Frequency and Relevance of CD10+CD19+Hematogones after Allogeneic Stem Cell Transplantation.

Hematogones are B-lymphocyte precursors found in large frequencies after chemotherapies. In this study, the frequency of CD10+CD19+ hematogones was analysed routinely prior and post allogeneic stem cell transplantation and compared with moelculargenetic data for donor chimerism and for clonal translocations. Because of similarities in morphology and immunophenotype with frequent expression of CD19, CD10 and TdT they may undistinguishable from malignant B-cell lymphoblasts. As one example underlying the diagnostic difficulties, one patient with thrombopenia day +60 after allogeneic stem cell transplantation is presented. A relapse of Richter's syndrome was suspected. Investigations of bone marrow specimens revealed a mixed chimerism, the frequency of cells coexpressing CD10 and CD19 was 28%. However, a CD19-sorted chimerism revealed an almost complete donor chimerism. Donor-lymphocytes were administered to improve graft function. Afterwards, donor chimerism reached 100% and platelets reached normal values, but hematogones continued to exceed 5% in the following specimens. As a result of such cases, bone marrow specimens after allogeneic stem cell transplantation were systematically analyzed for the presence of hematogones.