Granular lymphocytic leukemia derived from γδ T-cell expressing cytotoxic molecules

We here present an extremely rare case of granular lymphocytic leukemia derived from γδ T-cell (γδ T-GLL). The blood picture at diagnosis was as follows; white cell count 25.7×10⁹/l containing 94% atypical lymphocytes with cytoplasmic granules, hemoglobin 11.8 g/dl and platelet count 124×10⁹/l. The atypical lymphocytes were positive for CD2, CD3, CD5, CD7, CD56 and TCR γδ, but negative for CD4, CD8, CD57, TCR αβ and B-cell antigens. The cytotoxic molecules, T-cell intracellular antigen-1 (TIA-1) and granzyme B, were positive by immunocytochemical analysis. Southern blot analysis showed rearrangement of T-cell receptor Jγ and Cβ genes but germline configuration of the JH gene. Neither serum antibody against human T-cell leukemia virus type-I (HTLV-I) nor the integration of HTLV-I proviral DNA was detected. CT scan showed splenomegaly but no lymph node enlargement. A diagnosis of γδ T-GLL was made, and she has been followed up without any therapies for more than 4 years.