Malignant melanocytic lesions of unknown primary site in children and adolescents

Metastatic melanoma with an unidentified primary site represents 4% of all newly diagnosed cases of malignant melanoma in adults. Little is known of the incidence and clinicopathologic features of this clinical entity in the pediatric population.

We reviewed all previously diagnosed cases of malignant melanoma in children and adolescents (< 21 years) who were treated at our institution and identified three patients who presented with metastatic melanocytic lesions with an unidentified primary site.

This clinical presentation accounted for 9% of all malignant melanocytic lesions treated at our center over a 20-year period. The clinicopathologic features were similar to those seen in adults. Two patients died of progressive disease within two years of presentation; the third is alive and disease-free 18 years post-diagnosis.

Although uncommon in the pediatric population, malignant melanoma should be considered in the differential diagnosis of poorly differentiated disseminated malignancy that involves lymph nodes or viscera with no identifiable primary tumor.