The claudin 18 (CLDN18)-Rho GTPase activating protein 26 (ARHGAP26) fusion gene is frequently recurrent in diffuse GC, inducing the formation of characteristic “signet-ring cells” and promoting the activation of ras homolog family member A (RHOA) and its downstream signaling, notably the focal adhesion kinase (FAK) and YAP signaling pathways. Here, CLDN18 is linked to gastric cancer.