Small Cell Variant of T-Cell Prolymphocytic Leukemia with a γδ Immunophenotype

T-cell prolymphocytic leukemia (T-PLL) is a rare postthymic T-cell disorder. The disease is characterized by lymphadenopathy, splenomegaly, skin lesions, a high white blood cell count, and an aggressive clinical course. The small cell variant of T-PLL occurs in approximately 20% of patients. Most T-PLL patients express membrane T-cell receptors (TCR) of the γ βphenotype. The diagnosis of small cell variant T-PLL in a 56-year-old woman was based on the findings of abnormal lymphocytosis, immunophenotype, lymphadenopathy, and aggressive clinical behavior. Immunophenotype analysis showed that lymphocytes were positive for CD2, CD3, CD5, CD7, CD8, and TCR γ δ antigens and negative for CD1a, CD4, and TCR α β antigens. Southern blot analysis revealed rearrangement of the TCR Jγ and Jδ-1 genes. A cytogenetic study of peripheral blood showed a normal karyotype. T-PLL with a TCR α βphenotype is very rare. This case was typical T-PLL except for the morphologically small cell type and the lack of the typical chromosome aberration. If cases accumulate in the future, the specific features of the γ δ type of T-PLL will become clearer.