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Cerebrospinal fluid pleocytosis in aseptic meningitis: cytomorphic and immunocytochemical features
J S Ross1, C Magro, W Szyfelbein
1James Homer Wright Pathology Laboratories, Massachusetts General Hospital, Boston.
Abstract:
We report five cases of aseptic meningitis presenting with high cerebrospinal fluid (CSF) cell counts (260-600 cells/cmm) and mononuclear pleocytosis, suggesting the diagnosis of CNS malignant lymphoma. In four of five cases a reactive background of small lymphocytes, monocytes, and eosinophils was seen. Immunocytochemical studies in all five cases revealed that 100% of the lymphoid cells were T-cells. Three of four cases evaluated for lymphocyte subsets displayed a CD4 to CD8 ratio of 3:1. In the fourth case the CD4:CD8 was 1 to greater than 10; this patient was subsequently proven to have AIDS with HIV meningitis. In this study the cytologic features of the benign atypical lymphoid pleocytosis of aseptic meningitis in contrast to malignant lymphomas in CSF specimens included small or indistinct nucleolus, regular perinucleolar area, smaller widely separated chromatin aggregates, generally ample cytoplasm with perinuclear clearing and polyclonal T-cell immunophenotype.
Insights
Aseptic meningitis can mimic CNS lymphoma with high CSF cell counts. Cytologic analysis reveals benign T-cells, distinguishing it from malignant lymphoma and aiding diagnosis.
Area of Science:
- Neurology
- Cytopathology
- Immunology
Background:
- Aseptic meningitis can present with high cerebrospinal fluid (CSF) cell counts and mononuclear pleocytosis.
- These findings can be mistaken for central nervous system (CNS) malignant lymphoma.
Purpose of the Study:
- To differentiate aseptic meningitis from CNS malignant lymphoma based on CSF cytologic features.
- To investigate the immunophenotype of lymphoid cells in aseptic meningitis.
Main Methods:
- Analysis of CSF cytology from five cases of aseptic meningitis.
- Immunocytochemical studies to determine lymphoid cell lineage and subsets.
- Comparison of cytologic features with known CNS lymphoma characteristics.
Main Results:
- All five cases showed 100% T-cells in CSF.
- Four cases exhibited a reactive background of lymphocytes, monocytes, and eosinophils.
- Cytologic features included small nucleoli, regular perinucleolar areas, dispersed chromatin, ample cytoplasm, and polyclonal T-cell immunophenotype, differentiating from lymphoma.
Conclusions:
- Cytologic examination of CSF, including immunophenotyping, is crucial for distinguishing aseptic meningitis from CNS lymphoma.
- Aseptic meningitis typically shows benign, polyclonal T-cell pleocytosis with specific cytologic features.
- One case with an atypical CD4:CD8 ratio was associated with acquired immunodeficiency syndrome (AIDS) and HIV meningitis.