T-immunoblastic lymphoma mimicking B-immunoblastic lymphoma

A T-cell immunoblastic lymphoma having plasmacytoid features that mimic B-cell immunoblastic lymphoma, is described. The lesion was composed of sheets of pleomorphic plasmacytoid cells that displayed a helper T-cell immunophenotype (Leu-1+, Leu-3+, Leu-4+, Leu-5+, Leu-9-, Leu-2-). Ultrastructural features were consistent with a T-cell lymphoma. Flow cytometric analysis revealed that the cells were DNA triploid and had a high proliferative activity. Although the histology of immunoblastic lymphomas alone may suggest either a T- or B-cell phenotype, immunophenotyping is essential in making this distinction.