Tumors may develop from any of the structures lining or supporting the ear canal, including the outer layer of skin, the glands that produce earwax and oil, or any of the bones, connective tissues, muscles, or middle layers of the skin. Tumors of the external ear canal and pinna are more common than tumors of the middle or inner ear. Cocker Spaniels are more likely to have ear canal tumors than other breeds of dogs. Middle-aged dogs are more likely to have benign ear tumors, while those in dogs more than 11 years old are more likely to be malignant.
Although the exact cause of ear canal tumors is unknown, it is thought that longterm inflammation of the ear canal may lead to an abnormal growth and development of tissue, and finally to the formation of a tumor. Thickening secretions from earwax glands during inflammation of the external ear canal may stimulate the production of cancerous cells. Ear canal tumors are more likely to be benign than malignant. Of those that are malignant, less than 10% spread beyond the local area.
Signs of ear canal tumors include ear discharge (waxy, pus-filled, or bloody) in one ear, a foul odor, head shaking, ear scratching, and swelling or draining abscesses near the ear. If the middle or inner ear is involved, the dog may have loss of balance and coordination, deafness, head tilt, and other neurologic signs. In any case of inflammation in one ear that does not respond to treatment, a tumor of the ear canal should be suspected by your veterinarian.
Benign or malignant tumors of the earwax glands (called ceruminous glands) can develop in the external ear canal.. These tumors can appear as smooth or bumpy stalk-shaped lumps or flattened patches that rise off the lining of the ear canal. A deep biopsy of the tissue is necessary for diagnosis. Computed tomography (CT scan) or magnetic resonance imaging (MRI) may also be needed to determine whether the tumor is invading surrounding tissues, including the middle ear.
Surgical removal of benign ear canal tumors is possible in many cases. Laser surgery has also been used. More extensive surgery is required for malignant ear canal tumors. Average survival time of animals with malignant ear canal tumors has been reported to be almost 5 years in dogs; however, dogs with extensive tumor involvement had a less favorable outlook. Radiation therapy can be used to treat incompletely removed malignant earwax gland tumors, with a 56% 1-year survival rate reported.
Your veterinarian can discuss your pet’s individual health status and provide you with a more complete outlook for the possible result of any surgery or other treatment.
Also see professional content regarding tumors of the ear canal.