Decitabine-containing G-CSF priming regimen overcomes resistance of primary mediastinal neoplasm from early T-cell precursors to conventional chemotherapy: a case report

Abstract

Early T-cell precursor (ETP) leukemia represents a new subtype of T-lymphoblastic leukemia/lymphoma with unique immunophenotypes expressing T-cell and one or more of the myeloid/stem cell markers. Here, we report a young patient who had primary mediastinal mass and pleural effusion without bone marrow involvement. A CT-guided mediastinal biopsy and flow cytometry analysis of the pleural effusion revealed the blast cells to have complicated immunophenotypes: strongly expressed T-cell antigen CD7, myeloid-lineage antigens CD33 and CD13 and stem cell markers cTdT, CD34, and HLA-DR; dimly expressed myeloid-lineage specific antigen cMPO and B-cell antigen cCD79a; but did not express T-cell specific antigen cytoplasmic CD3 and B-cell specific antigen CD19. Clonal T-cell receptor rearrangement eventually determined the cell of origin from ETPs, not myeloblasts. The patient showed primary resistance to lymphoid and myeloid-directed induction therapy. Finally, low-dose decitabine combined with modified-CAG regimen induced a complete remission and allogeneic stem cell transplantation was performed as consolidation. The case indicates a primary mediastinal neoplasm from ETP with distinctive immunophenotype from leukemia type. Low-dose decitabine and modified-CAG regimen in combination with allogeneic stem cell transplantation may improve the outcome of patient.

Keywords: G-CSF priming; T-lymphoblastic lymphoma; decitabine; early T-cell precursor.

Figure 1

The immunohistochemical staining of the mediastinum mass (magnification, ×200). (A) H&E staining. The neoplasm expressed TdT (B), CD7 (C), MPO (E), Ki67 (80%) (F), CD34 (G), CD33 (H), and LCA (I), while it did not express cCD3 (D), CD8 (J), PAX5 (K), and CD1a (L).

Figure 2

The PET-CT imaging of the lesions before and after treatment. In comparison with before treatment (A, B, E, F), the masses disappeared in left cervix, mediastinum, and peritoneal cavity after the completion of therapy (C, D, G, H).

Figure 3

Flow cytometry analysis of lineage antigens of blast cells in pleural effusion. The blast cells brightly expressed CD7, CD33, CD13, cTdT, CD34, HLA-DR, and CD38, dimly expressed cCD79a, cMPO, and CD123, but did not express cCD3, CD19, CD20, CD117, CD2, CD5, CD8, CD10, CD15, CD16, and CD56.

Figure 4

Conal T-cell receptor (TCR) rearrangement of blast cells. Clonal gene rearrangement was observed in TCR beta VJII (A) and TCR delta VD/DD/DJ (B) fragments. In panel (A), the arrow indicates the monoclonal peak of TCR beta VJII. In Panel (B), the arrow indicates the monoclonal peak of TCR delta VD/DD/DJ.