Histiocytic tumours of the central nervous system

Abstract

Abstract Histiocytoses are heterogeneous neoplasms of the haematopoietic system characterized by the accumulation of histiocytes with variable inflammatory infiltrates. The identification of the crucial role of the mitogen-activated protein kinase (MAPK) pathway has opened the door to new targeted therapies. This chapter reviews the central nervous system (CNS) manifestations and treatment of six histiocytic disorders: Langerhans cell histiocytosis (LCH), juvenile xanthogranuloma (JXG), Erdheim–Chester disease (ECD), Rosai–Dorfman–Destombes disease (RDD), and histiocytic sarcoma (HS). CNS involvement occurs in 10–25% of LCH cases and can manifest in tumorous or neurodegenerative forms, which can have different clinical, radiographic, and prognostic implications. Intracranial JXG accounts for 2% of all JXG cases, is more common in males, and is usually leptomeningeal, with frequent concurrent systemic disease. Almost 40% of ECD patients can present with tumourous or neurodegenerative manifestations, and this can affect the brain parenchyma, leptomeninges, and hypothalamic–pituitary axis. RDD CNS lesions are usually tumourous, with meningeal or parenchymal masses without neurodegenerative lesions. Refractory CNS histiocytic neoplasms should lead to the consideration of targeted kinase inhibitor therapies such as BRAF/MEK or ERK inhibitors.