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Keratoacanthoma – Pictures, Symptoms, Causes, Treatment

Written by Dr.Mary

What is Keratoacanthoma?

Keratoacanthoma or KA is a skin growth that is reasonably common and is swiftly growing. It typically appears as a dome-like lump on skin which is sun-exposed on light-skinned elderly as well as middle-aged individuals. It is frequently found at sites of prior trauma or injury. Many researchers believe that keratoacanthomas is the less severe type of “squamous cell carcinoma”. Most keratoacanthoma cause only nominal injury to the skin but some do act more antagonistically and can spread to lymphatic nodes. It is not associated with internal malignancy except in instances which are very rare and where multiple keratoacanthomas are linked with a disease process known as Muir-Torre syndrome.

Keratoacanthoma Symptoms

The more likely positions for keratoacanthoma consist of:

  • Backs of hands
  • Face in the center
  • Ears
  • Forearms
  • Especially in women, lower legs
  • Scalp

A keratoacanthoma becomes visible and develops quickly over the course of 2 to 6 weeks. Beginning as a pimple-like, small lesion, a keratoacanthomas normally grows into a dome-shaped, skin-colored bump with a depression in the center that is packed with keratin (which is the main protein in skin, nails as well as hair). Keratoacanthomas normally vary in size from 1 to 2.5 cm. They normally shrink in 6 months and that pushes out the plug in the center, leaving behind a depressed scar.

In some rare cases, numerous keratoacanthomas can increase as part of a larger collection of symptoms.

The majority of keratoacanthomas cause no pain, although there are several which are very itchy. Depending on the site of concern keratoacanthoma can impede the normal purpose of the area which is affected.

Keratoacanthoma Causes

With keratoacanthomas, past exposure to the sun seems to be the major contributing factor. They seem to arise from a single hair follicle since they are only seen on hair-bearing skin and not on the palms. Various chemicals can also cause KAs.

Some sort of minor injury seems to be needed to trigger a keratoacanthomas to start growing but this is either not remembered by the individual or not apparent. The cells begin multiplying in the hair follicle and the mass grows into a keratoacanthomas.


There are some keratoacanthomas which appear to be linked to an infection with human papilloma virus that causes warts.

Left untreated, a true keratoacanthoma will continue to grow for several months, reach a maximum size and then begin to self-destruct over the next several months. Unfortunately a keratoacanthoma often looks like a true skin cancer, a squamous cell carcinoma or rarely a basal cell carcinoma; therefore it should be seen by the primary care physician.

Keratoacanthoma Treatment

If your primary care physician believes that the lesion is a keratoacanthoma, he/she will initially want to begin with the accurate diagnosis by completing a biopsy. This course of action involves:

  1. Numbing the skin with anesthetic which is injectable
  2. Sampling a tiny section of skin using a bendable razor blade, scalpel or a “punch biopsy”. When using a “punch biopsy”, a stitch or suture or 2 may be required and it will be needed to be taken out in 1 to 2 weeks later.
  3. Have a dermatopathologist examine the sample of skin under a microscope.

When the diagnosis of keratoacanthomas is established, the treatment options normally include:

  • Freezing with nitrogen in liquid form which is known as cryosurgery, in which this cold liquid nitrogen is sprayed on the keratoacanthoma. This process freezes and destroys the lesion.
  • Excision where the doctor uses a knife-like instrument to cut out the keratoacanthoma and then use stitches to bring the edges of the wound together.
  • Electrodesiccation and curettage also known as “scrape and burn”. After numbing the lesion, the physician utilizes a sharp instrument to “scrape” the skin cancer cells away, trailed by an electric needle to “burn” the lesion tissue. The electrodesiccation helps to eradicate the cancer cells as well as also impede any bleeding at the site.
  • Mohs micrographic surgical procedure where the physician takes tiny shavings of skin from the cancer site until it is totally removed. This method is especially useful for keratoacanthoma situated on the ears, the nose, the hands as well as the lips.
  • Radiation management, for those patients who could have difficulty with a surgical process because of any health issues.

Rarely, keratoacanthoma can be treated with medicine injected directly into the skin lesion which is known as intralesional chemotherapy. Also in those patients with more than 1 keratoacanthoma, the doctor might suggest taking a pill of isotretinoin in order to reduce there number and size.

Finally, it is important to know that treatment of keratoacanthomas is not finished once the skin cancer has been removed. There will be numerous follow up appointments with a dermatologist or with a physician trained to examine the skin as it is vital to make sure that the keratoacanthoma has not returned as well as making certain that any new skin cancer has not developed anywhere else on the body. Additionally, good sun protection habits need to be developed so as to prevent further damage from UV light.

Keratoacanthoma Pictures

  1. What chemicals could be the cause of Keratoacanthoma? Does the exposure have to be recent?

  2. What would cause a keratoacanthoma to develop under a toenail?

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