Skin Photodamage Lesions in a Bilateral Feline Auricular Primary Fibrosarcoma

SIMPLE SUMMARY: Recent studies suggest a photoinduced etiopathology not only for actinic keratosis and squamous cell carcinomas, but also for non-epithelial cutaneous tumors in feline species. We report a recent case of a ten-year-old male cat with a white-hair coat and mesenchymal neoplasms of both auricles. Cytology, complete blood count (CBC), serum biochemistry and imaging examinations were performed. After surgery, the samples underwent routinary histopathology and special staining with orcein. A routine analysis yielded values within a normal range and X-rays and ultrasonography showed no abnormalities. The cytology was inconclusive, but, through histopathology, two well-differentiated fibrosarcomas were diagnosed and histopathological changes related to chronic UV exposure were documented in the skin close to the lesions. An orcein stain highlighted elastosis, the hallmark of photodamage; a morphometric analysis showed that the elastotic material was more abundant in the dermis close to the tumors. Therefore, an involvement of UV rays in the carcinogenic process of these tumors may be suspected. ABSTRACT: As with human species, recent studies also suggest a photoinduced etiopathology for non-epithelial cutaneous tumors in feline species. We report a recent case of a ten-year-old male cat with a white-hair coat and mesenchymal neoplasms of both auricles. Cytology, complete blood count (CBC), serum biochemistry and imaging examinations were performed. After surgery, the samples underwent routinary histopathology and were additionally stained with orcein. A routine analysis yielded values within a normal range and the imaging examination showed no abnormalities, suggesting that the bilateral presentation of neoplasms was primary rather than metastatic. The cytology was inconclusive, but, through histopathology, two well-differentiated fibrosarcomas were diagnosed and histopathological changes related to chronic UV exposure (such as epidermal hyperplasia, stratification disorders, keratinocyte dysplasia and an accumulation of elastotic material) were documented in the skin adjacent to the lesions. An orcein stain succeeded in highlighting elastosis. The elastic fibers lost their regular structure and orientation and appeared to be fragmented, wavy to branched and knotted. A morphometric analysis showed that the amount of elastotic material in the dermis close to the tumors was more than double compared with the more distant areas. Elastosis is considered to be a hallmark of photodamage; thus, an involvement of UV rays in the carcinogenic process of the tumors may be suspected.