Case Report

Bilateral Pinnal Squamous Cell Carcinoma in a Dog with Chronic Otitis Externa

WILLIAM H. MILLER, Jr. & KEVIN J. SHANLEY

Department of Clinical Studies, School of Veterinary Medicine,

University of Pennsylvania, Philadelphia, U.S.A.

Veterinary Dermatology 1991; 2: 37-39

Abstract- An aged dog with a chronic, bilateral, bacterial otitis externa developed bilateral squamous cell carcinomas of the pinna. .The tumours were located where the pinna would cover the external auditory meatus and probably were induced by the chronic infection.

Key Words: Dog; Skin; Otitis externa; Squamous cell carcinoma.

INTRODUCTION

Squamous cell carcinomas (SCC) are common tu- mours in the dog, and in most instances, the tumours develop for no apparent reason ( I ) . In human be- ings, many different skin disorders can predispose to the development of skin tumours in damaged skin (2-4). In the dog, apart from some documented cases of solar-induced SCC (5), little is known of the factors inducing SCC. The purpose of this report is to describe a dog which developed SCC on the inner surface of each pinna in apparent response to chronic, bilateral, bacterial otitis externa.

Case Report An 1 1-year old male, mongrel dog was presented with a chronic ear disorder. The dog had suffered from ear disease for approximately 10 years but the owner had made no real attempt to treat the dog.

On physical examination, the dog had bilateral, exudative, proliferative otitis externa. The inner sur- face of each pinna was erythematous and on each pinna, a proliferative, ulcerated mass, approximately 2.5. cm in diameter, was present in the area where the pinna would cover the external auditory meatus (Fig. 1). The painful and proliferative nature of the otitis externa precluded a complete otoscopic exami- nation. The diagnosis of chronic bacterial otitis was made on the physical findings. The pinnal masses

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Correspondence to William H. Miller, Jr. New York State College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, U.S.A. Copyright European Society of Veterinary Dermatology.

were thought to be either areas of pyogranulomatous inflammation or neoplasms. The dog was discharged and the owner instructed to administer chloram- phenicol orally (55 mg.kg-' every 8 h) and to apply topical cupramyxin (Unitop, Roche, Nutley, N.J., USA) twice daily to both ears.

The dog was re-examined 2 weeks later and the otitis externa was much improved, but the pinnal masses were unchanged. Biopsy samples were taken from each mass and the histological diagnosis was bilateral squamous cell carcinoma. The dog's ears were treated by bilateral pinnal amputation and lateral ear resection. Post-surgical healing was un- complicated.

Figure 1. Ulcerative, proliferative squamous cell carcinoma of the right pinna.

38 William H. Miller. Jr. and Kevin J. Shanley

Approximately 2 years after surgery, the dog was presented with a large, ulcerated mass in the right prescapular region. The mass had been present for at least four months and was enlarging. Over the same time, the dog’s appetite had decreased and he had become lethargic. On examination, the dog had pro- liferative, exudative otitis of the remaining ear canals, a 6 x 1.5 cm ulcerated mass in the right cervical skin and enlargement of the right prescapular lymph node. Because of the dog’s poor health, the owner elected to have him euthanised. At necropsy, the skin mass was found to be a pyogranulomatous cellulitis. The draining lymph node showed reactive hyperplasia. No neoplastic cells were seen in either tissue.

DISCUSSION

SCC are locally invasive, malignant neoplasms, aris- ing from squamous epithelial cells. In human beings, it is felt that most develop in response to some cutaneous insult. The most well-known predisposing factor is prolonged solar exposure but SCC also have been associated with exposure to various environmen- tal or medical carcinogens, ionizing radiation, scars from burns, frostbite or trauma, various erosive or scarring dermatoses, anatomical malformations, or chronic skin infections (2-4). When SCC arises in damaged skin, a co-carcinogen, such as ultraviolet light, may be necessary to induce the malignant transformation (4). SCC arising in damaged skin in human beings have a much higher metastatic rate than those associated with prolonged solar exposure ( 6 ) . SCC are common tumours in all domestic species except the pig (1, 7, 8). Their association with solar exposure in fair- skinned cats and farm animals is well-known (1, 7). Dogs with normal skin appear to be resistant to the damaging effects of ultraviolet light in that prolonged, enhanced exposure to intense solar radiation is required to induce SCC (5 ) . Pre-existing skin damage may sensitize the skin to solar damage in that dogs with post-inflammatory nasal depigmen- tation and cats with labial indolent ulcers can develop SCC in the damaged skin (1,9). Cutaneous SCC have developed in the dog at the injection site of a live papilloma virus vaccine (10) and in scars in the dog and horse (8, 1 1 - 13). The authors are unaware of any reports associating SCC in animals with chronic infections.

The reasons why SCC can develop in damaged skin are unknown. In humans, the latent period between skin damage and SCC is very long, typically 20 years or longer (4). During this time, the damaged skin can be exposed to a variety of secondary insults which may act as co-carcinogens.

