Hepatosplenic T-cell lymphoma (HSTCL) is a rare, aggressive T-cell lymphoma that can be challenging to diagnose. In particular, distinguishing HSTCL from T-cell large granular lymphocytic (T-LGL) leukemia of γδ T-cell receptor (TCR) type is difficult without examination of a splenectomy specimen. In this study, we systematically assessed a series of HSTCL cases for findings reported in the literature as supporting or not supporting the diagnosis of HSTCL. We also compared HSTCL with a group of cases of T-LGL of γδ TCR type. Criteria assessed in this study included: B-symptoms, massive splenomegaly, lymphadenopathy, extranodal involvement, peripheral lymphocytosis, lymphoma cells that expand bone marrow sinuses, lymphocyte azurophilic granules, immunophenotype, evidence of infection by Epstein-Barr virus, human immunodeficiency virus, or human T-cell leukemia virus type 1, isochromosome 7q, trisomy 8, and TCR gene rearrangement status. On the basis of the data of this study, we conclude that massive splenomegaly, bone marrow sinusoidal expansion by lymphoma cells, and lymphocytes devoid of azurophilic granules were significantly more common in HSTCL patients than in γδ T-LGL patients (P<0.0001), and these features help support the diagnosis of HSTCL.