Immunohistochemical expression of COX-2 in normal. hyperplastic and neoplastic canine lymphoid tissues

There is much interest in the potential use of cyclooxygenase-2 (COX-2) selective inhibitors in combination with other cancer therapeutics. COX-2 is a key-role enzyme in prostaglandin synthesis and has been implicated in the pathogenesis of numerous canine and feline malignancies. There is little data on the potential role of COX-2 in canine lymphoma pathogenesis. To investigate the presence of COX-2 over-expression in canine normal, hyperplastic and neoplastic lymphatic tissues, 80 canine lymph node tissue samples (12 from non-pathologically enlarged normal lymph nodes, 24 from lymph node hyperplasias and 44 from lymphomas, 22 B-cell and 22 T-cell lymphomas) have been evaluated by immunohistochemistry to determine the enzyme expression. Scoring was performed according to previous studies and tissues scoring +2 and +3 were recorded as overexpressing. In hyperplastic lymph node tissues only a few macrophages were COX-2 positive, while six out of the 44 examined lymphomas (13.6%; 3 B- and 3 T-cell lymphomas) were COX-2 overexpressing. This is the first study describing COX-2 immunoreactivity neoplastic lymph nodes tissues. Even if a wider number of samples needs to be investigated to draw some firmer conclusions, these data suggest a rationale for further investigate COX-2 expression in these neoplasms for prognostic, chemopreventive and chemotherapic implications.