Progression of a myelodysplastic syndrome to pre-B acute lymphoblastic leukaemia with unusual phenotype

This study shows the progression of a myelodysplastic syndrome (MDS) to pre-B acute lymphoblastic leukaemia (ALL) with an unusual phenotype. On diagnosis of leukaemia bone-marrow mononuclear cells were labelled with murine monoclonal antibodies HLA-DR, VIL-A1 (CALLA), 3813, VIM-D5 and with a rabbit antiserum to TdT using a double colour indirect immunofluorescence technique. In addition simultaneous detection of cytoplasmic μ chains (Cyμ) and of TdT was carried out and a direct immunofluorescence analysis for surface membrane immunoglobulins (SmIg) was performed. Two main populations were present: the major one being HLA-DR⁺, Cyμ⁺, VIM-D5⁺, TdT^-, CALLA^-, SmIg^-; the minor one HLA-DR⁺, Cyμ⁺, VIM-D5^-, TdT⁺, CALLA^-, SmIg^-. The progression of our case to acute leukaemia with a population of leukaemic cells each of which demonstrated features of lymphoid and myeloid cells suggests that MDS would originate at the pluripotential stem cell level.