it may sometimes leave a scar.

Likewise, if this is a squamous cell carcinoma confined to the area, you should do well with treatment. But if this has spread elsewhere in the body, you may be facing a serious prognosis.

Summary

If you develop a keratoacanthoma, a bump or dome with a central core has appeared somewhere on your skin. Usually, this is an area exposed to the sun, such as your head, neck, eyelid, back of the hand, or arm or leg. These are usually noncancerous, although they can be confused with squamous cell carcinoma. Some also think that acanthoma is a variant of squamous cell carcinoma.

Because it may be unclear whether the lesion is a squamous cell carcinoma and may spread, this should either be removed or destroyed with surgery, cryotherapy, radiation, and other procedures.

A Word From Verywell

While a keratoacanthoma lesion may stand out, the good news is that these are usually noncancerous and will often go away on their own. If you decide to have it removed, you will have various options. Even if this does turn out to be cancerous, as long as your dermatologist treats this early, you should do well.