Tumor-supporting niche in FL. Three main cell subsets have been shown to support FL B-cell growth: (1) FL TAMs overexpress IL-15 that triggers STAT5-dependent FL B-cell activation, as well as DC-SIGN that aggregates FL-mannosylated BCR; (2) expanded FL Tfh activate directly malignant B cells through CD40L and IL-4 and favor indirectly the growth of the tumor by stimulating TAM and stromal cells through IL-4; and (3) stromal cells are committed to lymphoid stromal differentiation, in agreement with their contact with TNF-expressing malignant B cells, Tfh, and tumor-associated neutrophils (TAN), and they overexpress CCL2 and IL-8, thus more efficiently recruiting TAM and TAN. FL stromal cells are involved in malignant B-cell recruitment and survival through the release of chemokines and hedgehog (Hh) ligands.