Infantile myofibromatosis is a mesenchymal disorder characterized by the fibrous proliferation of the skin, bone, muscle and viscera. It is the most common fibrous tumor in childhood. We present a newborn with skin and bone disease without visceral involvement, who showed good response to vinblastine and methotrexate. Clinical features, etiology, diagnosis, and treatment are reviewed.

Transient myeloproliferative disorder (TMD) is an uncommon syndrome strongly associated with abnormalities of chromosome 21. Blast transient proliferation appears most frequently at neonatal age and usually resolves spontaneously in two or three months. Two patients, a girl and a boy, with neonatal onset of TMD are reported. They both presented trisomy 21 mosaicism according to bone marrow cytogenetic analysis. Patient 1, on one end of the spectrum, showed a "classic" benign course with rapid resolution and favorable outcome. Patient 2, on the other hand, had two blast outbursts both followed by spontaneous remissions. He failed to thrive and never reached a good general condition, dying at 5 months of age from a respiratory infectious complication. The necropsy showed generalized extramedullary hemopoiesis without evidence of bone marrow blast infiltration or myelofibrosis. TMD has some clinical and laboratory features that make it unique and distinguishable from true congenital leukemia with which it may be initially mistaken. It usually has a benign course followed by a favorable outcome. As trisomy 21 mosaicism may not have overt phenotypic stigmata, it is possible that many cases of TMD in these children may have a silent, non-detected course. We also conclude that a favorable outcome is not always to be expected in TMD.

Introduction: Survival of children with acute lymphoblastic leukemia (ALL) has improved in the last decades, achieving approximately 80% in Argentina. However, relapses remain the most frequent adverse event and the identification of patients with higher risk need to be refined. Deletions in IKZF1(IKZF1del) in addition with deletion of CDKN2A, CDKN2B,PAX5 or PAR1 region define a new subgroup of patients (IKZF1plus) with higher relapse rate and poor survival. Objectives: To analyze the characteristics of patients with IKZF1del and IKZF1plus, assessing the impact of the copy number alterations in several genes on survival of pediatric ALL treated with ALLIC strategy. Methods: This is a retrospective analysis performed in the population of patients admitted from October 2009 to May 2018. Samples of 432 patients with diagnosis of ALL were collected and analyzed by MLPA P-335 (MRC-Holland) for copy number alterations of IKZF1, EBF1, JAK2, CDKN2A, CDKN2B, PAX5, ETV6, BTG1, RB1 genes and PAR1 region. IKZF1plus cases were defined as those with IKZF1del with at least one additional deletion in: PAX5, CDKN2A, CDKN2B, PAR1 region. Patients were treated with 2 consecutive ALLIC protocols, according to studies stratification. Patient characteristics were compared with chi-square and Wilcoxon-sum-rank-test. Survival probability was analyzed with Kaplan-Meier calculation and survival results compared with Log-rank-test. Results: IKZF1 was not deleted in 345 cases, IKZF1del was detected in 87 cases and 47 of them were defined as IKZF1plus. Statistically significant higher WBC, MRD+ positivity on day 15, day 33 and week 12, more BCR-ABL+ and high-risk group cases, null response and higher relapse rate were observed in the IKZF1del group (total) when comparing with IKZF1 not del, and also when comparing IKZF1plus vs IKZF1 not del + IKZF1del only. EFS (SE) and DFS (SE) probabilities were: 73 (4)% and 75 (3)% for IKZF1 not del, 66 (9)% and 70 (9)% for IKZF1del, and 20 (10)% and 21 (10)% for IKZF1plus, respectively (p<0.00001).DFS of the standard-risk group was not influenced by the presence of only 1 case of IKZF1del detected in this risk-group of patients. However, DFS of intermediate-risk patients was 41 (11)% for IKZF1plus while 70 (7)% and 73 (4)% were achieved for IKZF1del and IKZF1 not del respectively (p=0,0083). Therefore, high-risk patients with IKZF1plus achieved DFS of 12 (19)% vs 65 (7)% and 50 (21)% for IKZF not del and IKZF1del respectively (p=0.0085). DFS of patients with IKZF1del + CDKN2Adel was 30 (10)% and CDKN2A not deleted 67 (9)% (p=0.0433). DFS of patients with IKZF1del + CDKN2Bdel was 42 (12)% and 66 (9)% for CDKN2B not del. DFS of cases with IKZF1del in addition to deletion of ETV6, BTG1, EBF1 orJAK2 did not show statistically significant differences when comparing with IKZF1del + normal copy number of these genes. In addition, DFS of cases with RB1del was 36 (13)% while cases without RB1del showed 70 (3)% (p=0.0071). Conclusions: 1- Patients with IKZF1del and IKZF1plus disclosed biological features related to poor outcome. 2- IKZF1plus was associated with a poor outcome in intermediate and high-risk groups according to ALLIC stratification. 3- The addition of CDKN2Adel to IKZF1del influence the outcome. However, CDKN2Bdel did not show the same effect. 4- Copy number alterations of ETV6, BTG1, EBF1 or JAK2 did not demonstrate prognostic impact. 5- RB1 showed negative influence in survival. 6- Identification of patients with IKZF1plus at diagnosis could be very useful for improving risk-group stratification of pediatric ALL patients. Disclosures No relevant conflicts of interest to declare.

