NF1 and neurofibromatosis type 1: This group is heterogeneous, not typically responsive to imatinib or other typical tyrosine kinase inhibitors (TKI), and includes SDH-deficient tumors (14%), tumors with mutations in NF1 (type 1 neurofibromatosis), BRAF V600E, and NTRK (0.5% each), and other rare mutations.