Chronic dermatosis and cutaneous squamous cell carcinoma in the beagle dog

Heat Tolerance of Siberian Husky Dogs Living in Brazil: A Case Study on the Perceptions and Attitudes of Their Owners

The management of the thermal environment to which dogs are exposed should be included in strategies to improve their welfare. An online questionnaire was administered to 624 owners of Siberian Husky dogs residing in Brazil, with the objective of assessing their perceptions regarding their dogs' capacity to adapt to heat, and its association with the owners' routine care. Owners who believed that dogs are low-heat-tolerant animals were more likely to report heat response behaviors from their dogs. Overall, owners reported walk with their dogs during early morning, late afternoon and nighttime. They also reported solar radiation as the primary criteria for determining the time to walk with their dogs. However, owners who reported walking with their dogs at noon mentioned time availability as their primary criteria. In conclusion, owners perceive Siberian Husky dogs living in Brazil as being poorly adapted to heat, and this perception appeared to influence their positive attitudes towards protecting their dogs from heat stress by choosing to walk them during times with less solar exposure. However, the lack of time for owners to walk with their dogs during cooler periods can still be a risk factor in exposing the animals to extreme hot conditions.

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

The aim of this study was to assess the prevalence of regional and distant metastases from cutaneous squamous cell carcinomas (SCCs) in dogs (n = 11) and cats (n = 9) in a retrospective case series over 36 years (1985-2020), as well as to characterize its macroscopic aspects (location and size), degree of differentiation (well, moderately and poorly differentiated [WD, MD and PD, respectively]) and the rate of cell proliferation, by counting the AgNORs. Immunohistochemistry (IHC) was used to identify patterns of tumour migration and invasion (islands, ribbons, cords, small aggregates, individual cells [fusiform and amoeboid]) and to evaluate the intensity of desmoplasia and the amount of myofibroblasts. The prevalence of metastatic SCCs was 4.39% (21/478), being 3.8% in dog (12/309) and 5.3% in cat (9/169). Metastases affected lymph nodes in all dogs and 66% (6/9) of cats, and less frequently distant organs. Primary tumours predominantly affected the abdominal skin in dogs and the nasal planum in cats. Among the 20 cases, 52% were MDs, 34% were WDs, and 14% were PDs. Histological lesions suggestive of exposure to chronic solar radiation were present in 57% (8/14). The main patterns of tumour migration and invasion were islands for WD SCCs and individual cells for PD SCCs. MD SCCs had a mix of patterns. In cats, individual spindle cells were restricted to PDs. A marked desmoplastic reaction was more associated with PD SCCs and often with MDs. This study highlights that the prevalence of SCC metastases in dogs and cats is predominantly regional. The IHC was essential in the identification of individual fusiform keratinocytes, whose presence in surgical margins may represent a greater risk of recurrence. Although the presence of myofibroblasts was observed in all infiltrative and metastatic tumours, further studies evaluating these cells may be important to better understand their role in the tumour microenvironment of cutaneous SCCs with metastasis in dogs and cats.

Mutations of p53 gene in canine sweat gland carcinomas probably associated with UV radiation

Introduction

Apocrine sweat gland carcinomas (ASGCs) are rare malignant skin tumours in dogs and humans. The literature published so far focuses mostly on the clinico-epidemiological aspect of these tumours, but little is known about their pathogenesis. In this study we aimed to determine whether the p53 gene is involved in the carcinogenesis of the apocrine sweat gland in dogs and whether ultraviolet radiation (UV) is related to it.

Material and Methods

Forty canine ASGCs were submitted to laser capture microdissection to isolate neoplastic cells, from which DNA was subsequently extracted. PCR amplification and sequencing of p53 exons 2–8 was then performed, followed by computer analysis of the obtained sequences.

