Impact of Molecular Evaluations in the Biology, Diagnosis and Prognostication of Patients with Mastocytosis.

Mastocytosis represents a group of rare clonal disorders characterized by accumulation of neoplastic mast cells (MC). Disease presentations range from indolent to highly aggressive forms. The discovery of somatic mutations in KIT, particularly KIT p.D816V, has revolutionized diagnosis, classification, and management of mastocytosis. KIT p.D816V, found in >85% of systemic mastocytosis (SM) cases, drives disease progression through constitutive activation of the KIT receptor. Highly sensitive techniques, such as allele-specific oligonucleotide quantitative PCR (ASO-qPCR), digital PCR (dPCR) and Flow-Super Rolling Circle Amplification (Flow-SuperRCA) have enhanced detection of KIT p.D816V, while next-generation sequencing (NGS) has allowed detection of other mutations, improving not only diagnostics and prognostication, but also monitoring of KIT p.D816V-targeted therapies. Of note, higher KIT p.D816V allele burdens, together with the presence of additional mutations in genes like DNMT3A, SRSF2, ASXL1, EZH2 and/or RUNX1, termed high risk mutations (HRM), correlate with advanced SM subtypes. Hereditary alpha-tryptasemia (HαT) is a genetic condition where increased TPSAB1 gene copy encoding alpha-tryptase usually leads to elevated serum tryptase. The incidence of HαT is increased in mastocytosis and may exacerbate mediator-related symptoms, emphasizing the importance of searching for this genetic condition in mastocytosis. To conclude, despite remaining challenges in standardization, molecular investigations may now improve diagnostics, prognostication and treatment monitoring in mastocytosis.