Hepatosplenic T-cell lymphoma

Hepatosplenic T-cell lymphoma is a rare and generally incurable form of lymphoma.

Synonyms
Hepatosplenic γδ T-cell lymphoma

ICD-O Code
9716/3

Definition
Hepatosplenic T-cell lymphoma is a systemic neoplasm comprising medium-sized cytotoxic T-cells that show a significant sinusoidal infiltration in the liver, spleen, and bone marrow.

Epidemiology
This lymphoma is rare, comprising less than 5% of all cases, and is most common in young adults and adolescents. A distinct male gender preference has been described.

Etiology
The cell of origin for this disease is an immature cytotoxic T-cell clonally expressing the γδ T-cell receptor. This disease is seen more often in immunosuppressed solid organ transplant recipients, an association that has led to the hypothesis that long-term immune stimulation in the setting of immunosuppression is the causative agent.

Clinical Presentation
The typical clinical finding in a patient with hepatosplenic T-cell lymphoma is hepatosplenomegaly.

Laboratory Findings
The constellation of thrombocytopenia, anemia, and leukocytosis is common in patients with hepatosplenic T-cell lymphoma. The discovery of neoplastic cells in peripheral blood is often a finding late in the clinical course.

Sites of Involvement
The spleen and liver are always involved, with bone marrow involvement frequently present. Nodal involvement is exceedingly rare.

Morphology
The neoplastic cells in this disorder show a monotonous appearance, with a small amount of cytoplasm and inconspicuous nucleoli.

Spleen and liver
This disease shows a distinct sinusoidal pattern of infiltration which spares the splenic white pulp and hepatic portal triads.

Bone marrow
While the bone marrow is commonly involved, the detection of the neoplastic infiltrate may be difficult due to diffuse, interstitial pattern. Immunohistochemistry can aid in the detection of this lymphoma.

Peripheral blood
Cells of a similar morphology observed in solid organs are observed in peripheral blood.

Immunophenotype
The immunophenotype for hepatosplenic T-cell lymphoma is a post-thymic, immature T-cell.

Genetic findings
Clonal rearrangement of the γ gene of the T-cell receptor is the hallmark of this disease. A few cases have shown rearrangement of the T-cell receptor β gene. Isochromosome 7q has been observed in all cases described so far, sometimes in conjunction with other chromosomal abnormalities such as trisomy 8.

Treatment
CHOP-R frequently induces remission initially, but most patients relapse and die within 2 years. Autologus bone marrow transplantion is currently being investigated in the treatment of hepatosplenic lymphoma.