Results

Sixteen mutations within the p53 gene were found in 13 tumours. The mutations involved C → T, T → C, G → A, and CC → TT transitions, C → G transversion and adenine deletion, which are gene alteration types known to be related to UV radiation in the process of skin carcinogenesis in humans. Six of the thirteen tumour cases displayed the C → T transitions in the same location in exon 4 and three of the thirteen cases displayed T → C in the same location in exon 5.

Conclusion

The results of the present study indicate both the participation of the p53 gene and the influence of UV radiation in the formation of ASGCs in dogs.

Clinical features and outcome of dermal squamous cell carcinoma in 193 dogs (1987-2017)

Squamous cell carcinoma (SCC) is a frequently recognized dermal tumour in dogs and has been described as a common pathology induced by solar ultraviolet radiation exposure. Little has been published about this neoplasm with regard to clinical features and outcome in dogs. This retrospective study included 193 dogs from a single institution histopathologically diagnosed with SCC of the dermis. Thirty-eight percent of all dogs had documented histopathologic actinic change. The overall median survival time was 1004 days, with the population demonstrating actinic change associated with a significantly longer survival time (median 1359 days, range 16-3530 days) compared to dogs without actinic change (median 680 days, range 16-3066 days) and this achieved significance on multivariate analysis (hazard ratio 0.42, 95% confidence interval 0.193-0.930, P = 0.032). These data demonstrate increased survival of dogs with SCC demonstrating actinic change over those with non-actinic SCCs, and purports long-term survival for these animals. Dogs received a variety of treatment approaches as a retrospective study, and future prospective studies will be necessary to investigate whether adjunct therapies such as radiation or chemotherapy offer improvement in survival for dermal SCC in the dog.

Melanin granules melanophages and a fully-melanized epidermis are common traits of odontocete and mysticete cetaceans

BACKGROUND

The cellular mechanisms used to counteract or limit damage caused by exposure of marine vertebrates to solar ultraviolet (UV) radiation are poorly understood. Cetaceans are vulnerable because they lack protective skin appendages and are obliged to surface continuously to breathe, thus being exposed repeatedly to UV light. Although molecular mechanisms of photoprotection of cetaceans have been studied, there is limited knowledge about their epidermal structure and photoprotective effectors.

OBJECTIVE

To describe and compare the epidermis of mysticete and odontocete cetaceans and identify potentially photoprotective traits.

ANIMALS

Twenty eight free-living individuals belonging to six cetacean species were sampled in the Mexican Central Pacific and Gulf of California. Species sampled were the bottlenose dolphin, pantropical spotted dolphin, spinner dolphin, Bryde's whale, fin whale and humpback whale.

METHODS

Histological and cytological evaluation of skin biopsy tissue collected in the field between 2014 and 2016.

RESULTS

All cetaceans had only three epidermal layers, lacking both the stratum granulosum and stratum lucidum. A relatively thick stratum corneum with a parakeratosis-like morphology was noted. Melanin was observed within keratinocytes in all epidermal layers, including the stratum corneum and apical melanin granules obscured the keratinocyte nucleus. Keratinocytes had a perinuclear halo. Keratinocyte diameter differed between cetacean suborders and amongst species. Melanophage clusters were common in most cetacean species.

CONCLUSIONS

The widespread presence of melanin and the unexpectedly high number of melanophages may constitute a unique photoprotective trait of cetaceans and could reflect primitive adaptations to their environment and to their obligate marine-bound life.

Immunohistochemical analysis of ocular hemangiomas and hemangiosarcomas in dogs

PURPOSE

To determine if molecular markers typically associated with ultraviolet exposure could be detected in canine ocular hemangiomas (HA) and hemangiosarcomas (HSA).

METHODS

Paraffin-embedded samples of canine ocular HA (n = 6) and HSA (n = 6) were examined for the presence of p53, p21, p16, cyclin D, PCNA, pAkt, telomerase, and estrogen receptor (ER)-alpha using immunohistochemistry.

