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Tumors of the Ear Canal
Diseases of the Ear Canal
0195-5616/88 $0.00 + .20
Tumors of the Ear Canal
Kenita S. Rogers, DVM, MS*
Tumors of the ear canal are relatively uncommon in the dog and cat compared with the overall incidence of integumentary neoplasms in these species. However, these tumors often represent a significant diagnostic and therapeutic challenge because they have typically been present for long periods of time before diagnosis. Ear disease in the small animal patient is usually recognized only when there are externally visible swellings, excessive irritation, abnormal discharges, deafness, or signs of vestibular disease. 6 In addition, the presence of a tumor is often overshadowed by clinical evidence of an associated chronic otitis externa. Tumors can arise from any of the structures lining or supporting the ear canal, including squamous epithelium, ceruminous or sebaceous glands, and mesenchymal tissues. The structures most often associated with neoplastic disease are the ceruminous glands of the external auditory canal and the squamous epithelium lining the external canal and the middle and inner ear cavities. Tumors arising from sebaceous glands or the osseous and cartilaginous skeleton of the canal are rare. Tumors of the external ear canal and meatus are far more common than those tumors originating in the middle or inner ear cavities, and generally have a much different clinical presentation. This article will describe the clinical presentation, diagnostic evaluation, expected biologic behavior, and therapeutic options for various tumors affecting the ear canal. In particular, the discussion will emphasize ceruminous gland neoplasia, squamous cell carcinoma, and non-neoplastic mass lesions. The less frequently reported tumors of the ear canal will be listed.
CLINICAL PRESENTATION The history of a patient with a tumor of the ear canal is often identical to that of any patient with chronic otitis externa. The physical presence of *Diplomate, American College of Veterinary Internal Medicine; Assistant Professor, Department of Small Animal Medicine and Surgery, Texas A&M University College of Veterinary Medicine, College Station, Texas Veterinary Clinics of North America: Small Animal Practice-Val. 18, No. 4, July 1988
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a tumor as an obstructive lesion favors the occurrence of otitis; thus, it is easy to understand why these patients are presented to the veterinarian for signs of infectious or inflammatory external ear disease. The client's complaints will be nonspecific and include a persistent otic discharge, head shaking, pawing at the ear, and an objectionable odor arising from the ears. Signs of otic disease may have been noted by the owners for weeks to years. The history of a chronic otitis externa that has not responded appropriately to therapy should prompt the clinician to perform a thorough otoscopic examination to determine if an underlying etiology (that is, neoplasia, non-neoplastic masses, or foreign bodies) is present. If clinical signs of vestibular disease are present, the history may include a gradual or acute onset of abnormalities. Neoplasia of the middle and inner ear must be differentiated from the more common causes of these clinical signs, including bacterial otitis media and interna, trauma, and idiopathic vestibular disorders. Bacterial and yeast infections are frequently associated with tumors of the ear canal. Two concepts should be considered. First, a secondary infection is common owing to the obstructive nature of the tumor, which results in impaired drainage and an accumulation of cerumen and debris. 23 Secondly, a cause-and-effect relationship has been theorized. The chronic irritation of underlying otitis externa may result in hyperplasia, dysplasia, and eventually neoplasia. Frequent episodes of unilateral or bilateral ear mite infestation are a common piece of historical information, particularly in cats with ceruminous gland adenocarcinoma. An eventual histologic change associated with chronic otitis externa is hyperplasia of the ceruminous glands, the most common structure associated with neoplasia of the ear canal. During physical examination, it is important to visualize the entire ear canal, including the tympanic membrane; this will require sedation or anesthesia in some animals. The examination may initially reveal evidence of obstructive disease with the mass visualized only after removal of the accumulated debris. The draining lymphatics and surrounding soft tissue should be palpated to detect metastatic sequelae or para-aural abscessation. Obstructive neoplasia of the ear canal may present as para-aural abscessation if the release of secretions and discharges through the normal meatus has been prevented. The suppurative material may break out of the ear canal into the surrounding soft tissue, with subsequent abscess formation in the parotid region. Para-aural abscessation has been reported in the dog and the cat. 12 Evidence of middle and inner ear involvement is signalled by signs of peripheral vestibular disease such as head tilt, ataxia, nystagmus, or Horner's syndrome. These patients often exhibit pain when opening the mouth. The appearance of the tympanic membrane may be altered; however, it is unusual for a mass originating in the middle ear to be visible on physical examination unless it has ruptured the membrane and is filling the external canal. The physical appearance of the tumors may vary. Small pedunculated masses are most typical of ceruminous gland hyperplasia, ceruminous gland adenoma, papillomas, and inflammatory polyps. Large infiltrative masses
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are more suggestive of ceruminous gland adenocarcinomas. Squamous cell carcinomas are generally ulcerated in appearance, particularly when involving the external canal and meatus. The masses vary greatly in their physical characteristics. They may be friable or firm, irregular in contour or smooth; they may be pedunculated or infiltrative into the wall of the canal and the surrounding soft tissue structures. They may be small and found incidentally, or may fill a significant portion of the canal, causing signs of obstructive disease. Bleeding is usually associated with ceruminous gland adenocarcinomas and squamous cell carcinomas. Tumors of the ear canal often cause an odor due to secondary infections or necrotic debris. Mter documenting the presence of the mass, it is imperative to evaluate the extent of disease as well as the nature of the lesion for the purpose of determining an accurate prognosis and defining therapeutic options.
