The absence of a mAb against CD229 that works on paraffin-embedded tissue and lack of reports describing its expression in reactive human tissues and B-cell lymphomas, prompted us to develop a specific mAb that could work on formalin-fixed paraffin-embedded (FFPE) tissues with which we could investigate the potential diagnostic value of CD229 as a marker for B-cell malignancies. Here, LY9 is linked to B-cell non-Hodgkin lymphoma.