Descriptive study of feline lymphoma over a period of 7 years

Objectives: Lymphoma is the most common neoplasm seen in cat but stills difficult to predict the course of disease and response to treatment. Prevalences of the different anatomical forms differ markedly within studies, presumably related to diagnostic procedures, genetic and environmental factors. The aim of the study was to describe a feline lymphoma population according to anatomic location, diagnostic method, FIV/FeLV infection and treatment approach. Material and Methods: The clinical data were retrospectively collected. The inclusion criteria were cats (N=150) with lymphoma, diagnosed by cytology, histopathology or both. Results: Over the period 2017-2024, 20 new cases of lymphoma were diagnosed on average per year, with a notorious increase in the last 3 years. Most of diagnosis were made through cytology alone (69%; 104/150), cytology and histopathology (25%; 38/150) and histopathology only (6%; 8/150). The most frequent anatomic locations were alimentary (45%; 68/150), followed by extranodal (20%; 30/150), mediastinic (17%;25/150), multicentric (8%; 13/150), nodal (5%;7/150) and leukemic (5%; 7/150). Regarding FIV and FeLV status, 66% (99/150) of the cats were tested, being 33% (49/150) negative, while 25% (38/150) were FeLV positive, 7% (10/150) were FIV positive, while 1% (2/150) was positive for both viruses. About 45% (67/150) of the cats were treated, 34% (52/150) were not and 21% (31/150) were lost to follow up. Within the treated animals, 22 were treated with palliative therapy, 17 with CHOP, 17 with chlorambucil and prednisolone, 2 with lomustine and prednisolone and 8 with COP. Conclusion: The worldwide shift in the anatomical subtype of feline lymphoma to the alimentary form also occurred in our study population, although the relatively high percentage of FeLV positive animals. Prognostic conclusions in cats with lymphoma are difficult because of the limited animals treated for the same anatomical form, subtype classification, stage, viral status and chemotherapy protocol. More studies are warranted. Keywords: Cat, Lymphoma, FeLV, Neoplasia, Chemotherapy. Funding: This work is part of the project “New perspectives on cytological and immunocytochemical characterization of Feline Lymphoma – trying to stablish an Early Prognosis” funded by FMV-ULusofona 2023-2024 (Acronym: FL).