What is Keratoacanthoma?
Keratoacanthoma is a skin growth described as low-grade tumor or that which do not metastasize. It resembles the squamous cell carcinoma that some believe it be the variant of squamous cell carcinoma. This type of skin tumor is believed to be prompted by the hair follicle of the neck.
The skin tumor in keratoacanthoma usually affects areas of the skin that are in constant exposure to the sun. These areas of the skin exposed to the sunlight include the face, forearm and the hands. Keratoacanthoma is also marked by the rapid growth of skin tumor in a matter of a few months and usually resolves spontaneously within 4 to 6 months in most cases reported.
Keratoacanthoma can affect all people although it is prevalent among white skinned individuals and rarely occurs in dark skinned people. The peak onset of keratoacanthoma is during the 7th decade of life and rarely affects people under the age of 20 years. It is more common in male gender than in female gender and can occur without racial predilection.
The prognosis for keratoacanthoma is relatively good but was later reclassified as "squamous cell carcinoma-keratoacanthoma type" due to the difficulty in identifying the histologic differentiation including the rare aggressive characteristic of keratoacanthoma. Keratoacanthoma on the other hand seldom presents in multiple growths and rarely metastasize although it may potentially increase in size.
The hallmark of keratoacanthoma is its rapid growth to an inch within a few weeks, although may potentially increase in size. The rapid growth of the tumor is followed by a steady stationary period the slowly regresses over the period of 2 to 6 months. Keratoacanthoma may also metastasize although this rarely occurs.
The most common site for keratoacanthoma is the face and the neck and may also occur in the areas of the skin that are in constant exposure to the sunlight such as the forearm and the hands. The tumor in keratoacanthoma is characterized by a round shape during the initial onset with a smooth texture and is firm to touch and accompanied with a reddish or skin tone discoloration. As the keratoacanthoma progresses, it assumes a dome shape and is rather smooth and shiny surface. The center of the nodule is presented with an ulceration or keratin plug that resembles a horn. The core of the nodule is dark in color while the nodule may be skin colored or may be pink-reddish in color. The skin surrounding the nodule on the other hand retains its normal color.
The exact cause of keratoacanthoma remains vague although several factors potential for the onset of the skin tumor have been considered. Keratoacanthoma is noted to have similar etiology with squamous cell carcinoma with regards to the age during the onset, gender and the site of nodules.
The growth of tumors on the skin surface is being linked to the error in the DNA of the outer layer of the skin. Normally, the skin sheds dead skin cells that are pushed from the skin surface of the new cells that are formed in the normal process. The disruption in the process of skin regeneration is believed to lead to tumor growth as a consequence of the accumulation of old skin cells that are not pushed outside the skin surface.
The major implication in keratoacanthoma is damage to the DNA of skin cells resulting from exposure to ultraviolet rays of the sun. The unprotected and prolonged exposure under the sun is greatly implicated in the development of keratoacanthoma. Ultraviolet radiation found in commercial tanning lamps and tanning beds also contribute to the onset of keratoacanthoma especially if this is done habitually.
Risk factors potential for Keratoacanthoma include the following:
- Prolonged exposure under the sun is the most implicated risk factor in keratoacanthoma. Prolonged and unprotected exposure under the sun puts an individual at risk for skin damage which can lead to keratoacanthoma and other squamous cell carcinoma.
- Fair skinned individual has less melanin in the skin which protects them from the harmful effect of the sun. Dark skinned individuals have more melanin in the skin that makes them less prone to skin damages.
- Occupational factor is also considered at the onset of keratoacanthoma. People exposed to chemicals such as tar and pitch have a high risk for keratoacanthoma. Farmers, gardeners and other works that require prolonged exposure under the sun are at risk for developing the skin tumor as well.
- Weakened immune system individuals have a high risk for developing keratoacanthoma and other squamous cell carcinoma.
- Medications meant to suppress the immune system can put an individual taking it at higher risk for developing keratoacanthoma and any other form of skin tumor.
- Male gender is commonly affected with keratoacanthoma which is found to be twice higher than the female gender.
- Age is also another risk factor for keratoacanthoma. The peak onset of the skin tumor is on the 6th to 7th decade of life and rarely occurs in people younger than the age of 20.
The initial step in diagnosing keratoacanthoma is through physical examination and taking the medical history of the patient.
Physical examination should reveal the characteristic of the keratoacanthoma lesion. The lesion should present as elevated and fleshy with central hyperkeratotic core. The initial stage of keratoacanthoma usually has a round shape with smooth texture and is firm to touch. Keratoacanthoma that progresses assumes a dome shaped lesion that is smooth and shiny and firm to touch.
Medical history taking should consider the apparent changes in the skin appearance. It should also include previous exposures and underlying conditions that triggered the onset of keratoacanthoma.
A deep punch biopsy is beneficial in confirming the development of keratoacanthoma. This form of skin biopsy can differentiate keratoacanthoma from squamous cell carcinoma.
Keratoacanthoma usually resolve spontaneously in a matter of 2 to 6 months. Treatment may be needed to avoid potentials for malignancy and for cosmetic concern as well. The growth of keratoacanthoma is unsightly and can be annoying.
Removal is the option for treating Keratoacanthoma and this includes the following:
Freezing or cryosurgery is removing the skin tumor with the use of liquid nitrogen by freezing the tumor. This is usually an option for superficial skin lesions that need not go deeper into the dermis and need to incise the affected site.
Electrodessication and curettage is the process that involves scraping out the tumor with a curette and burning the base with an electric needle.
Mohs surgery is recommended for tumor growth on the nose and face. This procedure allows for minimal tissue removal with tissue removal done layer by layer and with each removed layer being examined under the microscope to determine the remaining cellular aberration.