title: FLT3 mutations in myeloid sarcoma.
abstract: Myeloid sarcoma is an extramedullary tumour that typically occurs in the setting of acute myeloid leukaemia (AML), or myeloproliferative disorders. In AML, two types of mutations in Fms-like tyrosine kinase 3 (FLT3) have been described; internal tandem duplications (ITD) and point mutations at aspartic acid residue 835 (D835). We analysed 24 myeloid sarcoma specimens from 20 patients for FLT3 ITD and D835 mutations. FLT3 ITD mutations were identified in three of 20 cases (15%); no D835 mutations were identified. The ITD inserts ranged in size from 33 to 198 base pairs (bp) and represented approximately 20-40% of the FLT3 alleles. Two cases showed discordance in FLT3 ITD mutational status. In one case, the leukaemia specimen was positive for a FLT3 ITD mutation and the myeloid sarcoma specimen was negative. In the second case, the myeloid sarcoma was positive for a FLT3 ITD mutation at diagnosis, but negative in subsequent relapse samples. Our findings suggest that small molecule inhibitors of FLT3 may be useful therapeutic agents for treatment of myeloid sarcomas-containing FLT3 mutations, however, the potential for discordance between the leukaemia and myeloid sarcoma, necessitates that the myeloid sarcoma tumour itself be analysed for FLT3 mutations.
authors.affiliation: Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, MD, USA.
authors.forename: M Ali
authors.initials: MA
authors.lastname: Ansari-Lari
authors.forename: Ching-Fen
authors.initials: CF
authors.lastname: Yang
authors.forename: Rima
authors.initials: R
authors.lastname: Tinawi-Aljundi
authors.forename: Lisa
authors.initials: L
authors.lastname: Cooper
authors.forename: Patricia
authors.initials: P
authors.lastname: Long
authors.forename: Robert H
authors.initials: RH
authors.lastname: Allan
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Borowitz
authors.forename: Karin D
authors.initials: KD
authors.lastname: Berg
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Murphy
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004252:DNA Mutational Analysis / Q000379:methods; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D006801:Humans; D007223:Infant; D007951:Leukemia, Myeloid / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics; D017354:Point Mutation; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*; D020080:Tandem Repeat Sequences / Q000235:genetics; D051941:fms-Like Tyrosine Kinase 3
chemical_list: D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; C497970:FLT3 protein, human; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3