Malignant melanoma is the least common but most serious type of
skin cancer. Early diagnosis usually results in timely surgical
treatment and cure. Education and prevention are the most important
aspects in the management of melanoma.
There has been a world-wide increase in the incidence of melanoma
over the last four decades. In New Zealand, the incidence and
mortality rates have increased dramatically since 1960. Until
recently Australia was considered to have the highest incidence of
melanoma in the world with the highest rates being recorded in
Queensland at 50/100,000/y (50 new cases per 100,000 population per
Auckland is in the northern part of New Zealand at latitude
37¬¨¬®? S and receives on average 2100 sunshine hours per year. The
region contains one third of the population of the country. The true
incidence of malignant melanoma in Auckland is not known, although it
is thought to be high. The aim of our study was to document the
incidence of melanoma in the Auckland Caucasian population. This
disease is rare in Maori, Polynesian and Asian races and mainly
affects people of European descent.
A list of all cases of invasive cutaneous malignant melanoma
registered in 1995 from the Auckland region was obtained from the New
Zealand Cancer Registry. Cases of in-situ (non-invasive) melanoma
This data was combined with cases from 1995 collected by the
Auckland Melanoma Unit. The AMU database consists of clinical,
pathology and treatment details of 2500 patients with melanoma
managed from 1970 to 1999.
Statistics from the 1991 and 1996 New Zealand Census were used to
derive a population estimate for the Auckland region based on
domicile in 1995. People identified as non-Caucasian (NZ Maori,
Pacific Islanders and Asians) were excluded from the census figures
and from the melanoma data-set. The resultant incidence figures were
calculated for the Caucasian population only.
There were 525 reported new cases of invasive malignant melanoma
in 1995 in the Auckland region. The total population for Auckland in
1995 was calculated as 1,055,813. Of these, 64% of residents were
Caucasian. Therefore, the overall crude incidence of melanoma amongst
the Caucasians was 77.7/100,000/y. The rate was higher in males at
78.5 than females at 76.8/100,000/y.
The cumulative risk of developing melanoma, over a lifetime from
age 0 to 74, assuming no other causes of death are in operation, was
5.9% for males and 5.4% for females.
The average age at diagnosis for males was 59 years and for
females, 54 years. The rates for melanoma steadily increase with
advancing age in both sexes. Melanoma is rare under 15 years of age,
however in the eighth decade of life the age specific rate approaches
200/100,000/y in females and 300/100,000/y in males.
With regard to body site; the trunk is the most common site,
followed by the lower limbs, upper limbs and then the head and neck.
There are significant gender differences, with the trunk and head and
neck being more common sites in males, and the lower limbs more
common in females.
The high incidence of melanoma in Auckland is probably due to
out-door recreational activities and inadequate sun protection.
Intermittent sun exposure and 'sunburn', particularly in childhood,
is now well established as a causative factor in the development of
The recent increase in incidence of melanoma in Scotland,
Australia and New Zealand has been largely due to the diagnosis of
more thin lesions. This is encouraging and suggests earlier diagnosis
as a result of improved surveillance and education. Despite the high
proportion of thin lesions, there are still thick melanomas being
diagnosed, particularly in the head and neck region and in the
It is hoped that with public education and improved sun exposure
behaviour, the rates should decrease in the longer term. However,
with the effect of local stratospheric ozone depletion and the time
lag from sun exposure to melanoma development, the incidence of
melanoma in this part of the world may continue to rise well into the
In conclusion, Auckland, New Zealand has the highest documented
incidence of invasive malignant melanoma in the world, with a crude
rate of 77.7/100,000/y. The cumulative risk of developing melanoma in
a lifetime is a staggering 5.7%.
The full text of this article was published in the July 1999 issue
of the World Journal of Surgery:
Jones WO, Harman CR, Ng AKT, Shaw JHF. Incidence of malignant
melanoma in Auckland, New Zealand: The highest rates in the world.
World J Surg 1999; 23(7): 732-5.
Dr Wayne Jones
- Surgeon, Auckland Hospital
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