Extraordinary Case ReportAggressive CD4/CD8 Double-Negative Primary Cutaneous T-Cell Lymphoma With Dural Invasion: A Rare Presentation of Mycosis Fungoides?Haghayeghi, Koorosh MD, PharmD*; Robinson-Bostom, Leslie MD†; Olszewski, Adam MD‡; Jackson, Cynthia L. PhD*; Patel, Nimesh R. MD*; Sewastianik, Tomasz PhD§,¶; Carrasco, Ruben D. MD, PhD§,‖; Shanmugam, Vignesh MD‖; Treaba, Diana O. MD*Author Information *Department of Pathology and Laboratory Medicine, Rhode Island Hospital and Lifespan Medical Center, Warren Alpert Medical School of Brown University, Providence, RI; †Department of Dermatology, Rhode Island Hospital and Lifespan Medical Center, Warren Alpert Medical School of Brown University, Providence, RI; ‡Division of Hematology Oncology, Rhode Island Hospital and Lifespan Cancer Center, Warren Alpert Medical School of Brown University, Providence, RI; §Department of Oncologic Pathology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA; ¶Department of Experimental Hematology, Institute of Hematology and Transfusion Medicine, Warsaw, Poland; and ‖Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA. Correspondence: Diana O. Treaba, MD, Department of Pathology and Laboratory Medicine, Rhode Island Hospital and Lifespan Medical Center, 593 Eddy Street, Providence, RI 02903 (e-mail: [email protected]). The authors declare no conflicts of interest. The abstract of this study was presented at the 56th American Society of Dermatopathology Annual Meeting; October 19, 2019. The American Journal of Dermatopathology: January 2021 - Volume 43 - Issue 1 - p 63-66 doi: 10.1097/DAD.0000000000001725 Buy Metrics Abstract Mycosis fungoides (MF) is primarily characterized by epidermotropic CD3+/CD4+/CD45RO+ memory T cells. CD4/CD8 double-negative MF is an uncommon variant with no presumed prognostic significance. Despite the variability in the clinical course and presentation of MF, most cases behave indolently. About 5% of patients, however, advance to stage IV with visceral organ involvement. Central nervous system metastasis in MF is rare with no known cases of direct central nervous system invasion by MF to date. We report an exceedingly rare locally aggressive case of CD4/CD8 double-negative MF with direct dural invasion and underline pertinent diagnostic challenges encountered in our case. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.