Relative to surrounding spots and non-TLS tissue, TLSs exhibited increased expression of chemokine-encoding genes CXCL13, CCL19, and CCL21; the follicular dendritic cell and germinal center–associated B cell marker CR2 (CD21); and a 12-chemokine-encoding gene signature that identified ectopic lymph node–like structures in microarray data from primary colorectal carcinoma (25) (Figure 5B). Here, CCL21 is linked to colorectal carcinoma.