The tumours in the dog of this report most proba- bly were direct sequelae to the chronic bacterial infection of the ears. The location of the tumours coincided with the area of the pinna which would cover the external auditory meatus. In this location,

the pinnal skin would not be exposed to ultraviolet light but would be in constant contact with the discharge from the ear. Because the owner had done little to treat the ear infections, drug induction of the tumours can be discounted. Whether the bacteria, bacterial products, otic debris or some combination thereof acted as the inciting factor( s) is not known.

From the paucity of reports of SCC arising in damaged skin of animals, the process would appear to be rare and probably relates to the shorter life span of domestic animals. Damaged skin should be pro- tected from exposure to known or potential carcino- gens and any lesions which develop in the area should be evaluated carefully.

REFERENCES

1. Muller, G. H., Kirk, R. W., Scott, D. W. Small Animal Dermatology. 4th ed. Philadelphia: W. B. Saunders 1989: 854-7.

2. Stoll, H. L., Schwartz, R. A. Squamous cell car- cinoma! In: Fitzpatrick, T. B., Eisen, A. Z., Wolff, K., Freedberg, I . M., Austen, K. F., eds. Dermatology in general medicine. 3rd ed. New York: McGraw-Hill, 1987: 746-58.

3 . Patterson, J. W. Squamous cell carcinoma. In: Demis, D. J., ed. Clinical dermatology. Vo1.4. Philadelphia: Harper and Row, 1988; unit 21-21: 1-16.

4. Kaplan, R. P. Cancer complicating chronic ulcerative and scarifying mucocutaneous disorders. In: Callen, J. P., Dahl, M. V., Golitz, L. E., Rasmussen, J. E., Stegman, S. J., eds. Advances in dermatology. Vol. 2. Chicago: Year Book Medical Publishers, 1987: 19-71.

5. Hargis, A. M., Thomassen, R. W. Solar keratosis (solar dermatosis, senile keratosis) and solar keratosis with squamous cell carcinoma. American Journal of Pathology 1979; 94: 193-6.

6. Lever, W. F., Schaumburg-Lever, G. Histopathology of the skin. 6th ed. Philadelphia: J. B. Lippincott,

7. Scott, D. W. Large animal dermatology. Philadelphia: W. B. Saunders, 1988: 429-31.

8. Theilen, G. H., Madewell, B. R. Veterinary cancer medicine. 2nd ed. Philadelphia: Lea and Febiger, 1987: 240- 53.

9. Scott, D. W. Feline dermatology 1900-1978: a mono- graph. Journal of the American Animal Hospital As- sociation 1980; 16: 406- 18.

10. Sundberg, J. P., Junge R. E., Lancaster, W. D. Im- munoperoxidase localization of papilloma viruses in hyperplastic and neoplastic epithelial lesions of ani- mals. American Journal of Veterinary Research 1984;

11 . Gourley, I . M., Madewell, B. R., Barr, B., Ettinger, S. J. Burn scar malignancy in a dog. Journal of the American Veterinary Medical Association 1982; 180: 1095-7.

12. Schumacher, J., Watkins, J. P., Wilson, S. R., Fore- man, M. E. Burn-induced neoplasia in two horses. Equine Veterinary Journal 1986; 18: 410-2.

13. Baird, A. N., Frelier, P. F. Squamous cell carcinoma originating from an epithelial scar in a horse. Journal of the American Veterinary Medical Association 1990;

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Squamous cell carcinoma 39

Resume-Un chien age souffrant d’otite externe bacterienne chronique bilaterale presenta un epithelioma spinocellulaire bilateral des pavillons auriculaires. Les tumeurs Ctaient situees la ou les pavillons auraient recourvert le meat auriculaire et furent sans doute provoques par I’infection chronique. [Miller, W. H., Shanley, K. J., Bilateral pinnal squamous cell carcinoma in a dog with chronic otitis extrena (Epithelioma spino-cellulaire bilateral des pavillons auriculaires chez chien souffrant d’otite externe chronique). Veterinary Dermatology 1991; 2 37-39].

Zusammenfassung-Ein alter Hund mit einer chronischen, bilateralen, bakteriell bedingten Otitis externa entwickelte Plattenepithelkarzinome en beiden Ohrmuscheln. Diese Tumore traten an der Pinna exakt an der Miindung des iuReren Gehorgangs auf, und sind moglicherweise durch die chronische Infektion induziert worden. [Miller, H. W. Jr., Shanley, K . J . Bilateral pinnal squamous cell carcinoma in a dog with chronic otitis externa (Bilaterale Plattenepithelkarzinome bei einem Hund mit chronischer Otitis externa). Veterinary Dermatology, 1991; 2: 37-39].

Resumen-Un perro de edad avanzada que presentaba una otitis externa bilateral bacteriana cronica desarrollo unos carcinomas de celulas escamosas bilaterales del pabellon auditivo. Los tumores estaban localizados en la entrada del meato auditivo y probablemente fueron inducidos por la infeccion cronica. [Miller, W. H. Jr., Shanley, K. J. Bilateral pinnal squamous cell carcinoma in a dog with a chronic otitis externa (Carcinoma de celulas escamosas bilaterales en 10s pabellones auditivos de un perro con otitis externa cronica). Veterinary Dematology, 1991; 2: 37-39].

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