HEPATOSPLENIC T-CELL LYMPHOMA - A DISTINCT CLINICOPATHOLOGICAL ENTITYOF CYTOTOXIC GAMMA-DELTA T-CELL ORIGIN

We identified eight cases of T-cell lymphoma with evidence of a gamma delta phenotype over a 13-year period. Seven of these cases conformed to a distinct clinicopathologic entity of hepatosplenic gamma delta T- cell lymphoma. Nearly all of these patients were young adult males (fi ve of seven), with a median age at presentation of 20 years. They pres ented with marked hepatosplenomegaly, without lymphadenopathy or signi ficant peripheral blood lymphocytosis. Thrombocytopenia was seen in al l patients, and five of seven were mildly anemic. The clinical course was aggressive, and despite multiagent chemotherapy, the median surviv al duration was less than 1 year. The morphologic findings were unifor m; a monomorphic population of medium-sized lymphoid cells with modera tely clumped chromatin and a rim of pale cytoplasm infiltrated the sin usoids of the spleen, liver, and bone marrow. The cells had a characte ristic immunophenotype: CD2(+), CD3(+), CD4(-), CD5(-), CD7(+), CD16(), CD57(-), CD25(-), T-cell receptor (TCR)delta(+), beta F1(-). CD8 wa s positive in four of seven cases tested, and CD56 was positive in fiv e of six. All cases expressed the cytotoxic granule-associated protein , TlA1, but perforin was detected in only one case. All cases with ass essable DNA had a TCR gamma gene rearrangement, and lacked Epstein-Bar r virus sequences. Isochromosome 7q was identified in two cases with c ytogenetic information. The one case of cutaneous gamma delta T-cell l ymphoma differed in its clinical manifestations, histologic appearance , and immunophenotype. We conclude that hepatosplenic gamma delta T-ce ll lymphoma is a distinct clinicopathologic entity derived from cytoto xic gamma delta T cells, and should be distinguished from other lympho mas of T-cell and natural-killer cell (NK)-like T-cell derivation. Thi s is a US government work. There are no restrictions on its use.