Occurrence of Cutaneous Neoplasia in Dogs with Actinic Dermatitis in a Veterinary Medical Teaching Hospital - UFRGS, Brazil

Abstract

Background: Actinic dermatitis is an environmental skin disease resulting from excessive exposure to ultraviolet light irradiated by the sun. This phototoxic reaction affects dogs and cats, particularly with short hair and lightly pigmented skin, exposed to sun light. Primary lesions are typical from a sunburn and chronic exposure, and may induce to a premalignant lesion known as actinic keratosis, which may develop to neoplasms. The aim of the present study was to describe a retrospective study of actinic dermatitis and the occurrence of cutaneous neoplasia in dogs presented to a Veterinary Medical Teaching Hospital (HCV/UFRGS) in Porto Alegre, Rio Grande do Sul, Brazil in a period of 10 years.Materials, Methods & Results: A retrospective review of medical records from January 2009 to December 2019 was performed to identify dogs with actinic dermatitis. Twenty-eight dogs were diagnosed based on a history of sun exposure and skin lesions including erythema, scaling, comedones, thickened skin, hyperpigmentation, ulceration and/or secondary infections on poorly pigmented skin. In addition, in twelve dogs (42.8%) the disease was also confirmed by histopathology. Cutaneous lesions locations were previously defined as head, limbs, neck and trunk. The head was subdivided in chin, ears, face, lips and nasal plane; the limbs in pelvic and thoracic; and the trunk, in abdomen, dorsal pelvis, perianal and thorax. All 28 dogs diagnosed with actinic dermatitis in the study had been chronically exposed to solar radiation and had light skin and coat. Dogs were between 3 and 20 years old, mean 7.6 years and median 7 years, mostly female dogs (64.2%) and neutered or spayed (64.2%). The most affected breeds were American Pitbull Terrier (35.7%) and Boxers (28.5%). Other breeds were Bull Terrier, Dalmatian, Dogo Argentino and Scottish Terrier. In 15 cases, tumors were confirmed by cytopathology or histopathology, resulting in 9 different skin tumors and two types of cysts (epidermoid and follicular). Among these, the most prevalent malignant neoplasm was squamous cell carcinoma (66.7%), followed by mast cell tumor (40%), hemangiosarcoma (26.6%), and basal cell carcinoma (6.6%). Five benign tumors were identified: hemangioma (13.3%), fibroma (6.6%), lipoma (6.6%), sebaceous adenoma (6.6%) and trichoepithelioma (6.6%). The most prevalent location for actinic lesions was the trunk (92.8%), being more prevalent on the ventral abdomen (82.1%). Actinic lesions were also present on head, neck and limbs. In 13/15 patients (86.6%), actinic lesions and at least one neoplasia location matched.Discussion: Actinic dermatitis tends to occurs in mid-aged to senile dogs because of the disease progressive and chronic behavior and owners delay to detect early clinical signs. In fact, actinic dermatitis was diagnosed at the average age of 7.6 years in the present study. The skin lesions were mostly located on light hair areas and were not observed on pigmented skin. The trunk (mainly the abdomen) had higher frequency of skin lesions compared to other anatomic areas, possibly because some dogs like to sunbathe at dorsal or lateral recumbency, some floor types can reflect sunlight, and some ventral abdomen are hairless. Ultraviolet radiation causes important local and systemic immunogenic changes. The impairment of the immune system and antigen recognition can influence cutaneous susceptibility to develop neoplasm. In conclusion, approximately 50% of the dogs with actinic dermatitis were associated with different skin neoplasm. The most prevalent was squamous cell carcinoma, mast cell tumor and hemangiosarcoma. Actinic lesions and neoplasm matched location in almost all patients with both conditions, however it was not possible to define if solar radiation had predisposed the occurrence of all observed neoplasms. Further studies are needed to prove the influence of ultraviolet radiation in the development of different cutaneous neoplasms.

Prevalence and anatomopathological characterization of cutaneous squamous cell carcinomas with regional and distant metastases in dogs and cats: 20 cases (1985–2020)

“…1,5 Also, due to the habit of enjoying sunbathing in the supine or lateral position of the dogs, it was expected to find a greater number of cases with actinic alterations in the SCCs in the abdominal region. 5,26 However, evidence of actinic lesions, the location of tumours in the head and abdomen and the high level of solar radiation in the geographical location of the animals in this study suggest that ultraviolet radiation played a significant role in the pathogenesis. Prolonged exposure to solar radiation causes changes in the DNA of epidermal keratinocytes, causing progressive epithelial modifications, which, if successful during the replication phases, will become permanent and initiate the formation of a malignant tumour.…”

“…This data was overestimated, mainly due to the abdominal location of the vast majority of tumours, together with the fact that the animals in this study are located in a geographic location that provides long periods of incidence of sunlight and a wide climate variety, which favours the development of SCC of solar origin 1,5 . Also, due to the habit of enjoying sunbathing in the supine or lateral position of the dogs, it was expected to find a greater number of cases with actinic alterations in the SCCs in the abdominal region 5,26 . However, evidence of actinic lesions, the location of tumours in the head and abdomen and the high level of solar radiation in the geographical location of the animals in this study suggest that ultraviolet radiation played a significant role in the pathogenesis.…”

Molecular Profile of Canine Hemangiosarcoma and Potential Novel Therapeutic Targets

“…HSA may arise in any region of the body, especially the skin, spleen, liver and atrium [ 2 , 3 ]. Skin lesions can be multiple, often small and related to ultraviolet radiation (UV) and actinic damage, especially in the lower abdomen of dogs with white or thin hair coats [ 4 , 5 ]. However, HSA may also occur in the subcutis, muscle and visceral organs.…”

“…HSA has a variable breed predisposition. Whereas dermal neoplasia seems to be directly caused by UV exposure in white dog breeds, especially in Pitbull Terrier and Boxer [ 4 , 5 ], the visceral forms are overrepresented in breeds such as Golden Retriever, Labrador Retriever, German Shepherd and Miniature Schnauzer [ 3 , 7 , 8 , 12 , 13 , 14 ].…”

“…The prognosis for actinic cutaneous lesions is favorable and surgery is usually curative with long survival rates [ 25 , 26 ]. Nevertheless, aggressive systemic forms of disease are associated with poor prognosis with a median survival time (MST) of 23–292 days [ 4 , 25 , 26 , 27 ].…”