Systemic mastocytosis (SM) has greatly benefited from the broad application of precision medicine techniques to hematolymphoid neoplasms. Sensitive detection of the recurrent KIT D816V mutation and use of next generation sequencing (NGS) panels to profile the genetic landscape of SM variants have been critical adjuncts to the diagnosis of SM, subclassification of SM, and development of clinical-molecular prognostic scoring systems. Multilineage KIT involvement and multi-mutated clones are characteristic of advanced SM, especially SM with an associated hematologic neoplasm (SM-AHN). A major challenge is how to integrate conventional markers of mast cell disease burden (percent bone marrow mast cell infiltration, serum tryptase levels) with molecular data (e.g. serial monitoring of both KIT D816V variant allele frequency and NGS panels) to lend more diagnostic and prognostic clarity to the heterogeneous clinical presentations and natural histories of advanced SM. The approval of the multikinase / KIT inhibitor midostaurin has validated the paradigm of KIT inhibition in advanced SM, while the efficacy and safety of 2nd generation agents, such as the switch-control inhibitor ripretinib (DCC-2618) and the D816V-selective inhibitor avapritinib (BLU-285) are being further defined in ongoing clinical trials. Looking forward, perhaps the most fruitful marriage of the advances in molecular genetics and treatment will be the design of adaptive basket trials that combine histopathology and genetic profiling to individualize treatment approaches for patients with diverse AHNs and relapsed/refractory SM.Copyright © 2020 American Society of Hematology.
