In MDS and sAML samples, the composition, quantity, and spatial proximity of immune cell subsets to CD34+ blasts were heterogeneous and correlated to the blast counts, but not to the genetics of the diseases, while in non-neoplastic BMB no CD8+ and FOXP3+ T cells and only single MUM1p+ B/plasma cells were detected in a distance of ≤10 μm to CD34+ hematopoietic progenitor cells (HPSC). Here, CD34 is linked to myelodysplastic syndrome.