Introduction: Two forms of growth are reported in the neuroradiology of cerebral lymphomas: mass, single or multiple lesions, with homogeneous contrast enhancement, and diffuse infiltration. Flow cytometry enables us to diagnose non-Hodgkin's lymphoma, when clonality of B cells is detected. It is usually employed with peripheral blood or bone marrow samples but can be used with cerebrospinal fluid (CSF).
Case report: We report the case of a 68-year-old female, who was admitted to hospital because of rapidly progressive onset of confusion and right-side hemiparesis that developed in a matter of days. Magnetic resonance imaging (MRI) of the head showed a diffuse infiltrative lesion, without contrast enhancement, which covered the left basal nuclei, the left frontal white matter, the genu of the corpus callosum and the right frontal white matter. The CSF showed slight pleocytosis (20 cells/mL) and a notable degree of hypoglycorrhachia (10 mg/dL). The cytological examination only revealed lymphocytes, with no data indicating atypicality. The flow cytometry assay detected large mononuclear B cells, with the CD19 + CD20 + CD10-lambda phenotype, which is characteristic of diffuse non-Hodgkin's lymphoma of large B cells. The clinical course ran quickly towards a fatal outcome; it progressed to left-side hemiplegia and coma, and the patient died two weeks after admission to hospital.
Conclusions: In cases of cerebral lymphoma, especially when the neuroradiological pattern displays diffuse infiltration and there are anomalies involving CSF, the flow cytometry in CSF can be diagnostic, thus avoiding the need for other invasive brain procedures to deal with lesions that are usually located deep inside the brain at badly defined sites.