title: Primary histiocytic sarcoma of the central nervous system.
abstract: Histiocytic sarcoma is a type of lymphoma that rarely involves the central nervous system (CNS). Its rarity can easily lead to a misdiagnosis. We describe a patient with primary CNS histocytic sarcoma involving the cerebral hemisphere and spinal cord, who had been initially misdiagnosed as demyelinating disease. Two biopsies were necessary before a correct diagnosis was made. A histologic examination showed bizarre shaped histiocytes with larger nuclei and nuclear atypia. The cells were positive for CD68, CD163, and S-100 protein. As a resection was not feasible due to multifocality, he was treated with highdose methotrexate, but showed no response. As a result, he was switched to high dose cytarabine; but again, showed no response. The patient died 2 months from the start of chemotherapy and 8 months from the onset of symptoms. Since few patients with this condition have been described and histopathology is difficult to diagnose, suspicion of the disease is essential.
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Hoonsub
authors.initials: H
authors.lastname: So
authors.affiliation: Department of Pathology Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Sun A
authors.initials: SA
authors.lastname: Kim
authors.affiliation: Department of Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Dok Hyun
authors.initials: DH
authors.lastname: Yoon
authors.affiliation: Department of Pathology Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Shin Kwang
authors.initials: SK
authors.lastname: Khang
authors.affiliation: Departmens of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jihye
authors.initials: J
authors.lastname: Hwang
authors.affiliation: Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Chong Hyun
authors.initials: CH
authors.lastname: Suh
authors.affiliation: Department of Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Cheolwon
authors.initials: C
authors.lastname: Suh
keywords: Central nervous system; Cytarabine; Histiocytic sarcoma; Methotrexate