Disseminated histiocytoses: Biomarkers beyond BRAFV600E.
e22207 Background: Histiocytoses are rare tumors characterized by the primary accumulation of monocytes, macrophages and dendritic cells. The most frequent subtypes are Rosai-Dorfman disease (RDD), Langerhans cell histiocytosis (LCH), Erdheim-Chester disease (ECD) and follicular dendritic cell sarcomas (FDCS). Clinical presentations range from localized to disseminated, life threatening disease. Identification of an activating BRAFV600E mutation in the majority of ECD and LCH cases provided the basis for the use of BRAF and MEK inhibitors in these patients. Responses have been reported with BRAF inhibitors, but no curative treatment has yet been developed. Thus, additional targeted therapies are needed. Methods: Twenty-two cases (M:F = 13:9, age range 2-65 years) of histiocytic diseases (4 RDD, 10 LCH, 4 ECD, 2 FDCS, 1 histiocytic sarcoma [HS] and 1 blastic plasmacytoid dendritic cell neoplasm [BPDCN]) were analyzed using immunohistochemical and molecular methods (cobas 4800 BRAFV600 Mutation Test and The...