Feline paraneoplastic hypereosinophilic syndrome associated with lymphocytic intestinal lymphoma

Alimentary lymphocytic lymphoma (AL) is the most prevalent neoplastic subtype in cats. T-cell neoplasms have been associated with eosinophil chemotaxis and, consequently, paraneoplastic hypereosinophilic syndrome. This report describes a case of marked hypereosinophilia in a cat with AL, consistent with a paraneoplastic hypereosinophilic syndrome, based on clinical findings. A 13-year-old neutered male Persian cat, negative for feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV), with a history of frequent vomiting, presented with a mild increase in abdominal volume on palpation, suggestive of mesenteric lymph node enlargement. Blood profile revealed marked leukocytosis (81,500 leukocytes/µL) due to severe eosinophilia (69,000/µL), consisting exclusively of segmented eosinophils. Abdominal ultrasonography showed lymphadenomegaly and increased echogenicity of the meso-omentum, suggestive of an infiltrative neoplastic process. Following suspicion of lymphoma, intestinal biopsy and bone marrow (BM) sampling were performed. BM evaluation was consistent with a myeloproliferative process, with eosinophilic lineage involvement. Histopathological examination of the duodenum, jejunum, and mesenteric lymph node confirmed the diagnosis of AL. Treatment with prednisolone, chlorambucil, and cobalamin was instituted. One month after treatment, the cat was clinically stable, with a total eosinophil count of 22,000/µL. After six months, eosinophil counts decreased to 9,030/µL, and abdominal ultrasonography showed no abnormalities. This report highlights the importance of investigating AL in cats presenting with marked hypereosinophilia.