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This is a 15-year-old male with anemia and hepatosplenomegaly with evidence of HbC disease. A bone marrow biopsy was performed to assess for the cause of cytopenias. Shown here are images from the marrow biopsy H&E and three immunostains.
(A) H&E stain: In the central areas, a vague luminal structure consistent with marrow sinuses filled with smaller dark cells which are atypical lymphocytes consistent with neoplastic lymphoid cells. (B) CD3 stain: Immunostain shows multiple clusters of CD3 positive T-cells are present in the biopsy which is abnormal. The CD3 positive T-cells do not express TCRB. (C) TCR-delta immunostain: resembles the pattern of CD3 with sinusoidal T-cells expressing TCR-delta. (D) Distribution of TCRB+ cells does not resemble the pattern of CD3 and TCR-delta IHC indicating that the sinusoidal cells are not alpha-beta T-cells.
There are two types of T-cell receptors: Alpha Beta and Gamma Delta. Most normal T-cells express TCR-alpha/beta on the surface. Only a very small subset express GD TCR. Alpha Beta T-cell receptors are involved with the control of intracellular bacterial infection and have many V genes.
Gamma Delta T-cell receptors are found in low abundance in the gut mucosa, skin, lungs, and uterus. Unlike Alpha Beta T-cell receptors, the function and specificity are largely unknown of Gamma Delta T-cell receptors.
This case illustrates a lymphoma arising from Gamma-delta T-cells. The characteristic sinusoidal pattern seen here is typical of HSTL involving the marrow. However, no 7q aberration commonly noted in HSTL present by FISH testing in this case.