Abstract
Introduction
Almost all neoplasms have their prognosis determined by cytogenetic and molecular factors, which determines a tailored approach for each case. According to the World Health Organization, every case of Acute Lymphoblastic Leukemia (ALL) must be classified not only immunophenotypically but also from a genetic point of view. Over the last few years, it has been recognized the differences in incidence and genetic profile of ALL from Latin America (LA). In Brazil, a large country with a distinctive ethnical background when compared to the rest of LA, few reports on ALL have been published and there is a limited availability of genetic tests for classification, especially in public health service.
Objective
To describe cytogenetic (karyotype and fluorescence in situ hybridization, FISH), molecular markers and World Health Organization (WHO) -2016 classification of diagnostic samples sent to two reference centers in Brazil.
Material and Methods
This is a cross-sectional study involving patients diagnosed with ALL from January 2014 to May 2018. Diagnostic bone marrow specimens were analyzed by G band conventional karyotyping (Nomenclature according International System for Human Cytogenomic 2016) (n: 157), molecular markers [(genic fusions by RT-PCR - BCR-ABL1 (n: 96), TCF3-PBX1 (n: 77), ETV6-RUNX1 (n: 83), KMT2A-AFF (n:74)] and B-ALL multi-probe FISH (n:54) were employed according to manufacturer's recommendations and following international guidelines. It was attempted to classify all cases by WHO-2016, as well as by age. Samples with no metaphases, non-conclusive or without molecular tests were considered non-classifiable
Results
Samples from 157 ALL patients at diagnosis were analyzed. Median age was 8 years old (1 month - 88 years) [6 (3.8%) cases had less than 12 months; 99 (63%) between 1 to 15 years; 22 (14%) between 16 and 39 years and 30 (19.1%) older than 40 years]. The majority were B cell lineage ALL (93%). Thirty cases were excluded due to missing immunophenotyping, karyotype and/or molecular studies. Alterations were detected in 94 (74%) of 127 cases [88 (76%)/116 in B-ALL and 6 (54%)/11 in T-ALL. It was possible to classify by WHO 2016 B-ALL subtypes 116 cases, all of them stratified by age groups (Graphic 1).
Conclusion
Our results are consistent with the literature, showing that KMT2A rearrangement predominates in infant ALL, while a pediatric age range from 1 to 15 years old, with a predominance of good prognostic subtypes: hyperdiploidy and ETV6-RUNX1. In adults, there is predominance of the BCR-ABL1 subtype, which seems to be more frequent than non-Latin cohorts. B-ALL NOS was detected in 27.8% of the cases, predominating in the age group of 16 to 39 years, which may correspond to Ph-like ALL, a recently described subtype linked to a worse prognosis and seemingly more common in latinos.
Figure. Figure.
Disclosures
No relevant conflicts of interest to declare.
Risk of malignancy associated with diagnostic categories of the proposed World Health Organization International System for reporting pancreatobiliary cytopathology