Small cell variant of T-cell prolymphocytic leukemia with a gammadelta 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 alphabeta phenotype. 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 gammadelta antigens and negative for CD1a, CD4, and TCR alphabeta antigens. Southern blot analysis revealed rearrangement of the TCR Jgamma and Jdelta-1 genes. A cytogenetic study of peripheral blood showed a normal karyotype. T-PLL with a TCR gammadelta phenotype 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 gamma8 type of T-PLL will become clearer.