Clinical history analysis of Japanese melanoma cases and characteristics of melanoma with childhood onset.

It remains debatable whether melanoma with a clinical history of early childhood onset truly arises from a nevus. To clarify the clinical and genetic characteristics of melanoma detected at birth or several years afterwards, 249 melanoma cases seen at Shinshu University Hospital between 2006 and 2015 were retrospectively analyzed. Ten (4.0%) cases (median age 39.5 years, range 19-70 years; male/female 2/8; lesion site, 6 extremities, 2 trunk, 1 head, 1 face; cumulative sun damage [CSD] skin, 9 low-CSD, 1 high-CSD; detection at birth 3) had recorded early childhood onset. Median Breslow's tumor thickness in those cases was 6.0 mm (range: 0.4-17.5 mm). The frequency of lesions detected at <20 years of age was significantly higher for low-CSD melanoma (17.5%) than for high-CSD (3.3%) and acral (0.8%) melanoma. Although melanoma with a history of early childhood onset is rare, the characteristics of such cases should be established since most have progressed to an advanced stage at the initial visit.