Abstract
Lymphoma is the most common neoplasia in cats and is frequently linked with concurrent retroviral infections. Despite preventive strategies, feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) remain endemic in many parts of the world, with FeLV significantly shortening the lifespan of infected cats. In Brazil and other low-income countries, the incidence of FeLV and FIV remains high. However, the distribution of these retroviruses across South America is still unclear, and their correlation with the anatomical and clinical features of feline lymphoma remains poorly understood. Gaining a deeper understanding of these associations could lead to more effective disease control strategies and better-defined chemotherapy protocols. In this study, we examined the geographical distribution and clinical presentations of feline lymphoma in retrovirus-positive cats in Brazil. A modified bias risk analysis assessed the quality of published studies, and a map was created to highlight areas in need of further research. Initial screening of 703 studies identified 29 relevant ones, encompassing 607 cats with feline lymphoma. After bias analysis, 273 cases were included in this review: 190 were FeLV-positive and FIV-negative, 98 were FeLV-negative and FIV-negative, and 15 were FeLV-negative and FIV-positive. Cases were reported from six Brazilian states and the Federal District of Brazil (2000-2023). The anatomical location of lymphoma varied depending on the cats' viral status, with notable differences in intestinal and mediastinal manifestations. FeLV-negative cats showed an 11.1-fold increased risk (95 % CI=6.0-20.0) for intestinal lymphoma, while FeLV-positive cases had a 7.5-fold increased risk (95 % CI=3.7-15.6) for mediastinal lymphoma. Due to the scarcity of FIV-related cases, analyzing associations was not feasible. Given the apparent association between FeLV-positive status and lymphoma location, further research into this neoplasm is strongly encouraged. We also recommend widespread retrovirus testing and expanded FeLV vaccination efforts in Brazil.