The patterns and diagnostic significance of the lack of surface immunoglobulin light chain on mature B cells in clinical samples for lymphoma workup.

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Cytometry. Part B, Clinical cytometry


BACKGROUND: Surface immunoglobulin (sIg) light chains are not always detected on mature B cells. This may present as a challenge for clonality determination in clinical flow cytometry.

METHODS: To explore the mechanism and diagnostic significance of sIg negative mature B cells, we retrospectively studied 14 cases of sIg negative reactive B-cell lymphocytosis and 89 cases of sIg negative mature B-cell lymphomas. The expression patterns of sIg and cytoplasmic immunoglobulin (cIg) light chains were studied by flow cytometry using both monoclonal and polyclonal antibodies.

RESULTS: These 14 cases of sIg negative reactive B-cell lymphocytosis were proven to be polytypic based on cytoplasmic light chain studies. In 89 cases of sIg negative mature B-cell lymphomas, we described four distinct patterns of abnormal light chain expression including partial or complete loss of sIg or cIg, suggesting different underlying mechanisms.

CONCLUSIONS: This study represents the first reported series of body or cystic fluids where reactive B cells do not have detectable sIg, arguing strongly against making a diagnosis of B-cell lymphoma based on lack of sIg in mature B cells. Since the lack of sIg does not always predict clonal/neoplastic mature B-cell proliferation, further cIg evaluation should be performed when sIg expression is not detected in mature B cells. The lack of both sIg and cIg in mature B cells may serve as a reliable surrogate clonality/neoplastic marker.


Online ahead of print.





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