Thoracic Imaging 2003 - Society of Thoracic Radiology

Tracheobronchial Tumors
Jo-Anne O. Shepard, M.D.
Director, Thoracic Radiology
Massachusetts General Hospital
BENIGN TUMORS AND CYSTS
Benign tumors of the trachea are very rare and account for
10% of tracheal tumors. Ninety percent of benign lesions are
encountered in the pediatric age group. Benign tumors represent
a large group of diverse lesionsthat manifest as sharply defined
masses with no invasive characteristics. They are usually homogeneous,
and the majority of lesions have no characteristic features
to differentiate them by radiologic means.
Papillomas
Papillomatosis is the result of a multicentric viral infection
with the human papilloma virus. Papillomas occur either singly
or as multiple, irregular tumor excrescences that generally arise
from the true vocal cords. Papillomas most often involve the
superior surfaces or free margins of the vocal cords and less commonly
occur in the supraglottis and subglottis. Papillomas are
divided into juvenile and adult groups. Papillomas of the juvenile
group often manifest as multiple lesions most commonly found in
the larynx. The papillomas may recur or may spread diffusely
through the trachea, bronchi and lungs following excision. In the
lungs, sheets of squamous cells proliferate within alveoli forming
nodules that characteristically cavitate. The adult type of lesion
often presents as a solitary mass with a lesser propensity to recur
after removal. Transformation of the lesions into invasive squamous
cell carcinoma is well known.
Radiographically, the tracheal walls may appear thickened
and nodular in appearance, either in a focal or diffuse fashion,
sometimes visible on chest radiographs, but best demonstrated on
CT. Multiple pulmonary nodules with and without cavitation can
be identified on chest radiographs and CT.
Chondromas
Chondromas of the larynx are uncommon lesions that occur
most frequently in middle age men. The tumor is smooth, submucosal,
and firm in consistency. On the radiographic and CT
examination the tumor presents as a sharply defined mass and frequently
contains mottled calcifications. Radiologically, a chondroma
cannot be distinguished from a chondrosarcoma; this distinction
also may be difficult on histopathologic examination.
The most common location is the inner surface of the cricoid lamina
(70%). Less often, chondromas arise from the thyroid, arytenoid,
or epiglottic cartilages. On rare occasions, chondromas
may be situated on the upper surfaces, free margins, or undersurfaces
of the vocal cords. Chondromas may occur in the trachea
but occur less commonly than laryngeal chondroma.
Hemangiomas
Hemangiomas are uncommon lesions in the larynx and even
less commonly in the trachea. The pediatric type of hemangioma
usually manifests by 6 months of age, is subglottic in location,
and causes signs of airway obstruction. Typically, these children
exhibit hoarseness, stridor, and dysphagia with poor feeding. In
the anteroposterior radiographic film there is subglottic often
asymmetrical narrowing and evidence of a distinctive homogeneous,
sharply defined soft tissue mass. In adults, laryngeal
hemangiomas usually arise in the supraglottic larynx as a sharply
defined, homogeneous mass that may contain phleboliths. Most
of the reported cases are of the cavernous variety, as opposed to
capillary hemangiomas, which are seen in infancy.
Other benign tumors
Miscellaneous benign tumors are encountered in the larynx
and trachea. These include neurogenic tumors, pleomorphic adenoma,
oncocytic tumor, granular cell tumor, paraganglioma, lipoma,
fibrous histiocytoma and rhabdomyoma and hamartomas.
Conventional radiographs do not usually reveal any characteristic
features that allow a specific histopathologic diagnosis. CT can
identify fatty attenuation within hamartomas and lipomas and
increased contrast enhancement within paragangliomas. A chondroid
matrix can be identified within chondromas and chondrosarcomas.
Laryngoceles
Various cystic lesions are encountered in the larynx which are
either retention cysts or laryngoceles. Laryngoceles are air- or
fluid-filled outpouchings of the mucosa of the laryngeal ventricles.
They extend from the ventricle into the adjacent aryepiglottic
fold and are then referred to as internal laryngoceles. They
may, however, herniate through the thyrohyoid membrane and
result in external laryngoceles. They are characterized by an
air-filled structure that is usually well defined. Intralaryngeal
expansion leads to a variable degree of airway obstruction,
depending on the size of the lesion. If these laryngoceles are filled
with fluid, they manifest as homogeneous, dense masses and cannot
be differentiated from a benign tumor.
Tracheal cyst or tracheocele
A tracheal cyst is a thin walled air containing paratracheal
cavity that is visible on chest radiographs and chest CT examinations.
The tracheal cyst is a circumscribed saccular tracheal out
pouching of the posterior wall of the trachea. The cyst may rarely
contain an air-fluid level. Dynamic bulging can be observed during
a Valsalva maneuver at fluoroscopy or on CT. This condition
occurs through a localized weakness of the membranous part of
the tracheal and is theorized to be associated with obstructive
lung disease.
MALIGNANT LESIONS
Epithelial tumors
Larynx
The majority of laryngeal malignancies (90%) represent
epithelial neoplasms. Among these, about 50 to 70% of laryngeal
cancers are glottic in nature, about 30 to 35% represent supraglottic
carcinomas, and 4 to 6% represent subglottic carcinomas.
Tumor size, location, and histologic grading are important parameters
that determine the occurrence of lymph node metastases.
Metastatic lymph nodes are more common when the primary
tumor in the supraglottic larynx is greater than 2.0 cm in diameter
and is poorly differentiated. Supraglottic carcinomas arise
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THURSDAY