Hepatosplenic T-cell lymphoma

HEPATOSPLENIC gd T-CELL LYMPHOMA (HTCL) is an uncommon but distinct T-cell lymphoma with a characteristic growth pattern involving the hepatic and splenic red pulp sinuses^{ref1,
ref2,
ref3,
ref4,
ref5,
ref6,
ref7}. Most tumors have a gd T-cell phenotype; tumors arising from aß T-cells are clinically and pathologically similar^ref. Rare cases of HSTCL expressing the aß chain have been reported, but the prognostic relevance is unknown^ref. The majority of patients succumb to their disease, with an overall median survival of 16 months^ref. The gd phenotype has been rarely identified in primary cutaneous T-cell lymphoma and is a marker of poor prognosis (median survival 15 months vs. 166 months in aß subtypes)^ref. Unlike HSTCL, which express TIA1 but are negative for granzyme B and perforin cytotoxic proteins, primary cutaneous gd TCL express all cytotoxic proteins, thus demonstrating an activated T-cell phenotype which may contribute to their aggressive behavior^ref. gd T-cells are normally the first line of defense at epidermal and epithelial surfaces and they represent 10-12% of lymphocytes in the spleen^ref1,
ref2
Epidemiology : most cases occur in young adult males (median age, 29-34 yrs)
Aetiology : approximately 20% arise in immunosuppressed, predominantly posttransplant patients^{ref1,
ref2,
ref3}
Symptoms & signs : B symptoms, splenomegaly (98%), hepatomegaly (80%), no lymphadenopathy, anemia, and severe thrombocytopenia (80-85%).
Laboratory examinations : bone marrow involvement

cytomorphology : the tumor cells are homogeneous, medium-sized lymphocytes with partially dispersed chromatin, inconspicuous nucleoli and generally little cytologic atypia. Circulating tumor cells are present in the blood in 25-50% or more of patients during the course of disease. On Wright's stain the cells have partially condensed chromatin and pale blue cytoplasm. The presence of cytoplasmic granules is variable, but most report the cells are agranular. Marrow involvement is present in approximately 66% of cases but is usually subtle involving the sinuses. Immunoperoxidase staining for T-cell antigens is important to aid in recognition^ref1,
ref2
cytogenetics : HCTL has a recurrent chromosome abnormality, isochromosome 7q, that appears to be the primary genetic event in its pathogenesis^{ref1,
ref2,
ref3,
ref4,
ref5}. Trisomy 8 is a common cytogenetic abnormality
immunophenotype : CD2⁺3⁺4^-5^-7⁺8^{-,
rarely +}16⁺56⁺57^-, TcRgd⁺; HTCL arises from an CD4^- CD8^- T cell or, in 15%, a CD4^- CD8⁺ T-cell. The NK-cell associated antigen CD56 is expressed in 60-70% of cases, so many of these cases have an NK-like T-cell phenotype. TIA-1 is present in virtually all cases, but approximately 50% lack granzyme B and or perforin, indicating a non-activated cytolytic T-cell phenotype.

Therapy : most patients are refractory or have brief responses to anthracycline therapy with death occurring < 1 year after diagnosis^ref1,
ref2.
Differential diagnosis :

large granular lymphocyte (LGL) leukemia which usually occurs in older patients often with a history of rheumatologic disease, is indolent, and most often arises from CD57⁺ rather than CD56⁺ T-cells^ref1,
ref2
aggressive NK-cell leukemia may present with hepatosplenomegaly but morphologically the tumor has a more blastic cytology and expresses all cytolytic proteins whereas hepatosplenic lymphoma usually expresses TIA-1 only and lacks granzyme B and perforin^{ref1,
ref2,
ref3,
ref4,
ref5,
ref6}
CD8⁺ T-cell CLL is a rare disease that has more marrow involvement than hepatosplenic lymphoma and it lacks cytolytic granules and NK-cell associated antigens^ref.

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