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Clinical significance of monoclonal B cells in cerebrospinal fluid
Grzegorz S Nowakowski1, Timothy G Call, William G Morice
1Division of Hematology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA. nowakowski.grzegorz@mayo.edu
Insights
Detecting monoclonal B cells in cerebrospinal fluid (CSF) via flow cytometry may not indicate central nervous system (CNS) malignancy in patients with indolent B-cell disorders. Further clinical evaluation is crucial for accurate diagnosis.
Area of Science:
- Neuroscience
- Hematology
- Immunology
Background:
- Morphologically malignant lymphocytes in cerebrospinal fluid (CSF) suggest central nervous system (CNS) lymphoid malignancy.
- Flow cytometry detects monoclonal B-cells in CSF, but its significance without morphologically malignant cells is unclear.
Purpose of the Study:
- To investigate the clinical significance of detecting monoclonal B-cells in CSF using flow cytometry.
- To determine if monoclonal B-cells in CSF, without morphologically malignant cells, indicate CNS involvement in lymphoid malignancy.
Main Methods:
- Retrospective review of 32 patients' CSF flow cytometry results over 5 years.
- Identification of patients with monoclonal B-cells in CSF.
- Review of clinical presentation and course for these patients.
Main Results:
- Twelve patients had monoclonal B-cells in CSF; only three showed clinical evidence of CNS malignancy.
- Nine patients without clinical CNS malignancy had nonmalignant neurologic disease or indolent lymphoproliferative disorders (chronic lymphocytic leukemia, mantle cell lymphoma).
- Monoclonal B-cells in patients with chronic lymphocytic leukemia and mantle cell lymphoma were small and immunophenotypically similar to circulating malignant cells; none developed CNS involvement.
Conclusions:
- The presence of monoclonal B-cells in CSF may not always signify clinically significant CNS involvement in indolent B-cell malignancies.
- Careful clinical correlation is necessary when interpreting CSF flow cytometry findings for lymphoid malignancy.
Background:
Morphologically malignant lymphocytes in the cerebrospinal fluid (CSF) are highly suggestive of central nervous system involvement by lymphoid malignancy. Although flow cytometry is increasingly used to detect a monoclonal B-cell population in the CSF, the significance of this finding in the absence of morphologically identifiable malignant cells is unknown.
Methods:
We reviewed CSF flow cytometric results in 32 patients studied at a single institution over 5 years and identified patients who had monoclonal B-cells in the CSF. Clinical presentation and course were reviewed.
Results:
Twelve patients had a monoclonal B-cell population in the CSF, but only three had clinical evidence of malignant CNS disease. Of the other nine patients, 4 had nonmalignant neurologic disease and five had a lymphoproliferative disorder: chronic lymphocytic leukemia (n = 4) and mantle cell lymphoma (n = 1). In patients who had chronic lymphocytic leukemia and mantle cell lymphoma, the monoclonal B-cell population was small and had an immunophenotype identical to that of circulating malignant B cells. None of these nine patients developed clinical evidence of malignant CNS involvement during follow-up.
Conclusion:
In patients who have indolent B-cell malignancies, the presence of monoclonal B cells in the CSF may not be diagnostic of clinically significant CNS involvement by a lymphoid malignancy.