EVALUATION OF THE PATIENT Evaluation of the patient with a tumor of the ear canal will vary with each individual case depending upon the extent of disease, the severity of clinical signs, and the overall health of the animal. A number of tests are available for the complete evaluation of the patient. An evaluation of any otic discharge is indicated to determine if secondary conditions such as yeast and bacterial infections are present. This is generally accomplished with direct otoscopic examination and cytologic evaluation of the exudate. This exudate is most often associated with secondary infection or tumor necrosis, and it is unusual to find cytologic evidence of neoplasia in this material. When evaluating the neoplastic mass, the most important diagnostic tools are the cytologic and histologic examination of a biopsy specimen. If the mass is visible externally or via an otoscope, biopsy may be accomplished with small alligator forceps or a snare. If the mass is deep within the ear canal and cannot be adequately visualized, a surgical procedure may be necessary to expose the tissue for biopsy. Appropriate surgical procedures are discussed in other articles in this issue. The accuracy of the histologic diagnosis will depend upon the experience of the pathologist and the adequacy of the sample. The advantages of histopathology over cytology for etiologic diagnosis include collection of a larger sample and maintenance of tissue architecture. Although histopathology is the definitive means of diagnosing a mass lesion, the value of cytology lies in the immediacy of diagnosis. Appropriate cytologic samples may be collected by several different methods. For masses of epithelial origin, aspiration cytology or impression smears are usually adequate. An exception to this would be in the case of squamous cell carcinoma. Although this tumor arises from epithelial tissue, it is generally ulcerative in appearance and the layer of tumor cells is very thin. Proper placement of a needle for aspiration of the tumor is therefore difficult. Impressions of this tumor usually yield only evidence of the inflammatory cells covering the ulceration. Thus, the best technique for collecting a diagnostic sample is a scraping. A
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scraping is also the technique of choice for collecting samples from mesenchymal tumors, because they do not exfoliate well on aspiration. After an appropriate cytologic sample has been collected, the initial step is to differentiate inflammatory from hyperplastic and neoplastic conditions. When inflammatory conditions are ruled out, the next step is to distinguish between neoplasms of epithelial and mesenchymal origin. Epithelial neoplasms exfoliate well and their cells are in clusters with cellto-cell adherence. The cells are predominantly round and have distinct cell membranes. Mesenchymal neoplasms generally exfoliate poorly with simple aspiration and must be scraped to acquire enough cells for evaluation. The cells exfoliate singly with indistinct cytoplasmic borders and tend to be spindle-shaped. The final cytologic step is to determine if the cells exhibit three or more malignant characteristics. These characteristics include differences in nuclear and nucleolar size, shape, and number; an increased nuclear to cytoplasmic ratio; cytoplasmic basophilia; and mitotic figures. If there are three or more strong malignant characteristics, the tumor is deemed malignant. Owing to the frequent presence of inflammatory changes, it is important for the cytologist to distinguish dysplastic cellular changes from neoplastic changes. If there are fewer than three malignant characteristics, the lesion may be hyperplastic, benign, or a well-differentiated malignancy. If malignancy is suspected, the patient should be evaluated for evidence of metastatic disease. The most likely sites of metastasis are the regional lymphatics and the lungs. Metastasis to distant viscera may occur. Palpation of the draining lymphatics may be helpful; those infiltrated with metastatic tumor are often very firm in consistency. Aspiration cytology or biopsy may be used to further evaluate for the presence of advanced disease. Macroscopic metastases may be detected with thoracic radiography. Patients with suspected disease of the middle and inner ear should receive a complete neurologic examination and skull radiographs. Neurologic signs may include ataxia, head tilt, nystagmus, and facial paralysis. The most helpful radiographs will be oblique and open-mouth views to outline the osseous bullae. Neoplasia may cause radiographic evidence of space-occupying masses, increased fluid density within the bullae, or osteolysis.
NEOPLASIA OF THE CERUMINOUS GLANDS Ceruminous glands are located in the deeper connective tissue layer of the ear canal. These coiled, tubular structures are modified apocrine sweat glands that, with the sebaceous glands, make cerumen. Some authors feel that these glands may be more numerous and better developed in the long-haired breeds than in the short-haired breeds, and suggest that longhaired breeds may be more susceptible to otitis and tumors of these glands. 6 • 23 In the normal ear, the thin, straight tubular secreting ducts of the ceruminous glands are usually difficult to distinguish. Ceruminous gland hyperplasia is frequently noted in chronically irritated ears. It is manifested
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by an increase in the size, distribution, and activity of the glands. Cystic dilatation of the glands and ducts can almost completely displace the sebaceous glands. 23 With chronicity of the lesion, the glands become dysplastic and predisposed to the development of neoplasia. Some investigators have suggested that chronic inflammation and the products of cerumen decomposition may be carcinogenic. 18 The ceruminous gland hyperplasia associated with chronic otitis externa is particularly prominent in the cat. 23 However, many ceruminous gland tumors occur spontaneously, with no evidence of an underlying cause. Authors disagree on whether ceruminous gland tumors are more prevalent in dogs or cats. 13· 15• 20 • 23 · 24 It is generally agreed that tumors arising from the ceruminous glands are usually found in middle-aged and older animals. Ceruminous gland tumors are rare, but they are the most common tumor found in the canine and feline external ear canal. 18 · 24 Adenomas are much more common than adenocarcinomas in the dog. 6 · 20 • 23 There is a much greater tendency for malignancy and aggressive biologic behavior in the cat than in the dog. As many as 50 per cent of cases in cats are malignant. 13 · 14• 1.s. 18 • 20 • 23 · 24 Ceruminous gland tumors account for l to 2 per cent of all feline tumors. 13 Because it is often difficult to distinguish clinically between hyperplastic, benign, and malignant disease of the ceruminous glands, cytology and histopathologic evaluation are necessary. Even with these methods, it is often difficult to distinguish between hyperplastic and benign changes. Ceruminous gland adenomas are the most common benign tumor of the ear canal, 4 • 20 and may develop secondary to chronic inflammation. 6 · 7 They arise usually from the external ear canal, but may originate from the inner surface of the lower portion of the pinna. The tumors are often pedunculated with a narrow or a wide stalk. They are typically irregular and multinodular in contour, and their consistency may be friable to firm. They are rarely invasive, but cause clinical signs compatible with otitis externa due to obstruction. Ceruminous gland adenocarcinomas are more frequently encountered in cats than in dogs, and are the most common malignant tumor of the ear canal in both species. The tumors arise primarily from within the external ear canal and may extend through the tympanic membrane into the middle ear. 19 They usually fill the external ear canal, and bleeding is commonly noted. Ceruminous gland adenocarcinomas tend to be locally invasive, both into the walls of the ear canal and into the soft tissue structures of the parotid region, 4 · 20 and may present as a para-aural abscess. The tumors tend to metastasize to regional lymphatics, lungs, and distant viscera. 5 · 6 • 13 · 15 • 20 • 24 It may be difficult to differentiate anaplastic ceruminous gland tumors from parotid gland carcinomas. Occasionally, a mixed ceruminous gland tumor is detected. 6 • 7 • 10• 20 Mixed tumors contain foci of myoepithelial cell proliferation or cartilage formation in addition to neoplasia of the ceruminous glands. Owing to the potentially fatal course of an adenocarcinoma, any mass in the external ear canal of an adult dog or cat should be biopsied for histologic evaluation. The treatment of choice for benign tumors or malignant tumors when there is no evidence of metastasis is complete surgical excision. 15 The
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appropriate surgical techniques are discussed in other articles in this issue. For malignant ceruminous gland tumors, ablation of the ear canal is usually not curative, and should be followed with external beam radiation therapy. 15 This form of local therapy may be helpful as an adjunctive measure for the treatment of a tumor that has not metastasized but is not completely resectable. At the present time, there is no published information describing the efficacy of various methods for treating tumors of the ceruminous glands in dogs and cats. Continued symptomatic medical care for secondary bacterial or mycotic infections is indicated.
