[Large granular lymphocytic leukemia CD3^-CD56^-: a challenge for the biologist and the physician]

Large granular lymphocyte leukemia (LGL) are chronic lymphoproliferative disorders classified into three main groups: T-cell LGL leukemia (T-LGL), aggressive NK-cell leukemia and chronic lymphoproliferative disorder of NK cells (NK-LGL). Patients with LGL leukemia exhibit chronic (>3 months) and moderate (<1G/L) to substantial monoclonal expansion of large granular lymphocytes in the peripheral blood. Cytologically, large granular lymphocytes are medium to large cells which are further characterized by an eccentric nucleus and a slightly basophilic cytoplasm containing azurophilic granules. Typically, T-LGL (CD3-and mostly CD8⁺) can be differentiated from NK-LGL disorders (CD3-) based on flow cytometry analysis. However, distinction between LGL leukemias can be tricky. We report here the case of a 47-year-old woman patient diagnosed with large granular lymphocytes leukemia associated with atypical CD3-CD56- immunophenotyping and clinical manifestations of pseudo-Felty's syndrome.