Molecular findings in bone marrow samples of myeloid sarcoma

Abstract Introduction/Objective Myeloid sarcoma is a rare extramedullary manifestation of acute myeloid leukemia. There are very few studies regarding molecular findings in myeloid sarcoma or their associated myeloid leukemia Methods/Case Report We evaluated cases of myeloid sarcoma with concurrent or prior bone marrow studies diagnosed as acute myeloid leukemia, from 2014 to 2021. We searched our Anatomic pathology information system for the terms ‘myeloid sarcoma’ or ‘leukemia cutis’. Out of 58 cases of myeloid sarcoma, ten had next generation sequencing studies (FoundationOne Heme) performed on bone marrow aspirate. Results-There were 7 male and 3 female patients. Age range was from 1-79 yrs. Myeloid sarcoma involved the skin (n=7) or soft tissue (n=3). Most common mutated genes were KMT2A/MLL (n=4, all translocations/fusions) followed by AXL1 (n=3), TP53 (n=3), NRAS (n=2), TET2 (n=2) and CEPBA (n=2). KMT2A fusion partners were MLLT1/ENL (n=1), MLLT3 (n=1), and MLLT10/AF10 (n=2). In all except for one case that harbored KMT2A/MLL fusions, karyotype also showed translocation of KMT2A. Only one case had both an AXL stop codon and a KMT2A translocation, otherwise AXL1/CEBPA mutated cases and KMT2A/MLL mutated cases were mutually exclusive. Other mutated genes were PHF6, BRCA2, DNMT3A, NPM1, RAD21, CBL, KMD6A, and NF1; each found in one case. Results (if a Case Study enter NA) Our result support the notion of higher risk of myeloid sarcoma in KMT2A and TP53 mutated AMLs. Except for absence of spliceosomes mutation, the incidence of mutated genes and functional categories in our series is concordance with two previously published studies. Conclusion Our result support the notion of higher risk of myeloid sarcoma in KMT2A and TP53 mutated AMLs. Except for absence of spliceosomes mutation, the incidence of mutated genes and functional categories in our series is concordance with two previously published studies.