Original ArticlesEmbryonal Rhabdomyosarcoma of the Ovary and Fallopian Tube Rare Neoplasms Associated With Germline and Somatic DICER1 MutationsMcCluggage, W. Glenn FRCPath*; Apellaniz-Ruiz, Maria PhD†,‡; Chong, Anne-Laure BSc†,‡; Hanley, Krisztina Z. MD§; Velázquez Vega, Jose E. MD∥; McVeigh, Terri P. PhD¶; Foulkes, William D. MBBS, PhD†,‡Author Information *Department of Pathology, Belfast Health and Social Care Trust, Belfast, Northern Ireland ¶Cancer Genetics Unit, Royal Marsden NHS Foundation Trust, London, United Kingdom †Department of Human Genetics, McGill University ‡Cancer Axis, Lady Davis Institute, Jewish General Hospital, Montréal, QC, Canada §Department of Pathology, and Laboratory Medicine, Emory University Hospital ∥Department of Pathology and Laboratory Medicine, Children’s Healthcare of Atlanta and Emory University, Atlanta, GA Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: W. Glenn McCluggage, FRCPath, Department of Pathology, Belfast Health and Social Care Trust, Grosvenor Road, Belfast BT12 6BA, United Kingdom (e-mail: [email protected]). The American Journal of Surgical Pathology: June 2020 - Volume 44 - Issue 6 - p 738-747 doi: 10.1097/PAS.0000000000001442 Buy Metrics Abstract DICER1 mutations (somatic or germline) are associated with a variety of uncommon neoplasms including cervical and genitourinary embryonal rhabdomyosarcoma (ERMS). We report a primary ovarian and 2 primary fallopian tube ERMS occurring in 60-, 13-, and 14-year-olds, respectively. The 3 neoplasms exhibited a similar morphologic appearance being polypoid and containing edematous hypocellular areas and hypercellular foci composed of small cells with scant cytoplasm exhibiting rhabdomyoblastic differentiation (desmin, myogenin, myoD1 positive). There was cellular cartilage in all cases and extensive foci of anaplasia, eosinophilic globules, and bone/osteoid in 1 case each. All 3 neoplasms exhibited DICER1 mutations; in 1 of the tubal cases, the patient had a germline mutation and in the other 2 cases, the DICER1 mutations were somatic. Accompanying DICER1 “second hits” were identified in all cases. In 2 of the neoplasms, SALL4-positive glandular structures were present which we speculate may represent an unusual primitive “metaplastic” phenomenon. Our study adds to the literature on ERMS at unusual sites associated with DICER1 mutations. ERMS arising at such sites, especially when they contain cartilage or bone/osteoid, are especially likely to be associated with DICER1 mutations. Pathologists should be aware of this as these may be the sentinel neoplasms in patients with DICER1 syndrome and confirming a germline mutation can facilitate the screening of the individual and affected family members for other neoplasms which occur in this syndrome. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.