SQUAMOUS CELL CARCINOMA Squamous cell carcinoma is a malignant tumor arising from the thin superficial epithelial lining of the pinna and ear canal. It is most frequently found on the pinna, but has been diagnosed in other locations within the ear canal. A thin layer of simple squamous epithelium lines the external auditory canal, the ventral portion of the tympanic cavity, auditory ossicles, the tympanic membrane, the membranes over the cochlear (round) and vestibular (oval) foramina, and the membranous labyrinth. 1· 6 Squamous cell carcinoma of the ear canal is considered rare, 9 but it is the most common neoplasm of the middle and inner ear cavities. It is also the most common malignant neoplasm involving the middle ear in man. 22 There have been five reports in the literature of cats with this tumor involving the middle ear and tympanic bullae. 6 · 9 • 16• 17• 22 One of the tumors also involved the external canal and surrounding tissue. 17 All cats had similar clinical presentations with evidence of damage to the seventh cranial nerve, manifested by combinations of facial paralysis, ataxia, head tilt, nystagmus, and Horner's syndrome. In addition, most of the cats showed pain on opening of the mouth, and several showed radiographic evidence of osteolysis. The tumor may metastasize via the regional lymphatics. Death is usually caused by intracranial extension of the neoplasm. 22 An associated side effect is the extension of a middle or inner ear infection to the meninges. Immediate surgical intervention is indicated if there is no evidence of metastasis. Radiation therapy can be helpful in controlling local disease but may not increase survival time. 22 Squamous cell carcinoma may also be found in the external ear canal, most commonly at the external auditory meatus. Tumors in this location may be locally invasive and metastasize via regional lymphatics, but they are generally more amenable to surgical excision and radiation therapy. Radiation is an effective modality of therapy for most squamous cell carcinomas of the head. 15
MISCELLANEOUS TUMORS OF THE EAR CANAL Tumors occasionally reported in the external ear canal of the cat include papillomas, 18 sebaceous gland tumors, 18 and a mast cell tumor at the auditory meatus. 4 The middle ear of the cat has been affected with a
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fibrosarcoma 17 and a lymphoma. 4 The inner ear has been secondarily invaded by a carcinoma of nasopharyngeal origin. 4 Papillomas and sebaceous gland adenomas were identified in the external ear canal of the dog. 23 The ear does not appear to be a site of metastasis of nonauricular malignancies. 13
NON-NEOPLASTIC MASS LESIONS Besides hyperplasia of the ceruminous glands, there are three nonneoplastic diseases that can mimic tumors of the ear cqnal. These conditions are of primary importance in cats, but are occasionally reported in dogs. 6 • 23 The most common of these conditions is the inflammatory polyp. 11 · 18 • 21 Several authors feel that polyps are the most commonly encountered growth in the ears of cats 4• 8 ; thus, it is important to differentiate them from malignant disease. They involve the middle ear and tympanic bullae more frequently than do neoplastic conditions. Inflammatory polyps occur at any age, with reported cases ranging from 3 months of age to 15 years. 4 There is no apparent sex or breed predisposition, and the condition is equal in occurrence on the right and left sides. The polyps may occur as a result of ascending infection from the nasopharynx or from prolonged infection of the middle ear. 3· 11 · 21 However, polyps were found in 6-month-old sibling kittens with no evidence of inflammation, suggesting a congenital origin. 21 They may be a sequela of an upper respiratory tract infection with subsequent otitis media, and may arise in the eustachian tube, tympanic cavity of the middle ear, or the nasopharynx. The polyps may lead to obstructive disease and cause rupture of the tympanic membrane with the mass evident in the external ear canal. Some polyps remain confined to the tympanic bullae. On occasion, the same type of polyp is found localized to the nasopharynx, originating in situ, or arising from the auditory tube, passing ventrally instead of into the bulla and middle ear. In most cases, the predominant clinical signs are related to the ears and include otic discharge, head shaking, head tilt, or the presence of a visible mass. If there is a large mass in the nasopharynx, the animal may present with respiratory compromise or dysphagia. 2 · 3 · 11 The polyps are generally pedunculated and are fixed by a thin stalk to their point of attachment, which is often the eustachian tube. They are usually smooth and occlude the ear canal, although they are not attached to the canal itself. 8 Polyps are characterized histologically by a mixed population of inflammatory cells, including neutrophils, macrophages, and plasma cells. They contain a variable number of lymphocytes. The polyps are covered by pseudostratified columnar ciliated respiratory epithelium that is continuous from the tympanic cavity to the eustachian tube and nasopharynx. Some polyps may be covered with squamous epithelium if the lesion originates in the deeper portion of the external ear canal. Inflammatory polyps may be differentiated from neoplasms by direct visualization, cytology, and histopathology. Skull radiographs may be helpful in showing a soft tissue mass in the pharyngeal region and within the bullae.