RESULTS

p53 and cyclin D protein were not detected in any of the canine HA or HSA samples. The majority of the HA and HSA were negative for both p21 and telomerase. pAkt immunoreactivity was absent in one HA, one HSA, but was present in five HA and five HSA. All of the HA or HSA samples were strongly positive for p16 and PCNA. ERalpha was expressed in all of the samples examined; there was more intense staining in the HSA samples compared to the HA samples.

CONCLUSIONS

Results from this study describe the protein expression, via immunohistochemistry, that might be altered in UV exposure in HA and HAS formation. p53 may not play an important role in tumor development; rather, in the tumors examined, expression of cell cycle regulators independent of the p53 pathway appear central in HA and HSA formation and progression. In addition, this study finds that ERalpha may be involved in promoting the invasive behavior associated with HSA.

Photodamage in feline skin: clinical and histomorphometric analysis

The purpose of this study was to investigate clinical and histomorphometric features of cat skin under long-term solar exposure. Ear skin of 34 Domestic Shorthair cats that were chronically exposed to sun was classified as follows: group 0, normal (n = 13); group 1, initial stage of photodamage (PD) (n = 10); group 2, advanced stage of PD (n = 11). Histologic sections were examined independently by 2 pathologists, and epidermal thickness, adnexal unit area, and dermal cellularity were assessed by morphometry. A positive correlation was obtained between age, degree of edema and sclerosis in the upper dermis, telangiectases, squamatization of basal keratinocytes, and epidermis thickness and the degree of PD. The area occupied by adnexal structures in the dermis diminished with increased PD. Dermal sclerosis and edema best separated the 3 groups. The results indicated a high level of skin hypersensitivity to sun rays in cats. The findings may be useful for clinical testing and in general veterinary pathology and dermatology.

Squamous cell carcinoma of the nasal planum in 17 dogs

Squamous cell carcinoma of the nasal planum was diagnosed in 17 dogs over a period of 11 years. Ulceration, bleeding and sneezing were the most common clinical signs. One dog had cytological evidence of metastasis to the local lymph node. The dogs were treated by surgical resection, fractionated megavoltage irradiation, or a combination of the two. Surgical resection gave the most favourable results; four of six dogs were cured but a recurrence of the tumour was predicted in the other two on the basis of incomplete or marginal resection. Radiotherapy alone was not as effective; one of four dogs was cured, and the tumour recurred in the others within 24 weeks (median eight weeks). Combined surgical resection and radiotherapy did not produce a cure in any of the seven remaining dogs, and the tumour recurred within 12 weeks (median nine weeks). Three dogs had cytological evidence of lymph node metastasis when the tumour recurred. The dogs' prognosis was adversely affected by the interval between their initial examination and treatment, but there was no apparent association between the histological grade of the tumour and the clinical outcome.

Ovine squamous cell carcinoma: immunocharacterisation of neoplastic cells and peritumoural cellular infiltrate

An immunohistochemical characterisation of neoplastic cells and peritumoural cellular infiltrate of ovine squamous cell carcinomas (OSCC) in different stages of growth was carried out using a commercially-available panel of seven antibodies, and formalin-fixed and paraffin-embedded tissue samples. Neoplastic cells reacted with the anti-keratin monoclonal antibody RCK-102 and with an anti-keratin polyclonal antibody, whereas they were unreactive with the anti-keratin monoclonal antibody NCL-5D3. The tumour cells were unreactive with the anti-vimentin polyclonal antibody. Increased numbers of CD3+ T-lymphocytes, IgG-containing plasma cells and lysozyme+ macrophages were associated with precancerous lesions (actinic keratosis) and with early OSCC. These results show that early lesions of OSCC induce an in situ cellular and humoral immune response. In advanced OSCC, the number of CD3+ T-lymphocytes and macrophages in the peri- and intratumoural cellular infiltrate remained high, whereas a significant decrease of IgG-containing plasma cells was found compared with early OSCC. This finding suggests an in situ decrease in the humoral immune response in advanced OSCC.

