The effects of changes in health care delivery on the reported incidence of cutaneous melanoma in western Washington State.

The reported incidence of malignant melanoma of the skin has steadily increased in the United States during the past three decades. Since the treatment of melanoma increasingly has been provided solely on an outpatient basis in recent years, it is likely that some cases of this disease are being missed by population-based tumor registries that do not consistently ascertain cases from sources outside the hospital setting. The population-based tumor registry of western Washington state has been identifying office-treated cases of cutaneous melanoma from records of private and hospital pathology laboratories. However, since laboratory records have often lacked information on place of residence, these cases have not been previously included in the calculation of incidence rates. In the present study, by determining the place of residence of these cases at the time of their diagnosis (by contacting the physician listed on their pathology reports), the authors found that there had been a growing amount of underreporting of cutaneous melanoma from 1974 through 1984. In western Washington state, the incidence of melanoma of the skin had been underestimated in registry rates by approximately 2% in 1974 and approximately 21% in 1984. This trend in the level of underenumeration has spuriously blunted the true increasing incidence of melanoma and may limit the ability to monitor and study this disease in the future.