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Treatment of inflammatory polyps is usually uncomplicated. In most cases, the polyp can be grasped with forceps through the external meatus and gently removed with simple traction. A lateral ear resection may be helpful if the mass is not easily visualized. Traction is preferred to excision because it is more likely to remove the pedicle. 4• u If the mass is located primarily in the nasopharynx, the soft palate can be retracted to visualize the eustachian tube. Occasionally, it may be necessary to split the soft palate. If radiographs indicate that the tympanic bullae are involved, a bulla osteotomy may be required. A potential complication of this surgery is the development of temporary or permanent Horner's syndmme. 3 · 4 • 11 · 19 This problem occurs when the postganglionic sympathetic axons coursing through the middle .ear are damaged by curettage of the tympanic bullae. About one third of polyps recur after removal. 14 The presenting neurologic signs may take several weeks to improve or may never resolve completely. No beneficial effects have been noted with the use of topical or systemic corticosteroids for this inflammatory condition. 8 Another non-neoplastic condition that has been reported are cysts of the ceruminous glands. 4 · 18 Cats appear predisposed to this condition, and the cysts may occur at any age, with reports in patients from 2 to 15 years of age. The cysts are usually multiple and there may be bilateral involvement. These sessile masses are usually 0.1 to 0.5 em wide. They generally occur within the ear canal, but are occasionally found on the lower concave surface of the pinna. The third non-neoplastic condition is nodular hyperplasia of the sebaceous glands, reported in three cats. 4 Two of the masses were found within the ear canal and one was at the base of the pinna. Complete surgical excision is the treatment of choice for these conditions.
THERAPEUTIC CONSIDERATIONS The therapeutic measures of greatest benefit to patients with tumors of the ear canal are surgical excision and external beam radiation therapy. There are no standardized chemotherapy protocols in use in veterinary medicine because of the relatively low number of cases seen, and the even smaller number of malignant cases that warrant the use of chemotherapy. Continued symptomatic medical management is always indicated. This usually includes keeping the ears clean and dry, and treating for associated bacterial and yeast infections. There are several indications for surgical manipulation. First, an incisional or excisional biopsy may be required for diagnosis of the lesion. This may be accomplished with simple alligator forceps or may require a more advanced procedure for better visualization and manipulation of the mass. A lateral ear resection is indicated for better exposure and removal of masses confined to the external ear canal. Total ear canal ablation may be indicated for masses arising from the external ear canal that have infiltrated extensively into, or are adherent to, the walls of the canal with little extension into the soft tissues outside the canal. A bulla osteotomy is indicated for exposure and removal of masses of the middle and inner ear cavities. For predictable success of a surgical procedure, it is important to
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know the extent of the tumor. The surgeon should determine if the tumor is confined to the canal, has extended into the surrounding tissues, or has metastasized to distant locations. Radiation therapy may be a valuable therapeutic measure when tumors of the ear canal have been identified as squamous cell carcinoma or ceruminous gland neoplasia. The total dose of radiation delivered at the author's institution is 4800 cGy in 12 fractions. The success of therapy will depend upon the radiosensitivity of the individual tumor, the extent of disease, and the concomitant use of cytoreductive surgery. Combinations of surgery and radiation are used for these rare tumors in human beings. Further study will be necessary to determine the efficacy of these therapeutic measures for tumors of the ear canal in dogs and cats. REFERENCES l. Banks WJ: Eye and ear. In Banks WJ (ed): Applied Veterinary Histology. Baltimore, Williams & Wilkins, 1981, pp 532-539 2. Bedford PGC, Coulson A, Sharp NJH, et al: Nasopharyngeal polyps in the cat. Vet Rec
109:551, 1981 3. Bradley RL, Noone KE, Saunders GK, et al: Nasopharyngeal and middle ear polypoid masses in five cats. Vet Surg 14:141, 1985 4. Carpenter JL, Andrews LK, Holzworth J: Tumors and tumor-like lesions. In Holzworth J (ed): Diseases of the Cat. Philadelphia, WB Saunders Co, 1987, pp 565-569 5. Engle GC, Brodey RS: A retrospective study of 395 feline neoplasms. J Am Anim Hosp Assoc 5:21, 1965 6. Fraser G, Gregor WW, Mackenzie CP, et al: Canine ear diseases. J Small Anim Pract 10:725, 1970 7. Griffin CE: Otitis externa. Compend Contin Ed Pract Vet 3:741, 1981 8. Harvey CE, Goldschmidt MH: Inflammatory polypoid growths in the ear canal of cats. J Small Anim Pract 19:669, 1978 9. Indrieri RJ, Taylor RF: Vestibular dysfunction caused by squamous cell carcinoma involving the middle and inner ear in two cats. JAm Vet Med Assoc 184:471, 1984 10. Jabara AG: A mixed tumor and an adenoma both of ceruminous gland origin in a dog. Aust Vet J 52:590, 1976 11. Lane JG, Orr CM, Lucke VM, et al: Nasopharyngeal polyps arising in the middle ear of the cat. J Small Anim Pract 22:511, 1981 12. Lane JG, Watkins PE: Para-aural abscess in the dog and cat. J Small Anim Pract 27:521, 1986 13. Legendre AM, Krahwinkel OJ: Feline ear tumors. JAm Anim Hosp Assoc 17:1035, 1981 14. Macy OW, Seim HB: Medical and surgical aspects of the ear. Parts I and II. In Proceedings of the American Animal Hospital Association, 1985, pp 131-137 15. Madewell BR, Theilen GH: Tumors of the skin and subcutaneous tissues. In Theilen GH, Madewell BR (ed): Veterinary Cancer Medicine. Edition 2. Philadelphia, Lea & Febiger, 1987, p 259 16. PentlargeVW: Peripheral vestibular disease in a cat with middle and inner ear squamous cell carcinoma. Compend Contin Ed Pract Vet 6:731, 1984 17. Rendano VT, deLahunta A, King JM: Extracranial neoplasia with facial paralysis in two cats. J Am Anim Hosp Assoc 16:921, 1980 18. Scott OW: External ear disorders. J Am Anim Hosp Assoc 16:426, 1980 19. Smeak DO, Dehoff WD: Total ear canal ablation: Clinical results in the dog and cat. Vet Surg 15:161, 1986 20. Stannard AA, Pulley LT: Tumors of the skin and soft tissues. In Moulton JE (ed): Tumors in Domestic Animals. Edition 2. Berkeley, University of California Press, 1978, pp 5859 21. Stanton ME, Wheaton LG, Render JA, et al: Pharyngeal polyps in two feline siblings. J Am Vet Med Assoc 186:1311, 1985
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22. Stone EA, Goldschmidt MH, Littman MP: Squamous cell carcinoma of the middle ear in a cat. J Small Anim Pract 24:647, 1983 23. Van der Gaag I: The pathology of the external ear canal in dogs and cats. Vet Q 8:307, 1986 24. Woody BJ, Fox SM: Otitis externa: Seeing past the signs to discover the underlying cause. Vet Med 81:616, 1986 Department of Small Animal Medicine and Surgery College of Veterinary Medicine Texas A&M University College Station, Texas 77843
0195-5616/88 $0.00 + .20
Tumors of the Ear Canal
Kenita S. Rogers, DVM, MS*
Tumors of the ear canal are relatively uncommon in the dog and cat compared with the overall incidence of integumentary neoplasms in these species. However, these tumors often represent a significant diagnostic and therapeutic challenge because they have typically been present for long periods of time before diagnosis. Ear disease in the small animal patient is usually recognized only when there are externally visible swellings, excessive irritation, abnormal discharges, deafness, or signs of vestibular disease. 6 In addition, the presence of a tumor is often overshadowed by clinical evidence of an associated chronic otitis externa. Tumors can arise from any of the structures lining or supporting the ear canal, including squamous epithelium, ceruminous or sebaceous glands, and mesenchymal tissues. The structures most often associated with neoplastic disease are the ceruminous glands of the external auditory canal and the squamous epithelium lining the external canal and the middle and inner ear cavities. Tumors arising from sebaceous glands or the osseous and cartilaginous skeleton of the canal are rare. Tumors of the external ear canal and meatus are far more common than those tumors originating in the middle or inner ear cavities, and generally have a much different clinical presentation. This article will describe the clinical presentation, diagnostic evaluation, expected biologic behavior, and therapeutic options for various tumors affecting the ear canal. In particular, the discussion will emphasize ceruminous gland neoplasia, squamous cell carcinoma, and non-neoplastic mass lesions. The less frequently reported tumors of the ear canal will be listed.
