Primary pulmonary/pleural melanoma in a 13 year-old presenting as pleural effusion

Melanoma in children, adolescents, and young adults is uncommon and reported almost exclusively as cutaneous melanoma. Melanoma presenting as a pleural effusion is very rare in adults and not reported in the pediatric population. Additionally, primary pulmonary melanoma is overall very rare and undocumented in pediatric patients. Furthermore, the distinction between a primary pulmonary/pleural melanoma versus a regressed cutaneous melanoma with pulmonary/pleural metastases remains extremely challenging. We discuss a case of a previously healthy 13-year-old girl that presented with a left-sided pleural effusion. Investigations revealed a large mediastinal mass, left-sided pleural and pulmonary nodules, a sacral mass, and bone marrow infiltration. The neoplasm was subsequently diagnosed by morphology and immunocytochemistry with histological correlation as malignant melanoma. As no mucosal, eye, or cutaneous lesions were identified, we deliberate the likelihood of a regressed cutaneous melanoma with metastases versus primary pulmonary/pleural melanoma with pleural effusion and discuss its diagnostic approach.