Ear canal 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 skin. Tumors of the external ear canal and outer ear are more common than tumors of the middle or inner ear. Ear canal tumors are more common in cats than in dogs but, overall, these tumors are relatively uncommon compared with skin tumors elsewhere on the body.
Although the exact cause of ear canal tumors is unknown, it is thought that longterm inflammation of the ear canal may lead to abnormal growth and development of tissue, and finally to the formation of a tumor. Thickening secretions from earwax glands during episodes of inflammation of the external ear canal may stimulate the production of cancerous cells. Ear canal tumors are more likely to be malignant than benign in cats.
Middle-aged to older cats are more likely to develop benign and malignant ear canal tumors, while young cats (3 months to 5 years old) are more likely to develop inflammatory polyps (see Ear Disorders of Cats: Inflammatory Polyps). Signs of ear canal tumors include a continuing waxy, pus-filled, or bloody ear discharge in one ear, foul odor, head shaking, ear scratching, swelling, draining abscesses in the region below the affected ear, or deafness. If the middle or inner ear is involved, the cat may have loss of balance or coordination, 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 is possible.
Referral to a board-certified surgical specialist is often recommended when dealing with ear canal tumors, especially when the middle ear is involved (see Skin Disorders of Cats: Tumors of the Skin in Cats).
Nasopharyngeal polyps are small, pinkish inflammatory growths of connective tissue that are found in the external ear canals of young cats (usually between the ages of 3 months and 5 years). They also occur in the mucous membranes lining the throat mucosa and auditory tube (the channel connecting the nasopharynx to the middle ear). These polyps may be present at birth or caused by viral or bacterial infection. Bacterial infection of the external or middle ear canal due to obstruction of the ear canal or round bone behind the ear may also be present. Signs of inflammatory polyps will be similar to those seen in other middle ear problems, including problems with balance, coordination, or an inflammation of the outer (visible) portion of the ear.
Diagnosis involves examination of the vertical and horizontal ear canals using an otoscope (an instrument that allows a veterinarian to see deep into the ear canal) while the cat is sedated. Pus-filled discharge may need to be gently suctioned from the ear canal to see the polyp. Additional tests such as computed tomography or magnetic resonance imaging may be used if a mass is suspected in the round bone behind the ear.
Surgery is often used to remove the polyp. Your veterinarian will take care to completely remove the entire polyp and stalk; incomplete removal usually leads to rapid regrowth of the polyp.
Earwax Gland Tumors
Benign or malignant tumors that develop from the modified earwax glands in the external ear canal occur occasionally in middle-aged or older cats. These tumors are more likely to be malignant than benign. Cats with a history of longterm inflammation of the ear are more likely to develop earwax gland tumors.
Malignant earwax tumors are firm, dome-shaped, and pink-white. They often have stalk-shaped lumps or flattened patches with slow-healing sores. Because many tumors completely obstruct the ear canal, they are often associated with inflammation of the external or middle ear and pus-filled or bloody discharge. Loss of balance is common if there is middle ear involvement. Malignant earwax tumors can spread to nearby lymph nodes and salivary glands, so your veterinarian may recommend that they be removed.
Surgical removal of benign ear canal tumors may be accomplished by removing part of the ear canal. This is helpful in most cases unless there is involvement of the round bone behind the ear. Laser surgery has also been used. Completely opening the ear canal and surgically dividing the bone in the middle ear is the only recommended surgery for removal of malignant ear canal tumors.
The best treatment program for your cat will depend on many factors, including your pet's age and the size and location of the tumor. Your veterinarian will recommend a treatment program that has the best chances for a positive result.
Last full review/revision July 2011 by T. Mark Neer, DVM, DACVIM; Michele R. Rosenbaum, VMD, DACVD; Patricia D. White, DVM, MS, DACVD