Atypical Lymphocytes
Overview
The term atypical lymphocyte is used to refer to any abnormal lymphocyte that does not appear reactive. The presence of such cells in the peripheral blood suggests a neoplastic process, such as a lymphoid leukaemia or the leukaemic phase of lymphoma. These cells may be difficult to distinguish on morphological examination.
Causes of Atypical Lymphocytes
- Mature B cell leukaemias - CLL, B cell prolymphocytic leukaemia, hairy cell leukaemia, hairy cell leukaemia variant
- Leukaemic phase of B cell lymphomas - follicular lymphoma, mantle cell lymphoma, splenic marginal zone lymphoma, diffuse large B cell lymphoma, burkitt lymphoma
- Mature T cell neoplasms - T cell prolymphocytic leukaemia, T cell large granular lymphocytic leukaemia, adult T cell leukaemia / lymphoma, Sezary syndrome, anaplastic large cell lymphoma
Interpretation
- Chronic lymphocytic leukaemia - large numbers of small mature lymphocyes with smudge cells
- Hairy cell leukaemia - medium-sized cells with 'hairy' projections
- Follicular lymphoma - small cells with deeply clefted nuclei
- Splenic marginal zone lymphoma - 'polar' projections from two ends of the cell
- Diffuse large B cell lymphoma - large cells with cytoplasmic vacuoles
- Burkitt lymphoma - deeply basophilic cytoplasm with vacuoles
- T large granular lymphocytic leukaemia - medium-sized cells with the nucleus to one side of the cell, and azurophilic granules
- Sezary syndrome - 'cerebriform' nucleus (looks like a brain)
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------