Immunohistochemical evaluation of cyclooxygenase-2 expression in feline nasal malignant epithelial tumours

ObjectivesCyclooxygenase-2 (COX-2), a pivotal enzyme in the cyclooxygenase family, plays a critical role in carcinogenesis. While its expression is well documented in various neoplasms in humans and dogs, data on COX-2 expression in feline neoplasms, particularly nasal malignant epithelial tumours, is limited. This study aimed to evaluate COX-2 expression in feline nasal malignant epithelial tumours through immunohistochemistry. We hypothesised that these tumours would exhibit COX-2 expression, consistent with findings in humans and dogs.MethodsFormalin-fixed, paraffin-embedded biopsy samples from feline nasal malignant epithelial tumours were retrospectively analysed for COX-2 expression by immunohistochemistry. Biopsies from cats previously treated with non-steroidal anti-inflammatory drugs were excluded. Immunohistochemistry was performed with a monoclonal rabbit antibody, with feline renal macula densa cells serving as the positive control. The immunoreactive score (IRS) combined a semiquantitative estimation of immunolabelled neoplastic cells with labelling intensity. Scores in the range of 0-1 were classified as negative, 2-3 as low, 4-8 as intermediate and greater than 8 as high COX-2 expression levels.ResultsA total of 18 feline nasal biopsies (nine adenocarcinomas, seven carcinomas, one squamous cell carcinoma and one mucinous carcinoma) were included. Clinical signs included nasal discharge, sneezing, epistaxis and inspiratory dyspnoea. COX-2 expression was not detected in any case (IRS = 0). Follow-up data were available for 7/18 cats. The overall median survival time after diagnosis in our cohort was 667 days (range 0-1642).Conclusions and relevanceIn contrast to canine nasal malignant epithelial tumours, COX-2 expression was not observed in feline nasal malignant epithelial tumours. These results suggest species-specific differences in COX-2 expression in nasal malignant epithelial tumours. Further studies evaluating other carcinogenesis pathways, such as vascular endothelial growth factor or platelet-derived growth factor, seem crucial to better understand feline nasal malignant epithelial tumours and to improve their therapeutic management.