Ear Tumors in Dogs and Cats
Abnormal growths or tumors can develop in any part of the ear canal - in the external, middle, or inner ear canal. These tumors can be benign or malignant. Tumors that don’t spread are known as benign tumors, while those that spread to the surrounding tissues or other parts of the body are malignant or cancerous tumors. There is a higher rate of tumor development in the external ear canal than in the middle or inner ear of dogs and cats. Keep reading to learn more about ear tumors in pets, including symptoms, diagnosis, and treatment.
According to the College of Veterinary Medicine, University of Illinois at Urbana-Champaign, “masses or tumors should always be a concern in dogs or cats with recurrent ear infections, especially when the infections are unilateral or the animal is middle-aged or older”.
Several types of ear tumors can develop in the ear passages of dogs and cats. Benign ear tumors are more common among middle-aged dogs and cats, while malignant tumors are more common in senior dogs and cats that are more than 11 years of age. Nasopharyngeal polyps are more common in young cats ages 3 months to 5 years old. Malignant tumors in the external ear canal and ear flap are more common in cats than in dogs.
What causes the development of ear tumors?
The exact cause of ear tumor development in dogs and cats has not been fully established, but experts have forwarded several theories to explain the growth. These include chronic or long-term inflammation of the ear canal or frequent episodes of otitis externa (inflammation of the outer ear). Pets with a history of long-term (chronic) otitis externa have an increased risk for ear tumors. The incidence of ear tumors, both benign and malignant, is more prevalent in American Cocker Spaniels than in other canine breeds. This predisposition is likely brought about by chronic inflammation that is common to the breed.
What happens when a dog or cat has an ear tumor?
When a tumor is present in the ear passage, there is a decrease in the diameter of the canal. This can eventually impede the drainage of pus when there is an infection in the middle or inner ear. Chronic infection and inflammation may lead to neoplastic (cancerous) changes in the tissues of the ear.
Tumors in the ear canal can appear like firm nodules which can be pinkish, white, or purple in color. When an ear canal tumor becomes ulcerated, it can lead to bleeding or ear discharge. The affected cat or dog may also feel pain or intense itching. There may be a distinctly strong odor from the ear. When the ear canal tumor invades nearby tissues or causes infection, there may be a display of neurological symptoms such as head tilting, circling, unable to blink, or loss of balance.
Types of Ear Tumors in Dogs and Cats
- Ceruminous Gland Adenoma (Benign Ear Wax Gland Tumors)
- Ceruminous Gland Adenocarcinoma (Malignant Ear Wax Gland Tumors)
- Nasopharyngeal Polyps (Inflammatory Polyps)
- Squamous Cell Carcinoma
Ceruminous Gland Tumors
The ceruminous glands are sweat glands that are located in the external portion of the ear canal. The secretion of the glands combines with the secretion of the sebaceous glands to form ear wax (cerumen). The development of ceruminous gland tumors (ear wax gland tumors) is usually secondary to otitis externa (the most common type of ear infection).
Among other types of tumors in the ear canal, ceruminous gland adenoma and adenocarcinoma are most commonly encountered in dogs and cats. Ceruminous gland adenocarcinoma is locally aggressive and may spread to nearby lymph nodes as well as the parotid salivary gland. On the other hand, ceruminous gland adenomas are benign tumors. Although they don’t spread or invade other areas of the body, they can grow and exert pressure on adjacent tissues.
These tumors are often in the vertical ear canal in dog breeds other than the American Cocker Spaniel. In the American Cocker Spaniel, these tumors can be found in the horizontal ear canal as well.
Squamous Cell Carcinoma
These are malignant tumors that are known for being very locally invasive. The squamous cell carcinoma is the most common tumor originating from the middle ear in pets. Fortunately, cases of squamous cell carcinoma in the middle and inner ear of dogs and cats are quite rare.
Auricular (earlobe) squamous cell carcinoma in cats is often linked to excessive exposure to the sun or ultraviolet rays. Cases are more common in white-colored cats and those with white ears. If diagnosed early, treatment is usually successful. There is, however, a decreased risk among Siamese, Persian, and Himalayan cats which can be attributed to their protective pigment.
Nasopharyngeal Polyps (Ear Polyps)
Ear polyps are inflammatory growths found in the external ear canal of young cats. They are benign, inflammatory growths that develop in the middle ear, back of the throat, or Eustachian tube and may extend into the pharynx. Ear polyps have a distinct pinkish-white color. The cause of ear polyps has not been fully established but it is thought that it’s a reaction to infectious agents inhaled by cats. While polyps are most common in cats, they do develop in dogs. In dogs, the growth typically extends into the ear canal instead of into the nasopharynx (back of the throat).
Diagnosis of Ear Tumors in Dogs and Cats
A veterinarian usually performs a deep otoscopic exam to identify the tumor. Sedation or anesthesia may be necessary to allow a thorough exam and get a tissue sample of the tumor for biopsy. A CT scan or MRI may also be recommended to determine the extent of the tumor. If it’s a malignant tumor, a lymph node aspirate or biopsy, as well as chest x-rays, may be necessary to check if cancer has spread or metastasized.
Treatment of Ear Tumors in Dogs and Cats
Surgical excision of ear canal tumors is the treatment of choice. This is particularly helpful in the complete removal of benign tumors. Surgical removal of benign ear canal tumors may be accomplished via lateral ear canal resection for access to the mass. Laser surgery, especially when used in conjunction with a video otoscope, has made intraotic removal of these tumors relatively easy without having to open the canal surgically. Unfortunately, the recurrence rate for malignant ear tumors is >75%.
For malignant tumors, aggressive surgery is the gold standard for treatment, particularly if the tumor has already caused irreparable damage to the ear canal. The procedure, which is often referred to as Total Ear Canal Ablation (TECA), includes ablation (surgical excision) of the ear canal and cleaning out the inner part of the ear (bulla osteotomy).
In some cases, radiation therapy may be performed to slow down the tumor growth and alleviate pain. Radiation may also be indicated when surgical excision of the tumor fails to completely remove the growth. If biopsy results show the tumor to be very aggressive or there is already evidence showing metastasis, chemotherapy may be recommended.
Malignant ear tumors tend to be less aggressive in dogs compared to cats. After aggressive surgery, most dogs can live longer than 3 years, while the average for cats is only about 1 year. In a study that evaluated malignant tumors of the ear canal of dogs and cats, results showed that the median survival time of dogs with malignant aural tumors was > 58 months, whereas that of cats was 11.7 months.
Prognosis for Dogs and Cats with Ear Tumors
The prognosis of ear tumors in dogs and cats will depend on several factors and includes the animal’s age, health, location of the tumor, and the type of tumor.
Prognosis is significantly decreased when only conservative surgery is performed. The prognosis is worse when the tumor has spread to the inner parts of the ear. Prognosis is poor when cancer has spread to the lymph nodes, lungs, or blood vessels. The more aggressive squamous cell carcinoma also has a poor prognosis. Extensive tumor involvement and the manifestation of neurologic signs at the time of diagnosis also have a poor prognosis.
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