Dorsal skin reactions to sunlight and artificial ultraviolet light in hairless descendants of Mexican hairless dogs

Dorsal skin reactions to irradiation with two different types of ultraviolet (UV) light sources (sunlight and artificial UV light) were investigated in hairless descendants of Mexican hairless dogs. The total energy dose of solar UV exposure and artificial UV irradiation was 90 kJ/m2 and 40 kJ/m2, respectively. Histological examinations were done up to 7 days after UV irradiation (7 DAI). At 1 DAI, the solar UV-exposed skin did not show marked changes, while artificial UV irradiated skin exhibited a visible erythematous reaction and prominent histological alterations such as epidermal thickening, appearance of sunburn cells and deformation elastic fibers. At 4 DAI of solar UV-exposure, the skin color became moderately dark and noticeable pigmentation developed in the epidermis. In contrast, at 4 DAI of artificial UV irradiation, there still remained moderate degeneration in the epidermis and dermis, and delayed tanning was weak. At 7 DAI of solar exposure, delayed suntan reactions became more prominent. Histologically, there were heavy pigmentation of melanin granules mainly in the stratum basale. On the other hand, artificial UV irradiated skin showed less pigmentation. Thus, solar exposure provoked remarkable pigmentation while artificial UV irradiation brought about severe sunburn reactions in the dorsal skin of hairless dogs.

Clinical evaluation of etretinate for the treatment of canine solar-induced squamous cell carcinoma and preneoplastic lesions

BACKGROUND

Tumors of the skin and subcutaneous tissue account for 30% of all canine neoplasms. Canine solar-induced squamous cell carcinoma (SCC) is the most frequently reported canine cutaneous neoplasm.

OBJECTIVE

The purpose of this study was to provide preliminary observations on the safety and efficacy of etretinate for the treatment of solar-induced SCC and associated preneoplastic lesions in dogs.

METHODS

Etretinate was administered to 10 dogs at 1 mg/kg twice daily for a minimum of 90 days.

RESULTS

Clinically, two dogs showed complete resolution of their preneoplastic lesions, three dogs had partial responses, two dogs maintained stable disease, and three dogs showed progression of lesions after 90 days of etretinate administration. Three dogs showed histologic improvement, four dogs showed no changes, and three dogs showed evidence of progressing SCC. Treatment-related biochemical abnormalities included reversible hypertriglyceridemia and transient serum liver enzyme elevations in three dogs.

CONCLUSION

These preliminary findings suggest that etretinate, at the dosage administered, may provide therapeutic efficacy for solar-induced preneoplastic lesions in the dog, particularly for those multifocal lesions not easily managed by local methods of therapy.

A retrospective clinicopathologic study of 212 dogs with cutaneous hemangiomas and hemangiosarcomas

The relationship between skin pigmentation and piliation and the development of hemangiomas and hemangiosarcomas in the dermis and subcutaneous tissue was studied in 212 dogs. These 212 dogs had a combined total of 306 tumors; 38 of these 212 dogs had two or more of the same tumor in a different location or a combination of hemangioma and hemangiosarcoma. The average age of the dogs at the time of excision of these tumors was greater than 10 years. There was no sex predilection for the presence or absence of tumors. Cutaneous hemangiomas (73%) were more common than cutaneous hemangiosarcomas (27%). Hemangiomas had no predilection for dermis (51%) or subcutaneous tissue (47%), but hemangiosarcomas had a marked predilection for dermis (73%) over subcutaneous tissue (7%). Dogs with short hair coats and lightly pigmented skin had more hemangiomas and hemangiosarcomas of the dermis (65%) than did dogs with variable length hair coats and pigmentation (28%). Dogs with short hair coats and lightly pigmented skin had fewer hemangiomas and hemangiosarcomas of the subcutaneous tissue (10%) than did dogs with variable length hair coats and pigmentation (22%). Dogs with short hair coats and lightly pigmented skin also had more hemangiomas and hemangiosarcomas of ventral glabrous skin (65%) than did dogs with variable length hair coats and pigmentation (22%). In addition, there was no predilection of subcutaneous hemangiosarcoma for haired (33%) versus glabrous (33%) skin, but dermal hemangiosarcoma had a marked predilection for the glabrous skin (63%) when compared with haired skin (10%). The increased incidence of dermal hemangiomas and hemangiosarcomas in ventral glabrous skin suggests an association between solar radiation and the biologic properties of glabrous skin in the genesis of these tumors.

