Primary balloon cell malignant melanoma of the right temporo-parietal region arising from meningeal naevus.

An unusual case of primary balloon cell malignant melanoma (BCMM) in brain arising from melanoblastic meningeal (or diffuse meningeal) naevus in a 30-year-old woman has been presented. The characteristic balloon cells were amelanotic or focally extremely weakly melanotic. The large, uniformly looking, tightly packed, pale "balloon cells" formed the homomorphic texture of the spherical well demarcated tumor lying in the white matter of right temporo-parietal region beneath the nevoid-looking partially melanotic diffuse meningeal and cortical infiltrate. Positive melanoma antigen HMB-45, S-100 protein and vimentin along with negative epithelial membrane antigen EMA and markers for macrophages like alfa-1-antitrypsine and CD-68 proved that balloon cells belong to and may form a peculiar type of melanoma. The lack of suspected skin or mucosal naevi and coexisting meningeal naevus speak for the primary character of the balloon cell melanoma. According to our knowledge it is the first primary balloon cell melanoma of the brain. Differential diagnosis and the pathogenesis are discussed.