A pitfall worth mentioning is that one type of pancreatic cancer, the pancreatic ductal adenocarcinoma (PDAC), expresses prominent FAP in the cancerous tissue and thus may have similar image presentation with IgG4-RD when using 68Ga-FAPI (Röhrich et al., 2020). The gene discussed is FAP; the disease is immunoglobulin G4-related sclerosing disease.