Application of rearrangements of T cell receptor gene in the diagnosis of mediastinal T-lymphoblastic lymphoma: a case report.

The cytologic diagnosis of lymphoid cells in pleural effusion is not readily apparent. The atypical lymphocytes in reactive process or viral infection may mimic immature lymphoblasts in lymphoblastic lymphoma. Therefore, an objective and reliable method to identify malignant lymphoid cells is important. Here we reported the application of T cell receptor (TCR) gene analysis, together with cytomorphology and immunophenotypic studies, to establish the diagnosis of T-lymphoblastic lymphoma in a 20-year-old female who presented with a mediastinal tumor and pleural effusion. The diagnosis of malignant lymphoma was suspected by cytology and then confirmed by TCR beta chain (TCR beta) gene rearrangement. The rearrangement of TCR beta gene revealed by Southern blot technique implied a T-monoclonal lymphoid population which is most likely malignant. Immunophenotypic studies revealed expression of TdT and T cell antigens indicating a T lymphoblastic lymphoma. As shown in this case, antigen receptor gene analysis can be conducted with a much smaller number of cells to identify a malignant clone among a heterogeneous cell population.