In a retrospective analysis of flow cytometry data used to assess the feasibility of a cell-based proteomic approach to FCM by unsupervised cluster analysis, Habib and Finn showed that 14 atypical CLLs (out of 81 patients with CLL) were skewed toward “atypical” CLL characterized by high CD20, CD22, FMC7, and light chain, and low CD23. Here, MS4A1 is linked to B-cell chronic lymphocytic leukemia.