Although tissue architecture is completely effaced in CLL LN, we found that the Notch ligand DLL4 was widely expressed in the vascular endothelium (Supplemental Fig. 1) and, importantly, it was also expressed by some CD68+ cells in both NOTCH1-mutated and -unmutated cases (Fig. 2). Here, CD68 is linked to B-cell chronic lymphocytic leukemia.