Prepubertal melanoma in a medium-sized congenital naevus.

A case of malignant melanoma in a medium-sized congenital naevus in a prepubertal girl is presented. Risk factors for developing melanoma during childhood include giant congenital naevi, dysplastic naevus syndrome and xeroderma pigmentosum. The lifetime risk of melanoma associated with giant congenital naevi has been estimated to be 4%-20%; the risk associated with small and medium-sized congenital naevi however remains controversial. In the latter lesions, malignant transformation is considered an almost exclusively postpubertal phenomenon, in contrast to giant congenital naevi where it often occurs prior to puberty. In our patient, malignant transformation in a medium-sized congenital naevus occurred before puberty. We suggest that the true incidence of malignant transformation within these lesions and the time at which it occurs, should be documented by prospective studies and that not only the giant congenital naevi but also the smaller congenital naevi should be considered for prophylactic excision in early childhood.