In this study, we investigate the histological changes and alterations in mRNA levels of key factors relevant to cancer and stem cells (Oct4, Sox2, and Nanog) [14], angiogenesis and key aspects of tumorigenesis (VEGF 188) [15], inflammation (COX–2) [16,17], and keratinocyte differentiation (Keratin 10) [18,19,20] in canine skin tissue for 9 weeks following irradiation with a clinically applied therapeutic dose of radiation. This evidence concerns the gene PTGS2 and cancer.