Lethal melanoma in children: a clinicopathological study of 12 cases

Melanoma in children is rare, representing 3% of paediatric malignancies and <1% of all melanomas. Very few detailed descriptions of bona fide lethal childhood melanomas exist in the literature. We performed a retrospective clinicopathological review of 12 paediatric (≤16 years) melanoma patients who died of metastatic disease, including detailed assessment of architectural and cytomorphological features. There were nine prepubertal patients (median age 7 years old) and three postpubertal cases (median age 15 years old). The patients died on average 45.7 months after diagnosis with the prepubertal subcohort showing a relatively longer time from diagnosis to death. The tumours were bulky (average tumour thickness=10mm), showed brisk mitotic activity (average mitotic count per mm²=7), and were formed by large expansile nodules with sheet-like growth pattern and infiltrative borders in the majority of cases (83%). Cytologically, large grossly pleomorphic epithelioid cells with massive eosinophilic macronucleoli were present in most cases (75%). In this cohort, we did not identify specific features of melanoma that were unique to children. Although melanomas are extremely rarely encountered in childhood, the above-cited unequivocal malignant features should prompt an outright diagnosis of melanoma even in a paediatric patient.