(A) Cellular components of the tumor stroma include blood and lymphatic vessels, infiltrating and resident leukocytes, various populations of fibroblasts, and mesenchymal support cells unique to each tissue environment. The immune contexture is defined as the type, density, functional orientation, and location of immune cells within distinct tumor regions. A spectrum of soluble cytokines and chemokines regulate the entry of immune cells into tumors, which then have different effects on tumor progression. All types of immune cells are present in the tumor, including macrophages, DCs, mast cells, NK cells, naive and memory lymphocytes, B cells, and effector T cells (including various subsets of T cells: Th cells, Th1, Th2, Th17, Tregs, Tfh, and CTLs). Immune cells can be located in the core of the tumor, in the invasive margin, or in the adjacent TLSs. Few CD8⁺ T cells are seen in human TLSs, which are similar to secondary follicles in lymph nodes. TLSs contain naive and memory T cells, Tfh cells, B cells, and mature DCs. FDC, follicular DC. (B) High expression levels of various immune parameters that define a Th1 immune contexture, as well as the presence of Tfh cells, B cells, CXCL13, IL-21, and IL-15, are associated with prolonged DFS and/or improved OS in CRC (figures adapted from refs. 16, 23).