MKI67 and marginal zone lymphoma: Ki67−PD1hi cells (median distance 11.3 μm) were significantly more likely to be found in close proximity to Ki67+ B-cells than were Ki67−FOXP3+ cells (median distance 35.1 μm) (Mann-Whitney test P = < 0.0001) (Fig. 5c) suggesting for the first time that infiltrating Tfh cells might have a role in driving proliferation, and hence contribute to the varying clinical course of MZL.