CLINICAL PRESENTATION The history of a patient with a tumor of the ear canal is often identical to that of any patient with chronic otitis externa. The physical presence of *Diplomate, American College of Veterinary Internal Medicine; Assistant Professor, Department of Small Animal Medicine and Surgery, Texas A&M University College of Veterinary Medicine, College Station, Texas Veterinary Clinics of North America: Small Animal Practice-Val. 18, No. 4, July 1988
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a tumor as an obstructive lesion favors the occurrence of otitis; thus, it is easy to understand why these patients are presented to the veterinarian for signs of infectious or inflammatory external ear disease. The client's complaints will be nonspecific and include a persistent otic discharge, head shaking, pawing at the ear, and an objectionable odor arising from the ears. Signs of otic disease may have been noted by the owners for weeks to years. The history of a chronic otitis externa that has not responded appropriately to therapy should prompt the clinician to perform a thorough otoscopic examination to determine if an underlying etiology (that is, neoplasia, non-neoplastic masses, or foreign bodies) is present. If clinical signs of vestibular disease are present, the history may include a gradual or acute onset of abnormalities. Neoplasia of the middle and inner ear must be differentiated from the more common causes of these clinical signs, including bacterial otitis media and interna, trauma, and idiopathic vestibular disorders. Bacterial and yeast infections are frequently associated with tumors of the ear canal. Two concepts should be considered. First, a secondary infection is common owing to the obstructive nature of the tumor, which results in impaired drainage and an accumulation of cerumen and debris. 23 Secondly, a cause-and-effect relationship has been theorized. The chronic irritation of underlying otitis externa may result in hyperplasia, dysplasia, and eventually neoplasia. Frequent episodes of unilateral or bilateral ear mite infestation are a common piece of historical information, particularly in cats with ceruminous gland adenocarcinoma. An eventual histologic change associated with chronic otitis externa is hyperplasia of the ceruminous glands, the most common structure associated with neoplasia of the ear canal. During physical examination, it is important to visualize the entire ear canal, including the tympanic membrane; this will require sedation or anesthesia in some animals. The examination may initially reveal evidence of obstructive disease with the mass visualized only after removal of the accumulated debris. The draining lymphatics and surrounding soft tissue should be palpated to detect metastatic sequelae or para-aural abscessation. Obstructive neoplasia of the ear canal may present as para-aural abscessation if the release of secretions and discharges through the normal meatus has been prevented. The suppurative material may break out of the ear canal into the surrounding soft tissue, with subsequent abscess formation in the parotid region. Para-aural abscessation has been reported in the dog and the cat. 12 Evidence of middle and inner ear involvement is signalled by signs of peripheral vestibular disease such as head tilt, ataxia, nystagmus, or Horner's syndrome. These patients often exhibit pain when opening the mouth. The appearance of the tympanic membrane may be altered; however, it is unusual for a mass originating in the middle ear to be visible on physical examination unless it has ruptured the membrane and is filling the external canal. The physical appearance of the tumors may vary. Small pedunculated masses are most typical of ceruminous gland hyperplasia, ceruminous gland adenoma, papillomas, and inflammatory polyps. Large infiltrative masses
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are more suggestive of ceruminous gland adenocarcinomas. Squamous cell carcinomas are generally ulcerated in appearance, particularly when involving the external canal and meatus. The masses vary greatly in their physical characteristics. They may be friable or firm, irregular in contour or smooth; they may be pedunculated or infiltrative into the wall of the canal and the surrounding soft tissue structures. They may be small and found incidentally, or may fill a significant portion of the canal, causing signs of obstructive disease. Bleeding is usually associated with ceruminous gland adenocarcinomas and squamous cell carcinomas. Tumors of the ear canal often cause an odor due to secondary infections or necrotic debris. Mter documenting the presence of the mass, it is imperative to evaluate the extent of disease as well as the nature of the lesion for the purpose of determining an accurate prognosis and defining therapeutic options.
