NTRK1 and mastocytosis: Since NTs are important for survival of MCs and treatment with KIT inhibitor (in particular imatinib and dasatinib) alone did not lead to a durable response in most patients with mastocytosis, we investigated whether TRKA activation improves neoplastic mast cell fitness in the presence of mutations of KIT and is involved in resistance of mast cells with KIT mutations to KIT inhibitors.