Malignant Ear Tumors in Cats: Contrasting Literature

By Brooke Simon, DVM
angell.org/dermatology
dermatology@angell.org
617-524-5733

March 2024

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Introduction

Tumors within the ear canals of cats are uncommon, with studies showing anywhere from 1% to 2% of all tumors in cats. However, they can be a persistent and frustrating source of discomfort and recurrent infection once they occur. A broad range of space-occupying lesions can occur in the ear canal, ranging from non-neoplastic benign to malignant entities. The ear is an extensive combination of anatomic structures, allowing for inflammation or neoplasia arising from different tissue types: epithelial, mesenchymal, or nervous tissue.

Review of Clinical Cases

Common external ear canal tumors in cats are nasopharyngeal polyps, squamous cell carcinomas, and ceruminous gland adenocarcinomas, with ceruminous gland tumors being the most common. In some cases, squamous cell carcinoma, fibrosarcoma, or lymphoma can also be identified in the middle ear. One comprehensive study assessed feline aural tumors over 14 years, including 56 malignant and eight benign tumors. Three out of four cats with benign otic tumors had radiography of the skull, which showed concurrent otitis media. Unfortunately, 48% of the 56 cats were diagnosed with malignant tumors had further imaging, showing lysis of the bulla in 19% of the cats and sclerosis of the bulla in 19% of the cats. No changes were noted in 26% of the cats. Researchers found 9% cytologic evidence of lymph node metastasis at the time of diagnosis, and no evidence of paraneoplastic syndromes was noted in any cats.

Survival time data was limited in this retrospective study, with 11 cats not having viable data. Five cats were euthanized at the time of the diagnosis, and the median survival time of the remaining 40 cases was approximately 11 to 12 months. Sixty-five percent of cats died as a result of other causes. Cats with neurologic signs at the time of diagnosis had a marked decrease in survival time, averaging 1.5 months.

The exception to this is the diagnosis of ceruminous gland adenocarcinoma, having a survival time of around 49 months (significantly different than other aggressive tumors such as squamous cell carcinoma or carcinoma in general).

Age, of course, plays a role in these numbers. Inflammatory polyps are still reported as the most common aural tumor in cats, developing anywhere from ages three months to five years of age. These arise from the epithelial lining of the external or middle ear canal and can result in recurrent/persistent otitis externa and, in some cases, extension into otitis media. This should be a consideration for younger cats over more aggressive diagnoses.

In the previous study mentioned, ceruminous gland tumors were more likely to be malignant adenocarcinoma vs. benign adenoma. Still, different studies assessing feline aural tumors have had contrasting findings (one indicated an equal proportion of ceruminous gland adenocarcinoma and squamous cell carcinoma diagnoses, vs. a separate study showing ceruminous gland adenocarcinoma being the more common malignant tumor in the ear canals of cats, mainly males).

Malignant tumors in cats have the inclination to have extensive local involvement/invasion into local tissue, with squamous cell carcinoma being the most aggressive. Overall, cats have a significantly shorter survival time than dogs diagnosed with and similarly affected by malignant tumors; however, this may be because squamous cell carcinoma and other carcinoma types develop more frequently in cats. Unfortunately, squamous cell carcinoma in cats (found in the outer, middle, or inner ear) had a median survival time of 168 days with aggressive surgery vs. 68 days if treated with radiation/chemotherapy or through medical management.

Surgery of some form is the most commonly used treatment for aural tumors in cats, regardless of malignancy, similar to dogs. Aggressive surgical management tended to increase survival time in some cases. Papers assessing survival times in cats and dogs with ceruminous gland adenocarcinoma showed aggressive surgical management substantially increased survival times when compared to the use of conservative surgical excision.

However, given that aggressive surgical management may not always be feasible either through patient stability for anesthesia or through cost, or if a diagnosis of tumor type has not been defined, this author finds that video otoscopy and tumor debulking/histopathology an acceptable first approach to some aural tumors before considering more aggressive surgical intervention if possible. In some cases, tumors are slower growing, less aggressive, and take time to recur, and the patient’s comfort level is temporarily improved. Chronic otitis externa is common in the ear that has the tumor present. So, maintenance ear medications may be necessary to control chronic bacterial or yeast otitis externa secondary to tumor development.

References

1. McGrath AM, Chen CL, Abrams B, et al. Clinical presentation and outcome in cats with aural squamous cell carcinoma: a review of 25 cases (2010–2021). Journal of Feline Medicine and Surgery. 2022;24(10):e420-e432. doi:10.1177/1098612X221119144
2. London C, Dubilzeig R, Vail D, et al. Evaluation of dogs and cats with tumors of the ear canal: 145 cases (1978-1992). JAVMA. 1996; 208 (9): 1413-1418
3. Marino DJ, MacDonald JM, Matthiesen DT, et al. Results of surgery and long-term follow-up in dogs with ceruminous gland adenocarcinoma. J Am Anim Hosp Assoc 1993;29:560-563.
4. Marino DJ, MacDonald JM, Matthiesen DT, et al. Results of surgery in cats with ceruminous gland adenocarcinoma. J Am Anim Hosp Assoc 1993;29: 560-563.
5. Sula M. Tumors and tumorlike lesions of dog and cat ears. Vet Clin Small Anim. 2012 (42): 1161-1178.
6. Legendre AM, Krahwinkel DJ. Feline ear tumors. J Am Anim Hosp Assoc 1981; 17: 1035-1037