EVALUATION OF THE PATIENT Evaluation of the patient with a tumor of the ear canal will vary with each individual case depending upon the extent of disease, the severity of clinical signs, and the overall health of the animal. A number of tests are available for the complete evaluation of the patient. An evaluation of any otic discharge is indicated to determine if secondary conditions such as yeast and bacterial infections are present. This is generally accomplished with direct otoscopic examination and cytologic evaluation of the exudate. This exudate is most often associated with secondary infection or tumor necrosis, and it is unusual to find cytologic evidence of neoplasia in this material. When evaluating the neoplastic mass, the most important diagnostic tools are the cytologic and histologic examination of a biopsy specimen. If the mass is visible externally or via an otoscope, biopsy may be accomplished with small alligator forceps or a snare. If the mass is deep within the ear canal and cannot be adequately visualized, a surgical procedure may be necessary to expose the tissue for biopsy. Appropriate surgical procedures are discussed in other articles in this issue. The accuracy of the histologic diagnosis will depend upon the experience of the pathologist and the adequacy of the sample. The advantages of histopathology over cytology for etiologic diagnosis include collection of a larger sample and maintenance of tissue architecture. Although histopathology is the definitive means of diagnosing a mass lesion, the value of cytology lies in the immediacy of diagnosis. Appropriate cytologic samples may be collected by several different methods. For masses of epithelial origin, aspiration cytology or impression smears are usually adequate. An exception to this would be in the case of squamous cell carcinoma. Although this tumor arises from epithelial tissue, it is generally ulcerative in appearance and the layer of tumor cells is very thin. Proper placement of a needle for aspiration of the tumor is therefore difficult. Impressions of this tumor usually yield only evidence of the inflammatory cells covering the ulceration. Thus, the best technique for collecting a diagnostic sample is a scraping. A
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scraping is also the technique of choice for collecting samples from mesenchymal tumors, because they do not exfoliate well on aspiration. After an appropriate cytologic sample has been collected, the initial step is to differentiate inflammatory from hyperplastic and neoplastic conditions. When inflammatory conditions are ruled out, the next step is to distinguish between neoplasms of epithelial and mesenchymal origin. Epithelial neoplasms exfoliate well and their cells are in clusters with cellto-cell adherence. The cells are predominantly round and have distinct cell membranes. Mesenchymal neoplasms generally exfoliate poorly with simple aspiration and must be scraped to acquire enough cells for evaluation. The cells exfoliate singly with indistinct cytoplasmic borders and tend to be spindle-shaped. The final cytologic step is to determine if the cells exhibit three or more malignant characteristics. These characteristics include differences in nuclear and nucleolar size, shape, and number; an increased nuclear to cytoplasmic ratio; cytoplasmic basophilia; and mitotic figures. If there are three or more strong malignant characteristics, the tumor is deemed malignant. Owing to the frequent presence of inflammatory changes, it is important for the cytologist to distinguish dysplastic cellular changes from neoplastic changes. If there are fewer than three malignant characteristics, the lesion may be hyperplastic, benign, or a well-differentiated malignancy. If malignancy is suspected, the patient should be evaluated for evidence of metastatic disease. The most likely sites of metastasis are the regional lymphatics and the lungs. Metastasis to distant viscera may occur. Palpation of the draining lymphatics may be helpful; those infiltrated with metastatic tumor are often very firm in consistency. Aspiration cytology or biopsy may be used to further evaluate for the presence of advanced disease. Macroscopic metastases may be detected with thoracic radiography. Patients with suspected disease of the middle and inner ear should receive a complete neurologic examination and skull radiographs. Neurologic signs may include ataxia, head tilt, nystagmus, and facial paralysis. The most helpful radiographs will be oblique and open-mouth views to outline the osseous bullae. Neoplasia may cause radiographic evidence of space-occupying masses, increased fluid density within the bullae, or osteolysis.
NEOPLASIA OF THE CERUMINOUS GLANDS Ceruminous glands are located in the deeper connective tissue layer of the ear canal. These coiled, tubular structures are modified apocrine sweat glands that, with the sebaceous glands, make cerumen. Some authors feel that these glands may be more numerous and better developed in the long-haired breeds than in the short-haired breeds, and suggest that longhaired breeds may be more susceptible to otitis and tumors of these glands. 6 • 23 In the normal ear, the thin, straight tubular secreting ducts of the ceruminous glands are usually difficult to distinguish. Ceruminous gland hyperplasia is frequently noted in chronically irritated ears. It is manifested
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by an increase in the size, distribution, and activity of the glands. Cystic dilatation of the glands and ducts can almost completely displace the sebaceous glands. 23 With chronicity of the lesion, the glands become dysplastic and predisposed to the development of neoplasia. Some investigators have suggested that chronic inflammation and the products of cerumen decomposition may be carcinogenic. 18 The ceruminous gland hyperplasia associated with chronic otitis externa is particularly prominent in the cat. 23 However, many ceruminous gland tumors occur spontaneously, with no evidence of an underlying cause. Authors disagree on whether ceruminous gland tumors are more prevalent in dogs or cats. 13· 15• 20 • 23 · 24 It is generally agreed that tumors arising from the ceruminous glands are usually found in middle-aged and older animals. Ceruminous gland tumors are rare, but they are the most common tumor found in the canine and feline external ear canal. 18 · 24 Adenomas are much more common than adenocarcinomas in the dog. 6 · 20 • 23 There is a much greater tendency for malignancy and aggressive biologic behavior in the cat than in the dog. As many as 50 per cent of cases in cats are malignant. 13 · 14• 1.s. 18 • 20 • 23 · 24 Ceruminous gland tumors account for l to 2 per cent of all feline tumors. 13 Because it is often difficult to distinguish clinically between hyperplastic, benign, and malignant disease of the ceruminous glands, cytology and histopathologic evaluation are necessary. Even with these methods, it is often difficult to distinguish between hyperplastic and benign changes. Ceruminous gland adenomas are the most common benign tumor of the ear canal, 4 • 20 and may develop secondary to chronic inflammation. 6 · 7 They arise usually from the external ear canal, but may originate from the inner surface of the lower portion of the pinna. The tumors are often pedunculated with a narrow or a wide stalk. They are typically irregular and multinodular in contour, and their consistency may be friable to firm. They are rarely invasive, but cause clinical signs compatible with otitis externa due to obstruction. Ceruminous gland adenocarcinomas are more frequently encountered in cats than in dogs, and are the most common malignant tumor of the ear canal in both species. The tumors arise primarily from within the external ear canal and may extend through the tympanic membrane into the middle ear. 19 They usually fill the external ear canal, and bleeding is commonly noted. Ceruminous gland adenocarcinomas tend to be locally invasive, both into the walls of the ear canal and into the soft tissue structures of the parotid region, 4 · 20 and may present as a para-aural abscess. The tumors tend to metastasize to regional lymphatics, lungs, and distant viscera. 5 · 6 • 13 · 15 • 20 • 24 It may be difficult to differentiate anaplastic ceruminous gland tumors from parotid gland carcinomas. Occasionally, a mixed ceruminous gland tumor is detected. 6 • 7 • 10• 20 Mixed tumors contain foci of myoepithelial cell proliferation or cartilage formation in addition to neoplasia of the ceruminous glands. Owing to the potentially fatal course of an adenocarcinoma, any mass in the external ear canal of an adult dog or cat should be biopsied for histologic evaluation. The treatment of choice for benign tumors or malignant tumors when there is no evidence of metastasis is complete surgical excision. 15 The
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appropriate surgical techniques are discussed in other articles in this issue. For malignant ceruminous gland tumors, ablation of the ear canal is usually not curative, and should be followed with external beam radiation therapy. 15 This form of local therapy may be helpful as an adjunctive measure for the treatment of a tumor that has not metastasized but is not completely resectable. At the present time, there is no published information describing the efficacy of various methods for treating tumors of the ceruminous glands in dogs and cats. Continued symptomatic medical care for secondary bacterial or mycotic infections is indicated.
