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Sarcoma of the Year: Small Round Blue Cell Tumor

(P 438) ALVEOLAR RHABDOMYOSARCOMA WITH "BURKITT-LIKE" MORPHOLOGY IS ASSOCIATED WITH HIGH AMPLIFICATION OF MYCL

Location: The Liffey, Level 1

    Author(s)

  • Michael Arnold, MD PhD

    Associate Professor
    Children's Hospital of Colorado/University of Colorado
    Aurora, Colorado, United States

    • Co-Author(s)

  • WX

    Wei Xue, PhD

    University of Florida
    Gainsville, Florida, United States

    • Co-Author(s)

  • Natalie B. Collins, MD, PhD (she/her/hers)

    Instructor
    Dana-Farber/Boston Children’s Cancer and Blood Disorders Center
    Boston, Massachusetts, United States

    • Co-Author(s)

  • Sonja Chen, MD

    Assistant Professor of Pathology
    Nationwide Children's Hospital/The Ohio State University College of Medicine
    Columbus, Ohio, United States

  • Archana Shenoy, MD

    Clinical Assistant Professor and Staff Pathologist
    Nationwide Children's Hospital/The Ohio State University College of Medicine
    Columbus, Ohio, United States

  • LT

    Lisa a. Teot, MD (she/her/hers)

    Staff Pathologist and Associate Professor
    Boston Children's Hospital and Harvard Medical School
    Boston, Massachusetts, United States

  • Abha Gupta, MD MSc

    Staff Oncologist
    Princess Margaret Cancer Center
    Toronto, Ontario, Canada

  • SW

    Suzanne Wolden, MD (she/her/hers)

    Director, Pediatric Radiation Oncology
    Memorial Sloan Kettering Cancer Center
    New York, New York, United States

  • RD

    Roshni R. Dasgupta, MD MPH

    Professor of Surgery
    Cincinnati Children's Hospital Medical Center
    Cincinnati, Ohio, United States

  • RV

    Rajkumar Venkatramani, MD

    Baylor College of Medicine / Texas Children's Hospital
    Houston, Texas, United States

  • KK

    Kelly Klega, MS, MLS(ASCP)

    Dana-Farber Cancer Institute
    Boston, Massachusetts, United States

  • BC

    Brian Crompton, MD

    Co-Director for Research, Pediatric Solid Tumor Program Assistant Professor of Pediatrics, Harvard Medical School Associate Member, Broad Institute of Harvard and MIT Dana-Farber/Boston Children’s Cancer and Blood Disorders Center
    Dana-Farber Cancer Institute
    Boston, Massachusetts, United States

  • Erin Rudzinski, MD

    Medical Director of Anatomic Pathology
    Seattle Children's Hospital/University of Washington
    Seattle, Washington, United States

Objective: Alveolar rhabdomyosarcoma (ARMS) is a distinct histologic category of rhabdomyosarcoma, with approximately 80% of cases associated with FOXO1 gene fusions. Outcomes for patients with ARMS are strongly associated with the presence of FOXO1 gene fusions, and additional genetic markers are essential to better define the cohort of FOXO1 fusion negative ARMS.

Methods: We reviewed the histology of 306 diagnostic biopsies submitted to the recent Children’s Oncology Group (COG) trial ARST1431.

Results: Histologic review of biopsy specimens from ARST1431 identified two cases with ARMS histology (defined as tumor cells with uniform, round nuclei) as well as distinctive large nucleoli with coarse chromatin, amphiphilic cytoplasm and abundant karryorrhexis resembling Burkitt lymphoma. Both cases showed diffuse myogenin reactivity, confirming the diagnosis of ARMS, and both cases were negative for FOXO1 fusions by FISH testing. The cases arose in the perianal region or upper extremity, in a 2 and 1 year old patient, respectively. Additional sequencing studies identified high amplification (>50 copies) of the MYCL proto-oncogene in both cases.

Conclusion: We hypothesize that the distinctive phenotype of these two cases is driven by MYCL amplification. MYCL high amplification has been previously reported in one case of ARMS that was FOXO1 fusion negative and refractory to therapy. The previously reported case displayed similar histologic features to the cases we identified in ARST1431. These cases demonstrate that histologic features can be used to aid in identifying novel genetic signatures among cases of fusion negative ARMS. Clinical follow-up for ARST1431 will soon be available to further examine the outcome for this small but unique set of patients. However, identification of additional cases will be required to determine the clinical significance of this “Burkitt-like” histologic pattern with MYCL amplification.