Laryngeal and Tracheal Neoplasia
Ronald M. Bright, DVM, MS, DACVS
BASIC INFORMATION
Description and Causes
Laryngeal and tracheal tumors are uncommon in dogs and cats.
Two benign tumors, osteochondroma of the trachea and oncocytoma (rhabdomyoma) of the larynx, are found in younger dogs.
Lymphosarcoma may occur in cats or dogs of any age. Most other
tumors occur in older animals; in general, these tumors are more
likely to be malignant and locally invasive to surrounding tissues.
Examples include the squamous cell carcinoma, adenocarcinoma,
fibrosarcoma, mast cell tumor, osteosarcoma, melanoma, plasmacytoma, and chondrosarcoma.
Clinical Signs
With laryngeal tumors, a voice change, swallowing problems,
coughing, and difficulty breathing are common. Tracheal masses
most often result in difficulty breathing, especially on inspiration
(breathing air in). Coughing, noisy breathing, cyanosis (blue gums
caused by lack of oxygen), and exercise intolerance can also be
associated with obstructive tumors of the trachea.
Diagnostic Tests
Certain changes on the physical examination are suspicious for
a laryngeal or tracheal inflammation or tumor, including the
following:
• Abnormal respiratory sounds may be auscultated (heard) with
a stethoscope.
• Musical or wheezing noises may be heard over the trachea.
• Pressing on the trachea easily elicits a cough from increased
sensitivity of the tracheal lining.
• Many tracheal tumors can be palpated (felt), whereas most
laryngeal tumors cannot.
• Lymph nodes in the neck may be enlarged with a malignant
laryngeal tumor and occasionally with a tracheal tumor.
Further testing is usually needed to confirm the presence of a mass.
Routine laboratory tests and chest x-rays may be done to look for
evidence of inflammation or tumors elsewhere and to rule out
other diseases that cause similar signs. Bronchoscopy (examination of the airway with a fiberoptic viewing scope) often confirms
the presence of a mass, helps define the extent of the tumor, and
allows tissue to be obtained for a biopsy. A biopsy and microscopic analysis are needed to determine the tumor type.
TREATMENT AND FOLLOW-UP
Treatment Options
Some laryngeal tumors (oncocytoma) can be surgically removed,
although laryngeal function may be impaired. More malignant
laryngeal tumors require aggressive surgery (partial or complete
removal of the larynx) followed by a permanent tracheostomy.
Removal of a portion of the tumor in an attempt to preserve laryngeal function is an option when follow-up chemotherapy is possible (such as with lymphoma or mast cell tumors).
If a tumor is attached to the trachea by a narrow stalk, it may
be possible to remove it at the time of bronchoscopy. For larger,
broader-based tumors, the mass and a portion of the trachea must
often be removed surgically. The greatest amount of trachea that can
be removed is eight cartilage rings in length. Most infiltrative tumors
require follow-up chemotherapy or radiotherapy because complete
removal is not possible at the time of surgery. Chemotherapy, often
combined with surgery, is the preferred treatment for some tumors,
including lymphoma, mast cell tumors, and plasmacytomas.
Follow-up Care
These patients require intensive postoperative monitoring, because
breathing problems are common. Corticosteroids may be recommended to decrease swelling and inflammation while chemotherapy or radiation therapy is proceeding. A temporary or permanent
tracheostomy may be required if respiratory problems are severe.
Follow-up examinations, repeated laboratory tests, and chest x-rays
are often recommended on a regular basis during therapy.
Prognosis
Prognosis for laryngeal oncocytoma is good. Osteochondromas
are also associated with a good prognosis if the tumor can be completely removed. Most other laryngeal tumors carry a guarded
(uncertain) to poor prognosis. Malignant tumors of the trachea
respond variably to therapy and carry a poor prognosis.
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