Background: The GATLA Collaborative Group has a 50 year (y) long experience of running cooperative trials for lymphomas in Argentina. Aim: Describe the outcome of pediatric patients(pts) treated according to the international cooperative work with AHOPCA and St. Jude Children's Research Hospital (11-EHP-12) adopting OEPA/COPDAC strategy for High Risk (HR) pts and ABVD for Intermediate (IR) and Low Risk (LR) pts. Methods: 11-EHP-12: Risk assignment according Stanford/Danna Farber/ SJCRH Consortium classification. LR: ABVD x 4± IFRT (20 Gy). IR: ABVD x 6 ± IFRT (20 Gy). HR: OEPA-COPDAC+IFRT (20/25 Gy). Response evaluation: LR after 4th cycle, IR and HR after the 2nd cycle. Complete Remission (CR): response &gt; 80% reduction and PET negative. Partial Remission (PR): response &gt;50% and &lt;80% reduction and/or PET positive. 170 pediatric patients (pts) were enrolled since November 2012. 133 evaluable pts. 37 on treatment and/or a follow up of less than 5 years. Sex: M/F: 85 (63,9%) /48. Median age: 13 y (range 4-18 y). Histology: nodular sclerosis 91 (68,4%), mixed celularity 31 (23.3%), lymphocyte rich 1 (0,7%), lymphocyte depleted 1 (0,7%), nodular lymphocyte predominant 8 (6,9%). Stage: I :16 (12%), II: 51 (38.4%), III: 27 (20.3%), IV: 39 (29.3%). B Symptoms: 66 (49.6%). Interim evaluation: PET/TC: 109/133 (82%), TC: 24. Distribution by risk groups: HR pts.: 77 (57,9%), IR: 35 (26,3%), LR: 21 (15,8%). Results: 5 y OS was 94% (100% for LR and IR, and 91% HR) and 5y EFS was 88% (100% for LR, 91% IR, and 84% HR). 95% of the LR pts and 72% of the IR pts did not undergo radiotherapy. 70% of the HR pts achieved CR after the 2nd OEPA and received 20 Gy IFRT. According PR or CR after 2nd OEPA, the 5y EFS in HR pts was 84% and 90% respectively. Conclusion: Thanks to this international cooperation We could significantly improve the results in Argentina compared to our previous experience (7-PHD-96: COPP-ABV x 6 + IFRT Bulky disease or PR (20/25Gy): 5yOS:85%, 5yEFS:67%), reduce the number of patients who required radiotherapy and reproduce the Euronet experience for HR pts in a different context. Figure Disclosures No relevant conflicts of interest to declare.

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