NONHEPATOSPLENIC GAMMA-DELTA T-CELL LYMPHOMA - A SUBSET OF CYTOTOXIC LYMPHOMAS WITH MUCOSAL OR SKIN LOCALIZATION

Human gamma delta T lymphocytes represent a minor subset of T cells in the peripheral blood, which exhibit a limited diversity and a tissue- restricted repertoire in contrast to their broad specificity. Most pos tthymic neoplasms that arise from this T-cell subpopulation belong to the hepatosplenic gamma delta lymphoma entity. Only a few cases of non hepatosplenic gamma delta lymphomas have been described in detail prev iously. This study presents the clinicopathologic features of 11 conse cutive cases of nonhepatosplenic gamma delta lymphoma. All were charac terized by mucosal or skin initial involvement: nasal cavity (n = 3), gastrointestinal tract (n = 3), skin (n = 3), lung (n = 1), larynx (n = 1). Most patients presented with B symptoms (eight of 11), without p eripheral lymphadenopathy and bone marrow involvement. A past history of chronic antigen exposure was noted in six cases, and four patients had features of immune deficiency. On histology, they were classified as pleomorphic tumors. Features of epitheliotropism and angiocentrism was observed in most cases. Tumor cells had a CD2(+), CD3(+), T-cell r eceptor (TCR)delta-1(+), beta F1(-) phenotype. They were CD5(-) (9 of 10) and CD4(-)/CD8(-) (9 of 10) or CD8(+) (1 of 10). A clonal gamma-ch ain gene rearrangement was detected in all tested cases (9/9). All cas es had an activated cytotoxic T-cell intracellular antigen-1 (TIA-1)(), Granzyme B+ phenotype. Epstein-Barr virus (EBV) sequences were dete cted in six cases by in situ hybridization (ISH). Despite an aggressiv e clinical course, complete remission was obtained in three patients, and one of the latter required a peripheral blood stem-cell transplant ation. Non-hepatosplenic gamma delta peripheral T-cell lymphoma can be regarded as a model of activated cytotoxic lymphoma, occurring in muc osae or skin. These appear to be derived from the subpopulation of tis sue-restricted gamma delta lymphocytes, which are involved in the host epithelial surface surveillance. The role of chronic antigen exposure in the pathogenesis of these rare lymphomas can be suggested, in view of the past history observed in at least some patients. (C) 1998 by T he American Society of Hematology.