Synthetic retinoids in veterinary dermatology

The synthetic retinoids, isotretinoin (Accutane) and etretinate (Tegison) are vitamin A analogs. They affect epithelial differentiation and thus have potential for therapy for disorders of epithelial maturation such as keratinization defects of cutaneous neoplasia. The pharmacology, indications for use, clinical experience, potential toxicities, and recommended monitoring of these drugs are discussed.

Squamous cell carcinoma in a puppy

A tumour diagnosed histologically as a squamous cell carcinoma occurred in the umbilical region of a 4-month-old female mongrel puppy. The tumour was removed by cryosurgery. There has been no recurrence for nearly 3 years.

Sunscreens promote repair of ultraviolet radiation-induced dermal damage

Chronic UV irradiation profoundly damages the dermis of human and animal skin. These alterations were thought to be irreversible. Recently, we showed that substantial repair occurred in hairless mice after stopping UV exposure. A band of new connective tissue was laid down subepidermally. The present study focussed on whether repair would occur if animals were protected by sunscreens after dermal damage was induced and irradiation was continued. Albino hairless mice were exposed to Westinghouse FS20 sunlamps thrice weekly for 30 weeks. The daily dose of UV (UVB + UVA) was 0.17 J/cm2. Sunscreens of sun protection factors (SPF) 6 and 15 were applied after 10 and 20 weeks of irradiation. Biopsies were taken at 10, 20, 30, and 45 weeks of the experiment. With both sunscreens, especially SPF-15, previously damaged dermis was repaired during continued irradiation. Repair occurred in situ and, in severely damaged skin, in the novel form of subepidermal reconstruction zones of new connective tissue with parallel collagen bundles and a network of fine elastic fibers.

Prevention of ultraviolet damage to the dermis of hairless mice by sunscreens

To assess the ability of sunscreens to protect connective tissue from actinic damage, hairless mice were irradiated with Westinghouse FS20 sunlamps thrice weekly for 30 weeks. Each exposure, consisting mainly of UV-B and the less energetic UV-A, was approximately 6 human minimal erythema doses under these lights. One group of animals received irradiation only. The other 2 groups were treated, prior to irradiation, with sunscreens of either low or high sun protection factors (SPF 2 and SPF 15, respectively). Skin biopsies were taken at 10-week intervals and were stained with various histochemical stains to reveal changes in the dermis. The unprotected, irradiated animals showed a great increase in the following: reticulin fibers, elastic fibers to the extent of elastosis, neutral and acid mucopolysaccharides and melanin production. The SPF 15 sunscreen completely prevented these changes. The SPF 2 sunscreen was less effective. These effects were substantiated by ultrastructural examination of the tissues by electron microscopy. A surprising histologic finding was the repair capability of the dermis in the post-irradiation period.

Sunlight-skin cancer association in the dog: a report of three cases

Squamous cell carcinoma is one of the most frequently recognized neoplastic diseases of the canine integument, although few risk factors influencing tumor development have been clearly defined. Three dogs with cutaneous squamous cell carcinomas are reported. Tumors developed in lightly-pigmented, glabrous following chronic sunlight exposure and long period of dermatosis. Microscopic examination of tissues from the three dogs showed progressive development of epithelial hyperplasia through stages of solar keratosis-like lesions to invasive and metastatic squamous cell carcinoma.