Malignant melanoma in children and adolescents

Sammanfattning: The aim of the work reported in the present thesis was to investigate malignant melanoma in children and adolescents. Through epidemiological studies, we wished to investigate incidence, clinical factors and prognosis and to study the records. Also studied were etiological factors such as phototherapy in newborns and the effect of congenital nevi on the risk of malignant melanoma. Finally a genetic study of this age group was conducted using immunohistochemical analysis. The bases for the studies were the Swedish Cancer Register, the Swedish Medical Birth Register and other related registers. The incidence of malignant melanoma in children was constant, but in adolescents a doubling was seen for the past few decades. The most common type of malignant melanoma in adolescents is the superficial spreading type, the one most likely to be sun-related. Since the anatomical location is the same in adolescents as in adults, the same etiological factors are presumably of importance; but some other factor may reduce the induction time. For this reason, diagnosis is set at a median age of 55 in adults compared to 15 in adolescents. Median survival time was three years after diagnosis, 15.3% of patients dying as a result of the diagnosed condition, most around 20 years of age. No specific anatomical location was overrepresented as fatal. Phototherapy of newborns has probably been ruled out as a factor in the increased incidence of malignant melanoma: on the contrary phototherapy may well be a protective factor just as outdoor activities in childhood are. Congenital nevi are often surgically removed unnecessarily; no malignant melanoma was found after histopathological review of nearly 4000 congenital nevi. It must be considered whether the reason for removal is the risk of malignant transformation or is merely cosmetic. Further, no clear association was found between congenital nevi and maternal illness/infection during pregnancy. Congenital nevi seemed to have had limited effects on social life, but had resulted in greater caution with regard to sun exposure. Congenital nevi or their treatment seem to play no part in the increased incidence of malignant melanoma below the age of 20 years. We found only one patient in 51 with adolescent malignant melanoma with a germline CDKN2A mutation. It is therefore likely that other genetic factors are of importance for the development of malignant melanoma in adolescents. Knowledge of risk factors for the development of malignant melanoma, and of its early clinical characteristics, should as a matter of importance be spread to the medical profession and also to the general public.