FMS-related tyrosine kinase 3 internal tandem duplication (FLT3-ITD): a villain among others

cute myeloid leukemia (AML) is the most frequent acute eukemia of adult patients with an estimated 10,070 new cases n Brazil in 2016. Most of the cases are de novo, without a efined etiology, and around two thirds of the patients will die f the disease, according to the Instituto Nacional de Câncer INCA).1 Genetic aberrations may help to differentiate patients ho have a good from those with a dismal prognosis. In fact, chromosomal abnormalities detected by G-banding aryotype and gene rearrangements revealed by molecular ests are important tools to stratify patients into favorable, ntermediate or unfavorable prognoses. The World Health rganization (WHO) classification of hematopoietic tumors ists recurrent genetic abnormalities.2 FMS-related tyrosine kinase 3 (FLT3), a tyrosine kinase eceptor usually expressed in hematopoietic progenitors, is he most common genetic lesion in AML with mutations etected in from 25% to 40% of the cases.3 These mutations ay occur in any subtype of AML (including acute promylocytic leukemia – APL), and are frequent with the normal aryotype or t(6;9). There are two main types of mutations: internal tandem uplication (ITD), which is the most common (∼25% of cases), nd a point mutation (D835) (∼5%).4 Except for APL, AML patients with FLT3-ITD present ncreased chance of relapse, short disease-free survival and educed overall survival, despite an unchanged complete emission rate.5 The detection of FLT3-ITD is important for rognosis particularly in those with a normal karyotype. However, there remains some controversy about the mpact of the size of FLT3-ITD fragment on the prognosis. One tudy showed that 48–60 base-pair duplications are associted with a worse outcome6 and other authors reported that t is not possible to confirm this relationship by the length of LT3-ITD alone. There is a large variation in the clinical charcteristics of patients, making it difficult to correlate data and et standards.7,8 Aiming to evaluate the length of duplication in Brazilian atients, we evaluated AML cases diagnosed from January 013 until July 2015 at the Fleury Medicina Diagnóstica laboraory according to the WHO classification using bone marrow orphology and flow cytometry immunophenotyping. We dentified 26 (29%) out of 89 AML cases with FLT3–ITD. The ean age of the patients was 54 years old (range: 13–79 years) mong others