A Multicenter Retrospective Comparison Between Systemic Mastocytosis with T(8;21) AML and KIT Mutant T(8;21) AML.

Systemic mastocytosis (SM) is a subset of rare neoplasms characterized by clonal proliferation of aberrant mast cells (MCs) and their accumulation in >= 1 extracutaneous organs, which typically associates with activating KIT mutations.(1) SM with an associated hematological neoplasm (AHN) is the second most common type of SM in Mayo series (similar to 40%),(2) with challenging diagnosis because the mast cell infiltration may hide behind the AHN component and vice versa.(3-5) This is particularly applicable to acute myeloid leukemia (AML) because the histological examination of bone marrow (BM) has not been established as a standard diagnostic tool. Moreover, the concomitant hematological neoplasm often shares a KIT mutation and/or other clonal genetic abnormalities with neoplastic MCs. AML with t(8;21) (q22;q22)/RUNX1::RUNX1T1 [t(8;21) AML] represents 4% to 8% of all AMLs, which is categorized to the genetically favorable risk group.(6) Meanwhile, KIT mutations, most frequently at position D816, are detectable in up to 20% to 47% of patients with t(8;21) AML and associate with decreased remission duration and inferior overall survival (OS).(7-10) Previous case reports, case-series, and/or literature reviews have described the potential association of KIT mutant t(8;21) AML [KITpos t(8;21) AML] with underlying SM.(11)(,)(12) Owing to a lack of literature on investigating similarities and differences between SM-t(8;21) AML and KITpos t(8;21) AML, we carried out this retrospective cohort study from multiple Chinese centers to compare clinical and molecular features between these 2 groups. Between January 2009 and December 2022, 24 patients with SM-t(8;21) AML and 212 with KITpos t(8;21) AML diagnosed and treated in 16 Chinese centers were eligible. All patients were screened for SM by BM smear, flow cytometry, and/or BM histological examination. Details of the study design, patient population, treatment regimen, and statistical analysis have been described in supplemental Data. This study was approved by the responsible ethics committees and performed in accordance with the Declaration of Helsinki.