The new tool "KIT" in advanced systemic mastocytosis.

Mastocytosis is a rare disease characterized by KIT-driven expansion and accumulation of neoplastic mast cells in various tissues. Although mediator symptoms related to mast cell activation can impose a symptom burden in cutaneous disease and across the spectrum of systemic mastocytosis subtypes, the presence of an associated hematologic neoplasm and/or organ damage denotes advanced disease and the potential for increased morbidity and mortality. In addition to the revised 2016 World Health Organization classification of mastocytosis, a new diagnostic and treatment toolkit, tethered to enhanced molecular characterization and monitoring, is poised to transform the management of patients with advanced systemic mastocytosis (advSM). Although the efficacy of midostaurin and novel selective KIT D816V inhibitors, such as avapritinib (BLU-285), have validated KIT as a therapeutic target, the clinical and biologic heterogeneity of advSM requires that we reimagine the blueprint for tackling these diseases and use tools that move beyond KIT-centric approaches.