Nevomelanocytic proliferations in the central nervous system of children.

Abstract

Melanocytic proliferations affecting the central nervous system (CNS) of children may be classified as meningeal melanocytosis, primary melanoma, or metastatic melanoma. Meningeal melanocytosis often is associated with giant congenital pigmented nevi (preferentially involving the midline, the head and neck) representing the lethal condition neurocutaneous melanocytosis. Primary or metastatic melanomas, although extremely rare in children, can occur in the brain and its coverings and are associated with a poor prognosis. A retrospective study of five patients with nevomelanocytic proliferations of the CNS was performed. There was characteristic enhancement in the magnetic resonance imaging (MRI) with gadolinium contrast, abnormal cerebral spinal fluid (CSF) cytology with neoplastic cells showing cytoplasmic prolongations, and nevomelanocytic proliferation in the meninges expressing HMB45 positivity and exhibiting ultrastructural features of melanocytes. Because of the rarity of these lesions, awareness of their existence is crucial for their recognition. Clinical, radiologic, and cytologic, correlation may allow an opportune diagnosis, which would allow avoidance of brain biopsy. Melanin production is not restricted to melanocytic neoplasms, and other CNS tumoral lesions occasionally may feature melanin as part of their histologic findings.