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. Rapidly growing or spreading (malignant) 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. Bacterial infections that lead to excess secretions from earwax glands may also stimulate the production of cancerous cells. Ear canal tumors are more likely to be malignant than benign in cats, especially those more than 11 years old.
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 below). 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.
The most common external ear canal masses reported in cats are nasopharyngeal polyps, squamous cell carcinomas, and earwax gland tumors. Lymphoma, fibrosarcoma, and squamous cell carcinomas are occasionally seen in the middle or inner ear of cats. The most common of these are discussed below.
Referral to a board-certified veterinary surgeon is often recommended when dealing with ear canal tumors, especially when the middle ear is involved. Also see Tumors of the Skin.
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 upper throat to the middle ear). These polyps may be present at birth or caused by longterm bacterial middle ear infections. Bacterial infections of the middle ear canal are often associated with longterm infections of the upper respiratory tract (nose, throat, and sinuses). 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 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. Treatment for an associated ear infection may also be necessary.
Benign or malignant tumors that develop from the modified earwax glands (called ceruminous glands) in the external ear canal occur occasionally in middle-aged or older cats. These tumors are more likely to be malignant than benign, especially in cats more than 11 years old. 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. Less invasive surgery can be done with a laser and a video otoscope (a special type of camera that allows veterinarians to see the ear canal). This is helpful in most cases unless there is involvement of the round bone behind the ear. 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.
Also see professional content regarding tumors of the ear canal.