Amelanotic Meningeal Melanoma with Leptomeningeal Dissemination: A Case Report and Systematic Literature Review.

BACKGROUND: Meningeal melanoma is a rare tumor of the central nervous system, whose amelanotic variant is the so-called 'amelanotic meningeal melanoma (AMM)'. AMM does not produce melanin and therefore does not exhibit typical short-T1 and short-T2 signal on MRI, and thus can be easily misdiagnosed and be inappropriately managed. To date, only four AMM cases were reported in English literature, here we reported the fifth case.

CASE DESCRIPTION: A 26-year-old female presented with a 4-month history of progressive headache and nausea, the conventional MRI demonstrated a posterior fossa mass accompanied by diffuse leptomeningeal dissemination. Repeated cerebrospinal fluid cytology screening showed negative results. The functional MR examinations including diffusion weighted imaging (DWI), proton MR spectroscopy (1 H-MRS) and dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI) provided complementary information. The final diagnosis of amelanotic meningeal melanoma was made by immunohistochemistry. Despite gross total excision of the tumor, the disease progressed, and the patient died 10 months after diagnosis.

CONCLUSIONS: Our experience with this case demonstrated that meningeal melanoma should be included in the differential diagnosis when an intracranial mass is accompanied by leptomeningeal dissemination, and especially when 1 H-MRS and DSC-PWI indicate a malignant tumor whereas DWI does not. And the loss of a typical melanin signal should not server as an excluding criterion for meningeal melanoma.