Recent incidence trends imply a nonmetastasizing form of invasive melanoma.

In the mid- to late-1980s white populations in Australia, New Zealand and Scotland showed a sharp increase in melanoma incidence above preceding long-term trends, in some cases as much as doubling in as little as 2 years. Most of this increase was in thin melanomas, (< 1.50 mm thick), and males were more affected than females. Thicker melanomas also generally increased in incidence, particularly in males aged 65 years or older. Examination of Australian Medicare and pathology laboratory data indicated that excision of skin lesions and laboratory diagnosis of pigmented lesions also rose sharply in this period, suggesting that advancement of the time of diagnosis was a likely factor in the increase in melanoma incidence. However the maintenance of new higher incidence levels and the increase in incidence of thicker lesions suggests that advancement of diagnosis cannot explain all of the increase. A real increase in incidence and increasing diagnosis of a preexisting, non-metastasizing form of thin melanoma may also have contributed.