Extraordinary Case ReportPrimary Subcutaneous Synovial Sarcoma: First Reported Subcutaneous Case Showing TLE1 ImmunoreactivityAlegría-Landa, Victoria MD*; Nájera, Laura MD†; Massa, Dolores Suárez MD†; Roustan, Gastón MD‡; Río, María del MD§; Kutzner, Heinz MD¶; Requena, Luis MD*Author Information *Department of Dermatology, Fundación Jiménez Díaz, Universidad Autónoma, Madrid, Spain; †Departments of Pathology, and ‡Dermatology, Hospital Universitario Puerta de Hierro, Universidad Autónoma, Madrid, Spain; §Department of Plastic Surgery, Hospital Universitario Puerta de Hierro, Universidad Autónoma, Madrid, Spain; and ¶Dermatopathologie Laboratory, Friedrichshafen, Germany. Correspondence: Luis Requena, MD, Department of Dermatology, Fundación Jiménez Díaz, Avda, Reyes Católicos 2, 28040-Madrid, Spain (e-mail: [email protected]). All authors have contributed to the intellectual content of this article, have made significant contributions to the conception and design, drafting, or revision of the article for intellectual content, and have given final approval to the published article. The authors declare no conflicts of interest. The American Journal of Dermatopathology: October 2018 - Volume 40 - Issue 10 - p 772-777 doi: 10.1097/DAD.0000000000001172 Buy Metrics Abstract Synovial sarcoma (SS) accounts for 5%–10% of all soft tissue sarcomas. It is a well-defined soft tissue neoplasm with biphasic and monophasic histologic subtypes and unknown histogenesis. It usually occurs in the extremities, especially the thigh-knee region of young adults. Recurrences are frequent and distant metastasis developed in approximately half of the patients. SSs are characterized by a recurrent nonrandom chromosomal translocation, t(X; 18) (p11; q11), which is considered the primary genetic event in more than 90% of cases. Only 4 cases of cutaneous and subcutaneous SSs have been published in the literature so far. We report a case of primary subcutaneous SS in the forearm of a young woman and discuss the histopathologic differential diagnosis with other similar neoplasms. This is the first reported case of primary cutaneous SS showing immunoreactivity for TLE1 in the nuclei of neoplastic cells, supporting the use of this marker for diagnosis of this rare cutaneous neoplasm. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.