Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 19 2 2025 04 20 189 192 EN Yuri Medeiros Department of Stomatology, A.C.Camargo Cancer Center, São Paulo, SP, Brazil Dandara Oliveira Department of Stomatology, A.C.Camargo Cancer Center, São Paulo, SP, Brazil Agnaldo Prata Júnior Department of Stomatology, A.C.Camargo Cancer Center, São Paulo, SP, Brazil Laura Souza Department of Stomatology, A.C.Camargo Cancer Center, São Paulo, SP, Brazil Clóvis Pinto Department of Anatomic Pathology, A.C.Camargo Cancer Center, São Paulo, SP, Brazil Graziella Jaguar Department of Stomatology, A.C.Camargo Cancer Center, São Paulo, SP, Brazil Fabio Alves 1) Department of Stomatology, School of Dentistry, São Paulo University, São Paulo, SP, Brazil 2) Department of Stomatology, School of Dentistry, São Paulo University, São Paulo, SP, Brazil 2024 01 04 2024 04 02 Although there have been some reports of oral hairy leukoplakia (OHL) in patients with hematologic neoplasms, to the best of our knowledge, this study is the first to report this lesion affecting a patient with polycythemia vera. A 54-year-old male patient diagnosed with polycythemia vera presented with non-removable white patches with a rough surface on the bilateral border of the tongue. According to clinical, histopathological, and in situ hybridization features, OHL was established. Two months after diagnosis, the patient developed splenomegaly and initiated ruxolitinib. Bone marrow biopsy showed post-polycythemia vera myelofibrosis. The patient underwent allogeneic haploidentical hematopoietic stem-cell transplant, achieving complete remission of the oral lesion. OHL is an important marker of immunosuppression. In the present case, OHL was diagnosed during the progression of polycythemia vera to myelofibrosis, and its early diagnosis may have contributed to a better clinical outcome. https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/2150 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/2150/1084