The present invention relates to the field of diagnosis and therapy of hematological malignancies based on the tumor antigen FMR1NB (also called NY-SAR-35, Cancer/testis antigen 37 or Fragile X mental retardation 1 neighbor protein) and agents specifically targeting this antigen or cells expressing the same, e.g., antibodies. The inventors were able to prove that the molecule is expressed on the cell surface and thus represents a particularly advantageous target in cancer therapy and vaccination. Surprisingly, FMR1NB was found to be associated with hematological malignancies, e.g. acute myeloid leukemia (AML) or chronic myeloid leukemia (CML).