ABSTRACT Introduction: Acute lymphoblastic leukemia (ALL) presents a poor prognosis in adults. The adoption of pediatric protocols has been changing this scenario, especially for adolescents and young adults (AYA). Objective and method: We aimed to evaluate a consecutive series of patients treated at the State Institute of Hematology of Rio de Janeiro between 2012 and 2020, focusing on the AYA subgroup. Result: The B-ALL was the most frequent subtype (81.6%) and AYA, the predominant age group (57.7%). The median overall survival (OS) was 9.4 months. High early mortality was observed and sepsis was the main cause of death. Better OS results were noted in AYA, in comparison to over 39y (13.3 × 6.2 months, respectively), the Berlin-Frankfurt-Münster (BFM) being the protocol of choice in this group. Conclusion: The use of the pediatric protocol seems to improve the OS of AYA, however, high rates of deaths from infection were observed, demonstrating the need for advances in the Brazilian public system clinical support. Introduction ALL (ALL scenario AYA. . (AYA) method 201 2020 subgroup Result BALL B 81.6% 816 81 6 (81.6% 57.7%. 577 57.7% 57 7 (57.7%) (OS 94 9 4 9. months death y 13.3 133 13 3 (13. 62 2 6. respectively, respectively , respectively) BerlinFrankfurtMünster Berlin Frankfurt Münster BFM (BFM Conclusion however support (AYA 20 202 81.6 8 (81.6 57.7 5 (57.7% 13. 1 (13 81. (81. 57. (57.7 (1 (81 (57. ( (8 (57 (5

Asbtract Introduction This study aimed to determine whether cytokine receptor-like factor 2 (CRLF2) antigen expression evaluated using multiparametric flow cytometry (MFC) could predict the genotype of CRLF2 and Janus kinase 2 (JAK2) status for application in the diagnosis of pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Methods A total of 321 BCP-ALL bone marrow samples were collected, 291 at diagnosis and 13 at first relapse, while 17 samples were excluded due to low cellular viability. The CRLF2 antigen expression was evaluated using flow cytometry (percentage of positivity and median fluorescence intensity [MFI]). The CRLF2 transcript levels were assessed via quantitative reverse transcription polymerase chain reaction using SYBR Green. The CRLF2 rearrangements (CRLF2-r) were identified using the CRLF2 break-apart probe via fluorescence in situ hybridization. Sanger sequencing was performed to identify the JAK2 exon 16 mutations. Results We observed that 60 of the 291 cases (20.6%) presented CRLF2 antigen positivity, whereas the CRLF2 transcript overexpression was found in 19 of 113 cases (16.8%). The JAK2 mutation was found in four out of 116 cases (3.4%), all of which had CRLF2 ≥10% of positive cells and intermediate or high MFI (p < 0.0001). In addition, in the 13 cases with the CRLF2-r, a positive correlation was found with the CRLF2 antigen intermediate (61.5%) MFI (p= 0.017). Finally, the CRLF2-positive antigen was identified in the BCP-ALL subclones. Conclusion The identification of the CRLF2 antigen using the MFC, based on the percentage of positivity and MFI values, is a useful tool for predicting JAK2 mutations and CRLF2-r. receptorlike receptor like CRLF (CRLF2 MFC (MFC JAK (JAK2 Bcell B cell BCPALL. BCPALL BCP ALL . (BCP-ALL) 32 collected 29 1 relapse viability MFI. [MFI]) Green CRLF2r CRLFr r (CRLF2-r breakapart break apart hybridization 6 20.6% 206 20 (20.6% 11 16.8%. 168 16.8% 8 (16.8%) 3.4%, 34 3.4% , 3 4 (3.4%) 10 ≥10 p 0.0001. 00001 0.0001 0 0001 0.0001) addition CRLF2r, r, CRLF2-r 61.5% 615 61 5 (61.5% p= 0.017. 0017 0.017 017 0.017) Finally CRLF2positive CRLFpositive subclones values CRLF2r. r. (CRLF (JAK (BCP-ALL [MFI] 20.6 (20.6 16.8 (16.8% 3.4 (3.4% ≥1 0000 0.000 000 61.5 (61.5 001 0.01 01 [MFI 20. (20. 16. (16.8 3. (3.4 ≥ 0.00 00 61. (61. 0.0 (20 (16. (3. (61 0. (2 (16 (3 (6 ( (1