[Atypical monoclonal plasma cell hyperplasia. Infiltration of ZNS].

Atypical monoclonal plasma cell hyperplasia is extremely rare in the central nervous system without involvement of bone or other systemic disease. This neuropathological entity was first described by Weidenheim and colleagues in 1989. It is considered an inflammatory pseudotumor that can evolve into malignant myeloma. We report on an atypical monoclonal plasma cell hyperplasia with bilateral occipital and cerebellar involvement in a 38-year-old woman. The diagnosis was confirmed by brain biopsy immunohistochemical and molecular tests.