CAF: Cancer-associated fibroblasts; TME: Tumor microenvironment; NA: Not applicable; FAP: Fibroblast activation protein; EUS: Endoscopic ultrasound; FNB: Fine needle biopsy; PDAC: Pancreatic ductal adenocarcinoma; FAPI: Fibroblast activation protein inhibitors; PET: Positron emission tomography; CT: Computed tomography; CRC1: Colorectal cancer; OSCC: Oral squamous cell carcinoma; MMT: Mesothelial-mesenchymal transition; LCM: Laser capture microdissection. Here, FAP is linked to oral cavity squamous cell carcinoma.