University of Veterinary Medicine Vienna Feline eosinophilic sclerosing fibroplasia associated with T-/natural killer-cell lymphoma Feline eosinophilic sclerosing fibroplasia (FESF) is a proliferative, inflammatory disease of the gastrointestinal tract and other sites, uncommonly diagnosed in the cat. This entity of uncertain etiology typically presents as a progressive mass lesion, mimicking a neoplastic process. In this case series, we present 17 cases of FESF associated with intralesional lymphoma. Histologic and immunohistochemical characterization of this unique lymphoma revealed that the neoplastic lymphocytes were immunopositive for CD56 and/ or CD3, suggesting a natural killer cell, natural killer T-cell, or T-cell origin. This case series represents the first description of this lymphoma subtype, for which the term eosinophilic sclerosing lymphoma is proposed. en TEXT journal article Wissenschaftlicher Artikel Articolo di rivista Text Wissenschaftlicher Artikel Text journal article Testo Articolo di rivista Cats Animals Cat Diseases Pathology Cat Diseases Diagnosis Male Female Lymphoma, T-Cell Veterinary Lymphoma, T-Cell Pathology Lymphoma, T-Cell Diagnosis Immunohistochemistry Veterinary Killer Cells, Natural Pathology Eosinophils Pathology 2024 2024 Andrea Klang Christof A. Bertram Taryn A. Donovan Linden E. Craig Ingrid Walter Birgitt Wolfesberger Brigitte Degasperi Elisabeth Baszler Barbara C. Rütgen Sabine E. Hammer Andrea Fuchs-Baumgartinger Sage