(See also Overview of Skin Cancer Overview of Skin Cancer Skin cancer is the most common type of cancer and commonly develops in sun-exposed areas of skin. The incidence is highest among outdoor workers, sportsmen, and sunbathers and is inversely related... read more .)
Etiology of keratoacanthoma is unknown. Most experts consider these lesions to be well-differentiated squamous cell carcinomas Squamous Cell Carcinoma Squamous cell carcinoma is a malignant tumor of epidermal keratinocytes that invades the dermis; this cancer usually occurs in sun-exposed areas. Local destruction may be extensive, and metastases... read more with a tendency to involute.
Development is rapid. Usually the lesion reaches its full size, typically 1 to 3 cm but sometimes > 5 cm, within 1 or 2 months. Common sites are sun-exposed areas, the face, the forearms, and the dorsum of the hands. Spontaneous involution may start within a few months, but involution is not guaranteed.
Diagnosis of Keratoacanthoma
Biopsy or excision
Because this lesion cannot be relied on to involute, biopsy or excision is recommended.
Treatment of Keratoacanthoma
Surgery or injections of methotrexate or 5-fluorouracil
Spontaneous involution may leave substantial scarring; surgery or intralesional injections with methotrexate or 5-fluorouracil usually yield better cosmetic results, and excision allows histologic confirmation of the diagnosis.
Prevention of Keratoacanthoma
It is unclear whether keratoacanthoma risk increases with increasing ultraviolet (UV) exposure. Because it may, a number of measures are often recommended to limit exposure.
Sun avoidance: Seeking shade, minimizing outdoor activities between 10 AM and 4 PM (when sun's rays are strongest), and avoiding sunbathing and the use of tanning beds
Use of protective clothing: Long-sleeved shirts, pants, and broad-brimmed hats
Use of sunscreen: At least sun protection factor (SPF) 30 with broad-spectrum UVA/UVB protection, used as directed (ie, reapplied every 2 hours and after swimming or sweating); should not be used to prolong sun exposure
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