Hepatosplenic T-cell lymphoma: an unusual case of a gamma delta T-cell lymphoma with a blast-like terminal transformation.

We describe a case of a middle-aged women who presented with anemia and mild hepatosplenomegaly and who was found to have an unusual peripheral T-cell lymphoma with only subtle morphologically abnormal but mature-appearing cells noted in the blood and bone marrow. Less than 2 years after diagnosis the patient presented with an increasing white blood cell count to 26 x 10(9)/L, and numerous blasts were noted in the periphery. Flow cytometry studies showed cells with an unusual T-cell phenotype expressing the gamma delta T-cell receptor and restricted expression of the V delta 1 but not the V delta 2 protein, indicating the clonal nature of the proliferation. A clonal T-cell receptor gene rearrangement was seen with a V delta 1 probe. The patient died and was found at autopsy to have extensive hepatic sinusoidal infiltration by abnormal cells. The histopathologic, immunophenotypic, and molecular findings are those of "hepatosplenic T-cell lymphoma." In spite of the striking morphologic change during the course of the patient's disease the same phenotype and clonal rearrangement were found both at initial diagnosis and during terminal phase, indicating that this change represented a blast-like transformation of the patient's original lymphoproliferative disorder.