Melanoma is rare in childhood, representing no more than 2% of all skin melanomas.

Diagnosis is often delayed because melanoma is unsuspected, partly due to differences in presentation and its rarity. The diagnosis is made with trepidation by pathologists, since the vast majority of childhood skin lesions are benign.
Establishing the true prevalence of juvenile melanoma is complicated by a number of factors, one being the definition of childhood or juvenile. Many studies use a cut-off age of 19 years, but this is not consistent. Cancer registry data may also be unreliable due to misclassified Spitz naevi, for example.