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CLINICAL REPORT
Lethal Melanomas: A Population-based Registry Study in Western
Sweden from 1990 to 2014
Magdalena CLAESON 1 , Martin GILLSTEDT 1 , David C. WHITEMAN 2 and John PAOLI 1
Department of Dermatology and Venereology, Institute of Clinical Sciences at the Sahlgrenska Academy, University of Gothenburg,
Gothenburg, Sweden, and 2 Cancer Control Group, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
1
The incidence rates of thin melanomas (≤1 mm Bres-
low thickness) have increased in many fair-skinned po-
pulations, prompting a need to better identify patients
with thin melanomas who will eventually die from the
disease. This study aimed to describe the clinicopatho-
logical characteristics of lethal melanomas in Western
Sweden, with a focus on thin lesions. Population-ba-
sed data on invasive melanomas diagnosed during the
years 1990 to 2014 were extracted from the Swedish
Melanoma Registry, and linked to the Swedish Cause
of Death Registry. The age-standardized incidence (US
population 2000) of thin melanomas increased from
9.1×10 –5 (95% confidence interval (95% CI) 8.5–9.8)
to 21.3×10 –5 (95% CI 20.4–22.1) during the study
period. Thin melanomas comprised 55.2% of the to-
tal and contributed to 13.5% of all melanoma deaths.
Non-ulcerated melanomas 0.76–1 mm and ulcerated
melanomas 0.26–1.0 mm showed a poorer survival
compared with other thin melanomas.
Key words: cutaneous malignant melanoma; thin melanomas;
melanoma survival; histopathological subtype; ulceration; ana-
tomical location.
Accepted Jul 31, 2017; Epub ahead of print Aug 1, 2017
Acta Derm Venereol 2017; 97: 1206–1211.
Corr: Magdalena Claeson, Department of Dermatology and Venereology,
Institute of Clinical Sciences at the Sahlgrenska Academy, University of
Gothenburg, SE-413 45 Gothenburg, Sweden. E-mail: magdalena.clae-
[email protected]
C
utaneous malignant melanoma (melanoma) is a
potentially lethal tumour, arising from melanocytes
of the skin. Melanoma incidence rates have been rising
progressively in fair-skinned populations, primarily due
to an increase in thin tumours (≤ 1 mm Breslow thick-
ness) (1–5). The higher proportion of thin melanomas
has been attributed both to a true increase in melanocytic
neoplasms, as well as to the impact of early detection
and public awareness campaigns (1, 6). Melanoma
survival is strongly inversely associated with tumour
thickness, leading to excellent 20-year survival rates of
96% in patients with thin melanomas (7). Thick lesions
(> 4 mm), on the contrary, have a 20-year survival rate
of approximately 50% (8). Thus, previous research has
partly overlooked thinner tumours and instead focused on
thicker melanomas. However, a recent study has shown
that more people die from thin melanomas than from
thick lesions (> 4 mm) in Queensland, Australia, because
doi: 10.2340/00015555-2758
Acta Derm Venereol 2017; 97: 1206–1211
thin lesions have become so much more common (9).
In that study, approximately a quarter of patients who
died from melanoma were originally diagnosed with a
thin primary tumour (9). This finding shows the need to
better identify, at the time of diagnosis, the subset of pa-
tients with thin melanomas who will eventually develop
metastases from their primary tumour.
Sweden has a fair-skinned population that expe-
riences a high incidence of melanoma, and a high cost-
to-population ratio for skin cancer (5, 10). Not only is
the incidence high; male age-standardized rate (ASR)
39.7×10 –5 , female ASR 35.3×10 –5 (Swedish population
year 2000), but the annual percentage increase is also
greater than 6% (11).
Sweden has a tradition of well-kept cancer registries
with high coverage rates, facilitating epidemiological
registry studies (12). The western parts of Sweden have,
for the past decades, shown a higher incidence of mela-
noma than the national average, and projections show
that this geographical area can anticipate greater numbers
of melanoma in the future (13, 14). A few studies have
investigated thin melanomas in Sweden, but none have
focused on Western Sweden (4, 15–17). The aim of this
study was to describe the clinicopathological characteris-
tics of lethal melanomas in Western Sweden during the
years 1990 to 2014, with a focus on thin lesions (≤ 1 mm).
METHODS
In Sweden, there are 6 regions for the organization and quality
control of cancer healthcare, each with a centre responsible for
the prospective registration of tumours in the Swedish Melanoma
Registry. The Regional Cancer Centre West collects clinicopatho
logical data on melanoma patients from the “Western Sweden
healthcare region”, which corresponds geographically to the
county of Västra Götaland and the northern parts of Halland
county. These regions have approximately 1.8 million inhabitants,
corresponding to 1