SQUAMOUS CELL CARCINOMA Squamous cell carcinoma is a malignant tumor arising from the thin superficial epithelial lining of the pinna and ear canal. It is most frequently found on the pinna, but has been diagnosed in other locations within the ear canal. A thin layer of simple squamous epithelium lines the external auditory canal, the ventral portion of the tympanic cavity, auditory ossicles, the tympanic membrane, the membranes over the cochlear (round) and vestibular (oval) foramina, and the membranous labyrinth. 1· 6 Squamous cell carcinoma of the ear canal is considered rare, 9 but it is the most common neoplasm of the middle and inner ear cavities. It is also the most common malignant neoplasm involving the middle ear in man. 22 There have been five reports in the literature of cats with this tumor involving the middle ear and tympanic bullae. 6 · 9 • 16• 17• 22 One of the tumors also involved the external canal and surrounding tissue. 17 All cats had similar clinical presentations with evidence of damage to the seventh cranial nerve, manifested by combinations of facial paralysis, ataxia, head tilt, nystagmus, and Horner's syndrome. In addition, most of the cats showed pain on opening of the mouth, and several showed radiographic evidence of osteolysis. The tumor may metastasize via the regional lymphatics. Death is usually caused by intracranial extension of the neoplasm. 22 An associated side effect is the extension of a middle or inner ear infection to the meninges. Immediate surgical intervention is indicated if there is no evidence of metastasis. Radiation therapy can be helpful in controlling local disease but may not increase survival time. 22 Squamous cell carcinoma may also be found in the external ear canal, most commonly at the external auditory meatus. Tumors in this location may be locally invasive and metastasize via regional lymphatics, but they are generally more amenable to surgical excision and radiation therapy. Radiation is an effective modality of therapy for most squamous cell carcinomas of the head. 15
MISCELLANEOUS TUMORS OF THE EAR CANAL Tumors occasionally reported in the external ear canal of the cat include papillomas, 18 sebaceous gland tumors, 18 and a mast cell tumor at the auditory meatus. 4 The middle ear of the cat has been affected with a
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fibrosarcoma 17 and a lymphoma. 4 The inner ear has been secondarily invaded by a carcinoma of nasopharyngeal origin. 4 Papillomas and sebaceous gland adenomas were identified in the external ear canal of the dog. 23 The ear does not appear to be a site of metastasis of nonauricular malignancies. 13
NON-NEOPLASTIC MASS LESIONS Besides hyperplasia of the ceruminous glands, there are three nonneoplastic diseases that can mimic tumors of the ear cqnal. These conditions are of primary importance in cats, but are occasionally reported in dogs. 6 • 23 The most common of these conditions is the inflammatory polyp. 11 · 18 • 21 Several authors feel that polyps are the most commonly encountered growth in the ears of cats 4• 8 ; thus, it is important to differentiate them from malignant disease. They involve the middle ear and tympanic bullae more frequently than do neoplastic conditions. Inflammatory polyps occur at any age, with reported cases ranging from 3 months of age to 15 years. 4 There is no apparent sex or breed predisposition, and the condition is equal in occurrence on the right and left sides. The polyps may occur as a result of ascending infection from the nasopharynx or from prolonged infection of the middle ear. 3· 11 · 21 However, polyps were found in 6-month-old sibling kittens with no evidence of inflammation, suggesting a congenital origin. 21 They may be a sequela of an upper respiratory tract infection with subsequent otitis media, and may arise in the eustachian tube, tympanic cavity of the middle ear, or the nasopharynx. The polyps may lead to obstructive disease and cause rupture of the tympanic membrane with the mass evident in the external ear canal. Some polyps remain confined to the tympanic bullae. On occasion, the same type of polyp is found localized to the nasopharynx, originating in situ, or arising from the auditory tube, passing ventrally instead of into the bulla and middle ear. In most cases, the predominant clinical signs are related to the ears and include otic discharge, head shaking, head tilt, or the presence of a visible mass. If there is a large mass in the nasopharynx, the animal may present with respiratory compromise or dysphagia. 2 · 3 · 11 The polyps are generally pedunculated and are fixed by a thin stalk to their point of attachment, which is often the eustachian tube. They are usually smooth and occlude the ear canal, although they are not attached to the canal itself. 8 Polyps are characterized histologically by a mixed population of inflammatory cells, including neutrophils, macrophages, and plasma cells. They contain a variable number of lymphocytes. The polyps are covered by pseudostratified columnar ciliated respiratory epithelium that is continuous from the tympanic cavity to the eustachian tube and nasopharynx. Some polyps may be covered with squamous epithelium if the lesion originates in the deeper portion of the external ear canal. Inflammatory polyps may be differentiated from neoplasms by direct visualization, cytology, and histopathology. Skull radiographs may be helpful in showing a soft tissue mass in the pharyngeal region and within the bullae.
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Treatment of inflammatory polyps is usually uncomplicated. In most cases, the polyp can be grasped with forceps through the external meatus and gently removed with simple traction. A lateral ear resection may be helpful if the mass is not easily visualized. Traction is preferred to excision because it is more likely to remove the pedicle. 4• u If the mass is located primarily in the nasopharynx, the soft palate can be retracted to visualize the eustachian tube. Occasionally, it may be necessary to split the soft palate. If radiographs indicate that the tympanic bullae are involved, a bulla osteotomy may be required. A potential complication of this surgery is the development of temporary or permanent Horner's syndmme. 3 · 4 • 11 · 19 This problem occurs when the postganglionic sympathetic axons coursing through the middle .ear are damaged by curettage of the tympanic bullae. About one third of polyps recur after removal. 14 The presenting neurologic signs may take several weeks to improve or may never resolve completely. No beneficial effects have been noted with the use of topical or systemic corticosteroids for this inflammatory condition. 8 Another non-neoplastic condition that has been reported are cysts of the ceruminous glands. 4 · 18 Cats appear predisposed to this condition, and the cysts may occur at any age, with reports in patients from 2 to 15 years of age. The cysts are usually multiple and there may be bilateral involvement. These sessile masses are usually 0.1 to 0.5 em wide. They generally occur within the ear canal, but are occasionally found on the lower concave surface of the pinna. The third non-neoplastic condition is nodular hyperplasia of the sebaceous glands, reported in three cats. 4 Two of the masses were found within the ear canal and one was at the base of the pinna. Complete surgical excision is the treatment of choice for these conditions.
