In the diagnosis of melanocytic lesions, it has not been fully established whether a clinical history of early childhood onset is sufficient to differentiate melanoma from congenital melanocytic nevus in adults. To clarify this point, 253 histopathologically proven adult cases of melanoma primarily developing on the skin and examined at Shinshu University Hospital between 2006 and 2015 were retrospectively reviewed. Melanoma arising from giant congenital melanocytic nevus was excluded. We selected patients who were identified as having a lesion at birth or in early childhood and evaluated their clinical, histopathological, and genetic findings. Oncogenic BRAF mutations were analyzed by the Sanger method. Ten (3.95%) of 253 melanoma cases satisfied the above clinical history, including 3 lesions found at birth. Among the 10 cases (median age: 39.5 years; 2 male and 8 female), the lesion was located on the extremities in 6 patients, on the trunk in 2 patients, and on the head and face in 1 patient each. Histopathological examination revealed that 9 lesions had developed on non-chronic sun-damaged (CSD) skin. The oncogenic BRAFV600E mutation was positive in 6 patients, negative in 2 patients, and undetermined in 2 patients. Our findings indicated that cutaneous melanoma with a clinical history of early childhood onset most frequently developed on non-CSD skin. Other characteristics, such as prevalence on extremities, young female predisposition, and positivity for the oncogenic BRAFV600E mutation, were common with melanoma occurring on non-CSD skin. Although the clinical history provided by patients is not always reliable, melanoma cannot necessarily be ruled out by a history of early childhood onset.

Clinical and genetic characteristics of cutaneous melanoma with clinical history of early childhood onset