Online Articles: Clinical and Laboratory ObservationsPrimary Bone Anaplastic Large Cell Lymphoma Masquerading as Ewing Sarcoma: Diagnosis by Anchored Multiplex PCRHue, Susan Swee-Shan MBBS, PhD, FRCPA*; Iyer, Prasad MBBS, MD, FRCPCH†,‡; Toh, Luke Han Wei MBBS, FRCR, MMed‡,§; Jain, Sudhanshi BSc∥; Tan, Enrica Ee Kar MBBS, MRCPCH†; Sittampalam, Kesavan MBBS, FRCPA¶; Lian, Derrick Wen Quan MBBS, FRCPath‡,∥; Chang, Kenneth Tou En MBChB, FRCPath‡,∥Author Information *Department of Pathology, National University Hospital †Department of Paediatric Subspecialties, Haematology-Oncology Service, KK Women’s and Children’s Hospital Departments of §Diagnostic and Interventional Imaging ∥Pathology and Laboratory Medicine, KK Women’s and Children’s Hospital ¶Department of Anatomic Pathology, Singapore General Hospital ‡Duke-NUS Medical School, Singapore, Singapore S.S.-S.H. and P.I. contributed equally to this work. Supported by the VIVA-KKH Pediatric Brain and Solid Tumor Program. The authors declare no conflicts of interest. Reprints: Kenneth Tou En Chang, MBChB, FRCPath, Department of Pathology and Laboratory Medicine, KK Women’s and Children’s hospital, 100 Bukit Timah Road, Singapore 229899, Singapore (e-mail: [email protected]). Journal of Pediatric Hematology/Oncology: March 2018 - Volume 40 - Issue 2 - p e103-e107 doi: 10.1097/MPH.0000000000000839 Buy Metrics Abstract A 3-year-old boy presented with pathologic fracture of the left proximal femur. Magnetic resonance imaging revealed an aggressive expansile bony mass associated with cortical destruction and surrounding myositis. Computed tomography–guided biopsy revealed a monomorphic small round blue cell tumor by histology. CD99 immunoreactivity and low-level EWSR1 gene translocation by break-apart fluorescent in situ hybridization initially favored a diagnosis of Ewing sarcoma and chemotherapy commenced. Subsequent molecular evaluation by an anchored multiplex polymerase chain reaction–based assay (Archer FusionPlex Sarcoma Panel) revealed a nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) gene fusion. The diagnosis was then amended to primary bone ALK-positive anaplastic large cell lymphoma and the chemotherapy regimen was modified accordingly. This report illustrates the value of this molecular assay in establishing the correct diagnosis of a very rare malignancy masquerading as another tumor type. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.