Primary malignant melanoma of skin in four regions of New Zealand.

AIMS: to describe the incidence and thickness of a representative collection of melanomas occurring in recent years in New Zealand. METHODS: all pathology reports of primary malignant melanoma of the skin, in defined periods in 1987-9, were collated for four regions of New Zealand. RESULTS: nonMaori incidence rates were 52 and 58 melanomas per 100,000 person years for men and women, respectively. These rates are much higher than the 24 per 100,000 person years for melanoma registrations in 1983-4. The age standardised invasive melanoma rate of 35 per 100,000 person years was higher than those of most Australian states and close to the rate for Queensland in 1986. Preinvasive melanomas comprised 26% of all melanomas. Of invasive melanomas, 58% in men and 55% in women were less than 0.76 mm in thickness; 7% of invasive melanomas in men and 5% in women were at least 3.5 mm thick. CONCLUSIONS: increasingly early detection of malignant melanomas in successive years is likely to have contributed to the recent increase in incidence, perhaps to a major degree, but an environmental cause cannot be excluded.