CXCR4 and gastrointestinal stromal tumor: Due to limitations in using animal models to study GIST, and the inability of PDX models to accurately reflect the TIME and clinical state of GIST disease, we cannot currently validate the in vivo chemotactic effect of CD68+ macrophages on CD20+ B cells, which promotes TLS formation via the CXCL12/CXCR4 axis.