Faraldo, N. C.; Rosenfeld, A. d. F. S.; Brombatti, K. G.; Amorim, R. L.; Battaglia, S. T. H.; Sobral, R. A.; Fonseca Alves, C. E.

Feline intestinal lymphoma is the most common gastrointestinal neoplasm in cats and presents variable biological behavior and treatment responses. Despite its clinical importance, reliable prognostic biomarkers for this neoplasm are still lacking. This study aimed to investigate the immunohistochemical expression of Ki-67, BAX, caspase-3, and VEGF-A in feline intestinal lymphoma and evaluate their potential associations with overall survival and response to chemotherapy. Thirty cases of feline intestinal lymphoma were retrospectively analyzed. Clinical data, histopathological classification (lymphocytic vs. lymphoblastic), and immunophenotyping (B- vs. T-cell origin) were assessed. Immunohistochemistry was performed to evaluate the expression levels of Ki-67, BAX, caspase-3, and VEGF-A, which were classified as high or low. Associations between biomarker expression, lymphoma subtype, treatment status, and overall survival were analyzed via Kaplan?Meier curves and statistical comparisons. Most cases were of T-cell origin (22/30), with 17 classified as lymphocytic and 13 as lymphoblastic lymphoma. Chemotherapy significantly increased overall survival (p = 0.0008). Low expression of BAX (p = 0.0032), high expression of Ki-67 (p = 0.0184), and low expression of caspase-3 (p = 0.0222) were associated with reduced survival. VEGF-A expression was not significantly associated with survival (p = 0.0556), although a trend toward worse prognosis in high-expression cases was observed. When biomarker expression was analyzed in conjunction with chemotherapy status, the prognostic value of each marker was enhanced, with all the markers showing significant associations with survival (p < 0.0001). BAX, caspase-3, and Ki-67 expression levels are associated with prognosis in feline intestinal lymphoma, particularly when considered alongside treatment status. These markers may assist in predicting survival outcomes and tailoring therapeutic strategies in affected cats.