[Diagnostic value of brain biopsy in intravascular large B-cell lymphoma mimicking progressive multifocal leukoencephalopathy: case report].

: We report a 68-years-old woman with systemic sclerosis and interstitial pneumonia (IP). She had developed subacute progressively encephalopathy and dementia while treated with oral cyclophosphamide and prednisolone. She admitted to our hospital because of syncope. Laboratory tests indicated slight elevated cerebrospinal fluid protein, and levels of serum C-reactive protein (CRP), levels of soluble IL-2 receptor was normal. But, magnetic resonance imaging (MRI) of the brain showed multiple infarct-like lesions mainly in the white matter, which mimics progressive multiple leukoencephalopathy (PML). Twenty days after admission, the retested MRI of the brain disclosed initial lesions progressively enlarged and numbers of the lesions were increased. The polymerase chain reaction (PCR) for JC virus of cerebrospinal fluid was negative. To make diagnosis, brain biopsy was performed. Microscopic examination revealed that small vessels were filled with lymphoma cells (CD20+, CD79+, CD3-), and intravascular lymphoma (IVL) was diagnosed. She treated with regimens of R-CHOP. After chemotherapy her consciousness and dementia were gradually improved. IVL of central nerve system (CNS) is a rare disease, and its common symptoms are ischemia, infarction and dementia. Diagnosis of IVL of CNS is difficult when the lesion mimics PML, and patient with similar laboratory examinations and radiographic findings of PML should undergo brain biopsy detected malignant cell in small vessels, which is a value of diagnosis.