ESR1 and gastrointestinal stromal tumor: Resistance mutations (primary and/or acquired) that could help avoid non-beneficial therapies were also observed and included SDH loss, PDGFRAD842V, and KIT mutations specifically associated with imatinib resistance in GIST, ESR1 mutations potentially associated with anti-estrogen resistance in endometrial stromal sarcoma, inactivating TP53 mutations associated with MDM2 inhibitor resistance, and RB1 deletion associated with resistance to CDK4 inhibitors in dedifferentiated liposarcoma59–65.