In this study, we have characterized Ig attached to the B-CLL cells surface at peptide level by performing three different sample preparation approaches (i.e., usage of a Fab preparation commercial kit, and usage of papain in solution and DTT in Ig-enriched agarose beads from CLL protein samples for the isolation of Fab and denaturation of the Ig, respectively). Here, FANCB is linked to B-cell chronic lymphocytic leukemia.