Andrea Klang Andrea Klang Christof A. Bertram Christof A. Bertram Taryn A. Donovan Taryn A. Donovan Linden E. Craig Linden E. Craig Ingrid Walter Ingrid Walter Birgitt Wolfesberger Birgitt Wolfesberger Brigitte Degasperi Brigitte Degasperi Elisabeth Baszler Elisabeth Baszler Barbara C. Rütgen Barbara C. Rütgen Sabine E. Hammer Sabine E. Hammer Andrea Fuchs-Baumgartinger Andrea Fuchs-Baumgartinger Sage 2024 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. PDFDocument eng 2025-04-01T08:19:21.317746Z 2024 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 2366478 b application/pdf http://creativecommons.org/licenses/by/4.0/