Malignant skin cancers in the Finnish Twin Cohort: a population-based study, 1976-97.
BACKGROUND
Both hereditary and environmental factors are implicated in the aetiology of cutaneous neoplasms. Studies of twins make it possible to estimate the contribution of inherited genes to the development of disease.


OBJECTIVE
To assess the importance of hereditary and environmental factors (including physical environment and lifestyles) in malignant melanoma and malignant nonmelanoma of the skin.


METHODS
The Finnish Twin Cohort, comprising 25 882 adult like-sexed twins with established zygosity, was linked with the Finnish Cancer Registry to identify malignant skin cancers in a prospective follow-up from 1976 to 1997. Standardized incidence ratios were computed based on national rates.


RESULTS
Sixty twins were diagnosed with melanoma and 49 twins with nonmelanoma during the follow-up. The risks of these cancers did not differ from the risk in the population at large. There was only one pair where both twins had a malignant skin cancer (dizygotic male twins both with squamous cell carcinoma).


CONCLUSIONS
The near-total lack of concordance for skin cancer in twin pairs suggests that environmental and not hereditary effects are most important in the causation of malignant skin cancers in a white population with low levels of sun exposure.
Milán
T
T
Department of Public Health, University of Turku, Lemminkäisenkatu 1, FIN-20520 Turku, Finland. tiimil@dlc.fi
Verkasalo
P K
PK
Kaprio
J
J
Koskenvuo
M
M
Pukkala
E
E
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology / Q000209:etiology / Q000235:genetics; D004200:Diseases in Twins / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D005260:Female; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease; D006801:Humans; D015994:Incidence; D008297:Male; D008545:Melanoma / Q000453:epidemiology / Q000209:etiology / Q000235:genetics; D008875:Middle Aged; D011446:Prospective Studies; D012042:Registries; D012878:Skin Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic