Nonhepatosplenic gammadelta T-cell lymphoma: a subset of cytotoxic lymphomas with mucosal or skin localization.

Human gammadelta 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 postthymic neoplasms that arise from this T-cell subpopulation belong to the hepatosplenic gammadelta lymphoma entity. Only a few cases of nonhepatosplenic gammadelta lymphomas have been described in detail previously. This study presents the clinicopathologic features of 11 consecutive cases of nonhepatosplenic gammadelta lymphoma. All were characterized 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 peripheral 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 receptor (TCR)delta-1+), betaF1- phenotype. They were CD5- (9 of 10) and CD4-/CD8- (9 of 10) or CD8+ (1 of 10). A clonal gamma-chain gene rearrangement was detected in all tested cases (9/9). All cases had an activated cytotoxic T-cell intracellular antigen-1 (TIA-1)+, Granzyme B+ phenotype. Epstein-Barr virus (EBV) sequences were detected in six cases by in situ hybridization (ISH). Despite an aggressive clinical course, complete remission was obtained in three patients, and one of the latter required a peripheral blood stem-cell transplantation. Nonhepatosplenic gammadelta peripheral T-cell lymphoma can be regarded as a model of activated cytotoxic lymphoma, occurring in mucosae or skin. These appear to be derived from the subpopulation of tissue-restricted gammadelta 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.