Pathology & imaging recommendations:  • GIST morphology should be described as spindle cell, epithelioid or mixed.  • For all resected specimens, size (in cm) and mitotic count/5 mm2 should be reported.  • At a minimum GISTs should be stained with CD117 or DOG1. All CD117/DOG1 negative GISTs should include SDHB IHC and an expanded immunohistochemical and molecular panel to separate them from SDH-deficient GISTs and other mesenchymal neoplasms.  • Molecular testing should be done in all metastatic and unresectable GISTs, as well as GISTs with moderate- or high-risk stratification.  • Molecular testing should include at least KIT and PDGFRA (deoxyribonucleic acid, DNA testing for known activating mutations).  • SDHB IHC should be done in all suspected SDH-deficient GISTs and GISTs without an identified mutation. NTRK or FGFR fusion testing (RNA testing) may be considered in select cases.  • CECT scan of the abdomen/pelvis is used in the initial staging of GIST tumours via biphasic or triphasic technique.  • MRI is alternatively used, especially in local stages of rectal GIST tumours.  • A CT scan of the chest is not routine but may be done for select cases with bulky intrabdominal disease.  • PET/CT imaging can be used for rapid evaluation of response or surgical resection of liver metastasis.