Keratoacanthoma in Kauai, Hawaii. The first documented incidence in a defined population.

BACKGROUND AND DESIGN: A prospective 5-year population-based incidence study was conducted on the island of Kauai, Hawaii, from 1983 through 1987 to investigate the frequency of keratoacanthoma in white residents.

RESULTS: A total of 53 residents, 36 men and 17 women, were identified with an initial episode of keratoacanthoma during the 5-year study. The average annual incidence rate per 100,000 Kauai residents, standardized to the US white population, was 144 for men and 73 for women, with a combined rate of 104. The average patient age was 63.5 years. The limbs, particularly the hands and arms, were the most common anatomic site, with the trunk second. Only one patient developed a new subsequent keratoacanthoma, and no recurrent lesions were observed. Three patients had two keratoacanthomas when they first presented, and 13 patients had concurrent skin cancer. Sixty percent (32) of our patients developed skin cancer at one time or another.

CONCLUSIONS: We report the first population-based keratoacanthoma incidence rates documented in the United States, which are almost equal to those of squamous cell carcinoma. Keratoacanthoma also shares many common epidemiological features with squamous cell carcinoma, such as increasing incidence in progressively older age groups.