Increased peripheral blood gamma delta T-cells in patients with lymphoid neoplasia: A diagnostic dilemma in flow cytometry

We have observed increased numbers of non-neoplastic gamma delta-T-cells in the peripheral blood of a series of patients with non-Hodgkin's lymphoma n ot of gamma delta-T-cell origin. The majority of normal gamma delta-T-cells are negative for surface CD4 and CD8 and a subpopulation does not express CD5, two immunophenotypic findings strongly suggestive of neoplasia in alph a beta T-cells. In addition, they express cytotoxic T-cell/Natural killer c ell antigens. In this study, up to 22% of PBLs were CD4 and CD8 negative ga mma delta-T-cells and up to 33% PBLs were CD5 negative gamma delta-T-cells, In addition, as high as 42% of PBLS were gamma delta-T-cells expressing cy totoxic T-cell/Natural killer cell antigens, suggestive of a large granular lymphoproliferative disorder. Failure to recognize that these are normal g amma delta-T-cells could lead to the erroneous diagnosis of peripheral bloo d involvement with a T-cell neoplasm, especially in the setting of a histor y of non-Hodgkin's lymphoma. Cytometry (Comm. Clin. Cytometry) 38:280-285, 1999. Published 1999 Wiley-Liss, Inc.dagger