Small-Sized Clone of T Cells in Multiple Myeloma Patient after Auto-SCT: T-LGL Leukemia Type or Clonal T-Cell Aberration?

Second cancers and particularly postransplant lymphoproliferative disorders (PTLDs) are extremely rare in patients undergoing autologous peripheral blood stem cell transplantation (auto-SCT). We report the case of clonally rearranged T-cell expansion which occurred after auto-SCT for Multiple Myeloma (MM). Does asymptomatic clonal T-cell large granular lymphocytic proliferation, in our experience, represent either a secondary cancer after auto-SCT or clonal T cell aberration or derive from expansion of coexisting undetected small-sized clone of T cells? 1. Introduction PTLDs were initially recognized in solid organ transplant recipients, and their incidence can range from 1% to 6%. Among patients undergoing haematopoietic cell transplantation, PTLDs occur almost exclusively in recipients of allogeneic grafts (allo-SCT) with an overall incidence rate from 1% to 2% and manifest early within the first year from transplantation [1–3]. Second cancers and particularly PTLDs are extremely rare in patients undergoing auto-SCT [4–7]; according to Fenk et al., the median time from diagnosis of MM to the occurrence of secondary malignancies is 56 months [7]. The majority of PTLDs are of B-cell origin but they may also originate from T cells [8], but very rarely from natural killer cells [9]. We report the case of clonally rearranged T-cell expansion mimicking T-cell large granular lymphocytic (T-LGL) leukemia which occurred after auto-SCT for MM. The diagnosis of T-LGL leukemia requires a multiparametric approach including peripheral blood examination, bone marrow aspirate and bone marrow trephine biopsy with immunohistochemistry, flow cytometric immunophenotyping, and molecular analysis for TCR gene rearrangements. According to the World Health Organization classification of lymphoid neoplasms, T-LGL leukemia is characterized by a persistent (>3 months) increase of large granular lymphocyte (2 × 109/L); cases with an LGL count of <2 × 109/L can be diagnosed as T-LGL leukemia only if clonal rearrangement of T-cell receptor (TCR) gene is demonstrated. T-LGL leukemia is distinguished from reactive polyclonal granular lymphocytes through both the aberrant coexpression of the natural killer cell-associated antigen CD57 and demonstration of T-cell clonality. 2. Case Report A 70-year-old male patient, undergoing a first auto-SCT for stage IIIA MM IgAλ, manifested early an asymptomatic clinically lymphoproliferative disorder similar to T-LGL leukemia. He had been conditioned with melphalan 140？mg/m2 after induction therapy with VTD regimen (Bortezomib 1,3？mg/m2 on days