Two Common Diagnostic Challenges of Juvenile Myelomonocytic LeukemiaJinjun Cheng MD PhD1,3,4*, Sarah Harney MD1, 2, David Jacobsohn MD1, 2, Reuven Schore MD1,2*Center for Cancer and Blood Disorders, Children’s National Hospital, Washington, DCDepartment of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USADivision of Pathology and Laboratory Medicine, Children’s National Hospital, Washington, DCDepartments of Pathology and Pediatrics, The George WashingtonUniversity School of Medicine and Health Sciences, Washington, District of Columbia, USA

Post-transplant lymphoproliferative disorder (PTLD) is a significant complication of solid organ transplantation due to the lifelong immunosuppression (IS), ranging from non-malignant lymphoproliferations to lymphomas. Plasmablastic lymphoma (PBL), a rare and aggressive lymphoma, usually presenting in immunocompromised individuals has been rarely reported in the post-transplant setting. Here we summarize the clinical and pathological features of two children with PBL and history of solid organ transplant.

Secondary histiocytoses are exceedingly rare and knowledge about pathophysiology and treatment is limited. We report the first known case of Philadelphia chromosome -like - B-lymphoblastic leukemia complicated by disseminated juvenile xanthogranuloma in an adolescent salvaged successfully with targeted MEK inhibition.

Pediatric cutaneous T-cell lymphoma with γδ immunophenotype is extremely rare. Only a few cases of γδ T-cell neoplasm have been reported in the literature and therefore little is known whether γδ T-cell neoplasms in children are distinct from their adult counterparts with respect to the clinicopathological presentation, behavior and prognosis. In this study, we demonstrate three unique cases with increased γδ T-cells in malignant and non-malignant skin conditions of children. All cases showed an indolent clinical course. Full integration of clinical presentation, morphology, immunophenotype, and genetics supports the correct diagnosis and guides the treatment.

Mixed Phenotype Acute Leukemia with BCL11B Copy Gain: What is the Best Strategy? Keri Toner MD1, 2, Reuven Schore MD1,2 and Jinjun Cheng MD PhD1,3,4*Center for Cancer and Blood Disorders, Children’s National Hospital, Washington, DCDepartment of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USADivision of Pathology and Laboratory Medicine, Children’s National Hospital, Washington, DCDepartments of Pathology and Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA

Severe autoimmune lymphoproliferative syndrome phenotype in a pediatric patient with a germline FAS gene variant Authors: Alexandra Dreyzin MD MS1; Jinjun Cheng MD PhD2, David Leitenberg MD PhD3, and Yaser Diab MBBS1Center for Cancer and Blood Disorders, Children’s National Hospital, Washington, DCDivision of Pathology and Laboratory Medicine, Children’s National Hospital, Washington, DCDepartment of Microbiology, Immunology and Tropical Medicine, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA.