Cholesteatomas are epidermoid cysts (aggregations of keratinized squamous debris) that can expand in the middle ear in dogs. They have been very rarely reported in cats (1, 2).
Etiology and Pathophysiology of Cholesteatomas in Small Animals
A cholesteatoma is a keratinized, stratified, squamous epithelium–lined cyst filled with squamous debris. These tumors can be locally destructive, can lead to secondary inflammation, and can induce secondary otitis externa or otitis media.
Although the pathogenesis of cholesteatomas is not completely understood, they can be associated with eustachian tube dysfunction (leading to tympanic membrane invagination), can occur secondary to chronic otitis media, or can be secondary to surgery of the ear canal and middle ear.
Cholesteatomas can be locally destructive, causing lysis, sclerosis, and proliferation of the tympanic bulla. The bulla can also expand and be filled with soft tissue.
Epidemiology of Cholesteatomas in Small Animals
Cholesteatomas occur most commonly in dogs but have been reported in cats. There is no pronounced breed predilection associated with cholesteatomas. The age of affected patients varies.
Clinical Findings of Cholesteatomas in Small Animals
Clinical signs of cholesteatomas often include those associated with otitis externa and otitis media (head shaking, pain on palpation of ear/bulla or opening of the mouth, exudate in the external ear canal, facial nerve palsy).
In chronic cases, a cholesteatoma might not be visible on otic examination, owing to stenosis, exudate, and chronic changes. When visible, the tumor is frequently pearly white and protrudes from the middle ear to the external ear canal, with the tympanic membrane ruptured.
Cholesteatomas warrant complete neurological examination focusing on dysfunction of the facial nerve.
Diagnosis of Cholesteatomas in Small Animals
Radiography, CT, and MRI
Histological examination
Diagnosis of cholesteatomas is based on advanced imaging to assess changes to the middle ear (see CT scan image). Bulla radiography can be performed if neither CT nor MRI is available; however, radiographs do not provide as much information.
Courtesy of Dr. Michelle Woodward.
When possible, samples of the mass should be submitted for cytological and histological examination to confirm the type of lesion present (see cytological image).
Courtesy of Dr. Shannon Dehghanpir.
Because of the potential for secondary infection with cholesteatomas, culture of the middle or external ear should also be considered, depending on the results of cytological examination.
Treatment of Cholesteatomas in Small Animals
Surgery
Treatment of secondary infections
Corticosteroids for inflammation
Surgical treatment of cholesteatoma can be curative; however, recurrence after surgery is common. If possible, surgery should be done early in the disease to limit tumor expansion. Even in later-stage disease, however, surgery can be palliative.
Bulla osteotomy or total ear canal ablation with bulla osteotomy should be considered. As much diseased tissue as possible should be removed.
Medical management of cholesteatomas can include treatment of secondary infections and administration of corticosteroids (systemic and topical) to decrease inflammation.
Key Points
Cholesteatomas are benign epidermoid cysts.
Advanced imaging is needed for diagnosis.
Surgical treatment can be curative.
For More Information
Risselada M. Diagnosis and management of cholesteatomas in dogs. Vet Clin North Am Small Anim Pract. 2016;46:623-634.
Imai A, Kondo H, Suganuma T, Nagata M. Clinical analysis and nonsurgical management of 11 dogs with aural cholesteatoma. Vet Dermatol. 2019;30(1):42-e12.
Also see pet owner content regarding tumors of the ear canal in dogs and cats.
References
Alexander A, Mahoney P, Scurrell E, Baines S. Cholesteatoma in a cat. JFMS Open Rep. 2019;5(1):2055116919848086. doi:10.1177/2055116919848086
Terao M, Uemura T, Hasegawa H, et al. Case report: intracranial epidermoid cyst in a cat. Front Vet Sci. 2024;11:1426421. doi:10.3389/fvets.2024.1426421
