Hepatosplenic Tcell Lymphoma

General: Hepatosplenic T-cell lymphoma (HSTL) is a rare systemic lymphoma that generally presents with involvement of the liver, spleen, and bone marrow.109 Initially described as a lymphoma of 78-type T-cells, it is now known that some otherwise identical cases consist of ap T-cells. Importantly, it should be realized that other types of T-cell lymphoma may consist of 78-type T-cells and such cases should not be categorized as HSTL solely because of the type of T-cell receptor expressed.

Pathology: There is typically splenomegaly, and his-tologic sections of the spleen display prominent red pulp infiltration by a proliferation of intermediate-sized lymphoid cells. The white pulp is characteristically uninvolved.109110 Similarly, the liver displays a striking infiltrate of the hepatic sinusoids by similar appearing cells, with sparing of the portal tracts. The bone marrow is also usually involved, and displays clusters of intermediate-sized lymphoid cells within the sinusoids.110'111

Immunophenotype: Typical cases display an immature cytotoxic T-cell phenotype with expression of TIA1, but not perforin or granzyme B. Most cases are positive for CD2 and CD3, but are negative for CD4, CD5, and CD8.109110 Expression of other T-cell associated antigens is variable. Most cases express the 78 T-cell receptor, although occasional ap T-cell receptor positive cases are well described.109,112 Many cases show co-expression of CD56. There is no association with EBV.

Molecular genetics: Many cases appear to be associated with a recurrent cytogenetic abnormality, isochromosome 7q.109,110 The exact incidence of i(7q) in HSTL has not yet been clarified, although it is clear that not all cases contain this abnormality. Monoclonal T-cell receptor rearrangements may be detected by PCR or Southern blot studies.

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