Hepatosplenic T-cell Lymphoma : Differential
The differential diagnosis of hepatosplenic T-cell lymphoma (HSTCL) includes the following entities:
Aggressive NK/T-cell Lymphoma/Leukemia: Like HSTCL, aggressive NK/T-cell lymphoma/leukemia is a high-grade malignancy with involvement of both liver and spleen and accompanied by B symptoms. Features supporting NK/T-cell lymphoma/leukemia include leukemic component, NK-cell origin, activated cytotoxic phenotype (positivity for granzyme B and perforin), absence of TCR expression, association with EBV, prominent hemophagocytosis, and diffuse/interstitial pattern of bone marrow involvement (in contrast to sinusoidal pattern of HSTCL).
T-cell Large Granular Lymphocytic Leukemia (T-LGLL): T-LGLL is a chronic, indolent lymphoproliferative disorder that is clinically quite distinct from HSTCL. However, the pattern of infiltration of hepatic sinusoids and splenic red pulp by neoplastic cells in T-LGLL may be similar to HSTCL. The features favoring T-LGLL include presentation with a frank leukemic phase; positivity for CD3, CD8, CD57, TCR-alpha-beta phenotype; STAT3 mutations; granzyme B expression; and minimal sinusoidal infiltration of the bone marrow.
Other Gamma-Delta T-cell Lymphomas: Gamma-delta T-cell phenotype is not unique to HSTCL. It can be also seen in some cases of T-cell lymphoblastic lymphomas, T-LGLL, and extranodal cytotoxic T-cell lymphomas.
Hairy Cell Leukemia (HCL): HCL shows peculiar large atypical lymphoid cells with hairy projections on blood smear. The tumor cells are CD25+, CD103+, and CD68+ with a B-cell phenotype.
Splenic Marginal Zone Lymphoma (SMZL): SMZL can show sinusoidal infiltration of bone marrow as well as diffuse involvement of splenic red pulp by small atypical lymphocytes mimicking HSTCL. However, the clinical presentation is indolent and the neoplastic cells have B-cell phenotype.
Other conditions: HSTCL should be differentiated from the benign reactive gamma-delta T-cell expansion in the peripheral blood that is sometimes seen in infectious, inflammatory, or autoimmune diseases.
HSTCL is normally composed of monomorphic, medium-sized lymphoid cells lacking significant pleomorphism. However, the example shown here had scattered areas with greater degree of anaplasia and increased mitotic activity. The diagnosis was confirmed with immunophenotypic studies.