Auricular Non-Epithelial Tumors with Solar Elastosis in Cats: A Possible UV-Induced Pathogenesis

Abstract

The photoinduced etiopathology of actinic keratosis and squamous cell carcinoma in feline species is well known. This etiology has also been reported for non-epithelial cutaneous tumors in other species. To date, no cases of auricular non-epithelial cutaneous neoplasms erased in a contest of actinic keratosis in cats have been reported. The aim of this study was to describe feline auricular non-epithelial cutaneous neoplasms associated with typical UV-induced cutaneous lesions and solar elastosis. The study was conducted on five feline cases diagnosed with auricular non-epithelial cutaneous tumors (two fibrosarcomas, one mixosarcoma, one epithelioid melanoma and one hemangiosarcoma), selected from the Tumor Registry of the Department of Veterinary Sciences of the University of Pisa (1998-2018). Ten and six feline auricular biopsies of normal skin and skin with actinic keratosis, respectively, were used as controls. Orcein stain was used to investigate solar elastosis. Histological changes related to chronic solar irradiation were documented in the skin adjacent to the neoplastic lesions in the five cats. Considering the anatomical localization and the results of histopathology, this study suggests that non-epithelial cutaneous neoplasms may have a UV-induced etiopathogenesis in the feline species.

Keywords: UV light; auricular; cats; elastosis; neoplasms; solar.

Figure 1

Auricular pinna, cat. (A) Fibrosarcoma. Hyperplastic epidermis with stratification disorder and dermal fibrosis in tissues adjacent to the neoplasm. HE. Bar = 50 µm. (B) Fibrosarcoma. Superficial dermis adjacent to the neoplasm with a considerable amount of elastic fibers. Insert: Higher magnification of hypertrophic, fragmented, branched or elastic fibers arranged in a dense cluster around a glandular structure. Orcein staining. Bar = 50 µm. (C) Epithelioid melanoma. Normal configuration of the epidermis at the periphery of the tumor. HE. Bar = 50 µm. (D) Epithelioid melanoma. Superficial dermis adjacent to the neoplasm with a moderate amount of hypertrophic elastic fibers. Insert: Higher magnification of hypertrophic, fragmented and tangled elastic fibers. Orcein staining. Bar = 50 µm. (E) Control group 1. Epidermal hyperplasia with increasing dermal collagen in horizontal arrangement and hypertrophic elastic fibers. Presence of a sunburn cell with pyknotic nuclei and a strong eosinophilic cytoplasm (arrow). HE. Bar = 200 µm. (F) Control group 1. Superficial dermis containing hypertrophic, branched, tangled elastic fibers. Orcein staining. Bar = 200 µm. (G) Control group 2. Normal configuration of the epidermis and dermis. HE. Bar = 100 µm. (H) Control group 2. Superficial dermis containing thin, regular elastic fibers oriented parallel to the dermal-epidermal junction. Orcein staining. Bar = 100 µm.