Diagnostic challenges of primary diffuse leptomeningeal melanomatosis in early adolescence: A case report

Primary diffuse leptomeningeal melanomatosis is an extremely rare variant of primary melanoma of the central nervous system. It is characterized by a variety of nonspecific clinical, radiological, and histopathological features requiring differential diagnosis from a variety of diseases. Here, we aimed to use our own clinical case as an example of the difficulties in the diagnosis of this disease.

A 14-year-old boy presented with focal to bilateral tonic-clonic seizures. Brain MRI showed diffuse cortical surface and subcortical lesions, isointense on T1-weighted images and hypointense on T2-weighted images, respectively, with diffuse leptomeningeal gadolinium enhancement. Cytology of the cerebrospinal fluid revealed atypical mononuclear cells, but characteristic melanoma cells were not found. Although we suspected meningeal carcinomatosis, we did not perform abrainbiopsy under the tentative diagnosis of Sturge-Weber syndrome. A definitive diagnosis of primary diffuse leptomeningeal melanomatosis was made with abrainbiopsy after hedevelopednon-convulsive status epilepticus. Despite treatment, he died of hydrocephalus 1 year and 8 months after onset.

Primary diffuse leptomeningeal melanomatosis poses a clinical diagnostic and therapeutic challenge. Leptomeningeal enhancement extending into the cerebral sulci and signal changes in T1/T2 weighted images of cortical and subcortical lesions on MRI are key to an early decision regarding whether to perform a biopsy, even in the pediatric population.