Actinic keratosis is a common disease in humans, which also affects dogs. Lesions occur in chronically sun exposed areas, such as flank, ventral and lateral abdomen. It has been reported that actinic keratosis is a pre-neoplastic disease which may evolve into squamous cell carcinoma (SCC), which is one of the most frequent malignant neoplasm in dogs. The aim of this research was to investigate the relationship between COX-2 and cell proliferation on the outcome of dogs with actinic keratosis

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... ctinic keratosis and cutaneous squamous cell carcinoma. This study included 10 skin sections of actinic keratosis (G1) and 10 cutaneous SCC (G2). Data including age, breed, gender and histopathological findings were documented. Paraffin-embedded tissues were retrieved for COX-2 and Ki-67 staining. American Pit Bull Terrier dogs were the most affected ones in both G1 and G2, the mean age was 4.3 (±0.8) years and 5.6 (±1.7) years, respectively. Mean score of COX-2 immunostaining in G1 and G2 was 8.16 (±3.51) and 8.56 (±1.03), respectively. Mean percentage of immunopositive cells for Ki-67 in G1 and G2 was 15.77 (±8.81) and 17.71 (±12.21), respectively. There was no association between COX-2 expression and Ki-67, recurrence, survival and metastasis rate (p > 0.05). These findings highlight the role of COX-2 and Ki-67 in carcinogenesis, but do not confirm the relationship between COX-2 expression and increased cell proliferation in dogs. COX-2 may play a role in carcinogenesis, but this pathway is not responsible for cellular proliferation in actinic keratosis and cutaneous SCC in dogs. Both markers were not useful tools to differentiate the outcome of affected dogs.