THERAPEUTIC CONSIDERATIONS The therapeutic measures of greatest benefit to patients with tumors of the ear canal are surgical excision and external beam radiation therapy. There are no standardized chemotherapy protocols in use in veterinary medicine because of the relatively low number of cases seen, and the even smaller number of malignant cases that warrant the use of chemotherapy. Continued symptomatic medical management is always indicated. This usually includes keeping the ears clean and dry, and treating for associated bacterial and yeast infections. There are several indications for surgical manipulation. First, an incisional or excisional biopsy may be required for diagnosis of the lesion. This may be accomplished with simple alligator forceps or may require a more advanced procedure for better visualization and manipulation of the mass. A lateral ear resection is indicated for better exposure and removal of masses confined to the external ear canal. Total ear canal ablation may be indicated for masses arising from the external ear canal that have infiltrated extensively into, or are adherent to, the walls of the canal with little extension into the soft tissues outside the canal. A bulla osteotomy is indicated for exposure and removal of masses of the middle and inner ear cavities. For predictable success of a surgical procedure, it is important to
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know the extent of the tumor. The surgeon should determine if the tumor is confined to the canal, has extended into the surrounding tissues, or has metastasized to distant locations. Radiation therapy may be a valuable therapeutic measure when tumors of the ear canal have been identified as squamous cell carcinoma or ceruminous gland neoplasia. The total dose of radiation delivered at the author's institution is 4800 cGy in 12 fractions. The success of therapy will depend upon the radiosensitivity of the individual tumor, the extent of disease, and the concomitant use of cytoreductive surgery. Combinations of surgery and radiation are used for these rare tumors in human beings. Further study will be necessary to determine the efficacy of these therapeutic measures for tumors of the ear canal in dogs and cats. REFERENCES l. Banks WJ: Eye and ear. In Banks WJ (ed): Applied Veterinary Histology. Baltimore, Williams & Wilkins, 1981, pp 532-539 2. Bedford PGC, Coulson A, Sharp NJH, et al: Nasopharyngeal polyps in the cat. Vet Rec
109:551, 1981 3. Bradley RL, Noone KE, Saunders GK, et al: Nasopharyngeal and middle ear polypoid masses in five cats. Vet Surg 14:141, 1985 4. Carpenter JL, Andrews LK, Holzworth J: Tumors and tumor-like lesions. In Holzworth J (ed): Diseases of the Cat. Philadelphia, WB Saunders Co, 1987, pp 565-569 5. Engle GC, Brodey RS: A retrospective study of 395 feline neoplasms. J Am Anim Hosp Assoc 5:21, 1965 6. Fraser G, Gregor WW, Mackenzie CP, et al: Canine ear diseases. J Small Anim Pract 10:725, 1970 7. Griffin CE: Otitis externa. Compend Contin Ed Pract Vet 3:741, 1981 8. Harvey CE, Goldschmidt MH: Inflammatory polypoid growths in the ear canal of cats. J Small Anim Pract 19:669, 1978 9. Indrieri RJ, Taylor RF: Vestibular dysfunction caused by squamous cell carcinoma involving the middle and inner ear in two cats. JAm Vet Med Assoc 184:471, 1984 10. Jabara AG: A mixed tumor and an adenoma both of ceruminous gland origin in a dog. Aust Vet J 52:590, 1976 11. Lane JG, Orr CM, Lucke VM, et al: Nasopharyngeal polyps arising in the middle ear of the cat. J Small Anim Pract 22:511, 1981 12. Lane JG, Watkins PE: Para-aural abscess in the dog and cat. J Small Anim Pract 27:521, 1986 13. Legendre AM, Krahwinkel OJ: Feline ear tumors. JAm Anim Hosp Assoc 17:1035, 1981 14. Macy OW, Seim HB: Medical and surgical aspects of the ear. Parts I and II. In Proceedings of the American Animal Hospital Association, 1985, pp 131-137 15. Madewell BR, Theilen GH: Tumors of the skin and subcutaneous tissues. In Theilen GH, Madewell BR (ed): Veterinary Cancer Medicine. Edition 2. Philadelphia, Lea & Febiger, 1987, p 259 16. PentlargeVW: Peripheral vestibular disease in a cat with middle and inner ear squamous cell carcinoma. Compend Contin Ed Pract Vet 6:731, 1984 17. Rendano VT, deLahunta A, King JM: Extracranial neoplasia with facial paralysis in two cats. J Am Anim Hosp Assoc 16:921, 1980 18. Scott OW: External ear disorders. J Am Anim Hosp Assoc 16:426, 1980 19. Smeak DO, Dehoff WD: Total ear canal ablation: Clinical results in the dog and cat. Vet Surg 15:161, 1986 20. Stannard AA, Pulley LT: Tumors of the skin and soft tissues. In Moulton JE (ed): Tumors in Domestic Animals. Edition 2. Berkeley, University of California Press, 1978, pp 5859 21. Stanton ME, Wheaton LG, Render JA, et al: Pharyngeal polyps in two feline siblings. J Am Vet Med Assoc 186:1311, 1985
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22. Stone EA, Goldschmidt MH, Littman MP: Squamous cell carcinoma of the middle ear in a cat. J Small Anim Pract 24:647, 1983 23. Van der Gaag I: The pathology of the external ear canal in dogs and cats. Vet Q 8:307, 1986 24. Woody BJ, Fox SM: Otitis externa: Seeing past the signs to discover the underlying cause. Vet Med 81:616, 1986 Department of Small Animal Medicine and Surgery College of Veterinary Medicine Texas A&M University College Station, Texas 77843