Histiocytic sarcoma of the central nervous system: a challenging diagnosis

A 43-year-old woman was admitted in our department for progressive ataxia, headache and altered general status lasting for 3 weeks. Brain magnetic resonance imaging (MRI) showed multifocal lesions in hypersignal T2 and with homogeneous gadolinium enhancement in T1 sequences (Figure 1). Extensive cerebrospinal fluid (CSF) examination with isoelectric focusing, search for malignant or lymphomatous cells, microbacterial analysis, including China ink and mycobacterium cultures and polymerase chain reaction (PCR), trophyrema whippeli PCR was normal. Thorax and abdomen computerized tomography (CT) scan, bone scintigraphy, whole body positron emission tomography (PET) fluorodesoxyglucose (FDG) scan, bones X-rays and bone marrow biopsy did not show any abnormality. ... Therefore, a stereotactic biopsy of the periventricular lesion was performed. Microscopically, the lesion was composed of histiocyte cells with a pale cytoplasm, cytonuclear inequalities and atypical nuclei associated with intense glial reaction and moderate polymorphic inflammatory infiltration (Figure 2). There were no foam cells nor necrosis. Mitoses were observed. Immunohistochemical stainings were positive for CD68, CD163, CD14 and S-100, but negative for CD1a, CD45, CD3, CD20, CD15, CD30 and CD56. A diagnosis of histiocytic sarcoma was made. Despite several lines of chemotherapy (steroid treatment, vinblastine, cladribine), evolution was fatal within 10 months.