Melanoma in Kauai, Hawaii, 1981-1990: the significance of in situ melanoma and the incidence trend.

Background: The incidence of melanoma has often been portrayed as reaching 'epidemic' proportions. The reality of such an epidemic is, however, not clearly established due to the methods of data collection and interpretation. The population-based incidence data and incidence trend of melanoma from the Island of Kauai, Hawaii provide an illustration of this 'epidemic'.

Methods: We used medical records housed at the dermatology clinic and pathology laboratory in Kauai to: identify residents of Kauai who had their first melanoma during the years 1981-1990; and to measure the 10-year population-based incidence of melanoma.

Results: In Caucasians: A total of 53 Caucasian residents (29 men and 24 women), were identified with an initial episode of melanoma (MM) during the 10-year period. The average annual standardized incidence rate per 100,000 Kauai Caucasian residents was 36. Whereas the incidence of in-situ MM increased during the 10-year period, the incidence of invasive MM did not. The average patient age was 55 years. The trunk and the limbs were the most common anatomic sites of MM. In men, one third of MM occur on the back. In women, one third develop on the leg/thigh. Three patients (6%) had metastasis and eventually died of MM. Thirteen patients (25%) had other skin cancers such as basal cell carcinoma and squamous cell carcinoma at some time. In Filipinos, Japanese and Hawaiians: Three Filipinos (all women), two Japanese (one man and one woman) and one Hawaiian (man) had melanoma. The standardized incidence rates, to the U.S.A. Caucasian population, were 3.1, 0.8 and 2.1 per 100,000 residents, respectively.

Conclusions: The melanoma incidence in Kauai is one of the highest rates documented in the U.S.A. However, a decreased incidence of invasive melanoma during the 10-year period was unexpected. The finding of nonmelanoma skin cancer in these patients supports a common etiology among these skin cancers.