Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 15 4 2021 10 14 260 262 EN Yi Li Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, United States Emily Sloan Department of Pathology, University of California San Francisco, San Francisco, California, United States Andrew Bollen Department of Pathology, University of California San Francisco, San Francisco, California, United States. David Solomon Department of Pathology, University of California San Francisco, San Francisco, California, United States Philip Theodosopoulos Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States Soonmee Cha Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, United States 2020 06 01 2020 12 13 Rosai Dorfman disease is a rare histiocytic disorder of over-production of non-Langerhans histiocytes, which typically manifests with massive lymphadenopathy and sinonasal involvement.  We report a rare case of systemic and disseminated craniospinal Rosai-Dorfman disease with intraparenchymal and leptomeningeal involvement, but no sinus or dural-based disease.  The diagnosis was established by biopsy of a hypothalamic mass.  Additionally, UCSF500 Next Generation Sequencing demonstrated a solitary pathogenic alteration affecting the BRAF oncogene, which supports the morphologic and immunohistochemical diagnosis of Rosai-Dorfman disease. https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/1356 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/1356/893