What are tumors of the ear canal?
Tumors of the ear canal are abnormal growths that can develop from any part of the ear canal (the skin, the glands of the skin that produce earwax and oil, and the underlying connective tissues, muscles, and bones). Ear canal tumors can be benign or malignant. Benign tumors do not spread, while malignant or cancerous tumors can spread to the surrounding tissues or even other areas of the body (metastasis). Tumors of the external ear canal are more common than tumors of the middle or inner ear.
In dogs, the most common external ear canal tumors are ceruminous gland adenomas (benign) and adenocarcinomas (malignant). Other tumors include inflammatory polyps, papillomas, sebaceous gland adenomas, and more.
In cats, the most common external ear canal tumors are nasopharyngeal polyps, squamous cell carcinomas, and ceruminous gland adenocarcinomas.
Lymphoma, fibrosarcoma, and squamous cell carninomas are occasionally seen in the middle or inner ear of dogs and cats.
What causes these kinds of tumors?
The reason why a particular pet may develop this, or any other tumor or cancer, is not straightforward. Very few tumors and cancers have a single known cause. Most seem to be caused by a complex mix of risk factors, some environmental and some genetic or hereditary. Although there does not appear to be a genetic or hereditary cause for ear canal tumors, chronic inflammation is believed to play a role. German Shepherds and Cocker Spaniels, for example, are at increased risk of developing these tumors. This may be related to the tendency of both breeds to have recurrent and severe ear infections.
What are the clinical signs of ear canal tumors?
Initially, these types of tumors may appear as one or more pink, white, or purple nodular masses in the ear canal. If benign, they may grow to a certain size and may or may not be problematic. If malignant, they may grow, ulcerate (break open) and bleed, and nearly invariably become infected, causing recurrent or chronic ear infections. As they grow, they can narrow and even fill (and obstruct) the ear canal.
The most common clinical signs of pets with ear canal tumors include an inflamed, itchy and painful ear, persistent odorous discharge (that can be waxy, pus-filled, or bloody), head shaking, and ear scratching. Sometimes pets will shake or scratch hard enough to cause an ear hematoma (a blood blister). Occasionally draining abscesses may form just below the ear. If the middle or inner ear is involved, pets may experience head tilt, circling, loss of balance and coordination, nystagmus (darting of the eyes back-and-forth), Horner’s syndrome (see photo), facial paralysis (with facial drooping, salivation, and difficulty eating), loss of hearing, and other neurologic signs.
(Image via Wikimedia Commons / Joel Mills (CC BY-SA 3.0.)
How are these kinds of tumor diagnosed?
If deep in the ear canal, these tumors may be difficult to see and therefore diagnose. If the ear canal is severely inflamed, the inflammation may need to be alleviated first to more clearly see the mass. Once the mass is identified, it may (or may not) be possible to take a sample of the tissue, depending on the location. If the mass can be accessed, fine needle aspiration (FNA) or biopsy will be performed. FNA involves taking a small needle with a syringe and suctioning a sample of cells directly from the tumor and placing them on a microscope slide. A veterinary pathologist then examines the slide under a microscope. A biopsy is surgical removal of a piece of the tumor. The tumor tissue is then examined under the microscope. This is called histopathology.
If a diagnosis of malignancy is made from the FNA or biopsy, a CT scan of the head and neck region may be performed to determine how invasive the tumor is and plan a surgical approach. Staging (searching for potential spread to other locations in the body) is highly recommended for malignant tumors, as they tend to spread. This may include bloodwork, urinalysis, X-rays of the lungs, and possibly an abdominal ultrasound. If any lymph nodes appear to be enlarged or firmer than normal, samples may be taken to look for spread.
How do these types of tumor typically progress?
Benign tumors, such as inflammatory polyps, typically only grow to a certain size, but are often irritating and interfere with the ear’s normal function, resulting in waxy buildup and chronic infections. The biggest concern with malignant tumors (other than the possibility of metastasis) is local spread. If the tumor is not treated, it may continue to grow and invade the surrounding tissues, causing pain and increasing the risk of the more serious clinical signs and complications listed above.
What are the treatments for these types of tumor?
The treatment of choice for ear canal tumors is surgical excision. This is curative for benign tumors that are completely removed. Laser surgery may be an option. More extensive surgery is required for malignant ear canal tumors. One procedure, called total ear canal ablation and bulla osteotomy (TECA-BO), involves removing the outer and inner ear canal, as well as the tympanic bulla (the middle ear), leaving only the ear flap remaining.
If complete removal of the tumor is not possible, radiation therapy may be recommended to treat the remaining tumor cells. Radiation therapy may also be recommended for large tumors that cannot be surgically removed, to slow tumor growth or relieve pain. Chemotherapy may be an option if the tumor is highly malignant or if there is evidence of metastasis.
Is there anything else I should know?
It is important to recognize that tumors of the ear canal may grow without much outward evidence, only causing subtle signs in your pet. If your pet suffers from recurrent or chronic ear infections, or shows signs of pain or discomfort, rechecking with your veterinarian at frequent intervals may assist with early detection.