Brief Review
    Primary malignant neoplasms of the trachea are uncommon, accounting for less than 1% of all thoracic malignancies. The most common primary tracheal malignancies are squamous cell carcinoma and adenoid cystic carcinoma. Less common tumors include mucoepidermoid and carcinoid tumors. As for tracheal carcinoma, average age of the patients is about 55 yr, and there is male preponderance. Hemoptysis is commonly the first symptom of tracheal carcinoma, but the patient may present with dyspnea, wheezing, or dysphagia. Most of the patients have stridor. Grossly, the tumor may be exophytic, infiltrative, or ulcerated. It may arise from any level in the trachea, and involve only a short segment or extent along the wall for a considerable distance. All histologic varieties are encountered; squamous cell carcinoma is the most common, adenocarcinoma and oat cell carcinoma less frequent.
    Invasion of the mediastinal soft tissues, spread to lymph nodes, and extension into the esophagus are common. Seeding into the lung via the bronchial tree occasionally occurs. Most often the spread is via the hematogenous route to lung, bone, liver, or brain. Radiographically the tumor is usually irregular, lobulated, or annular; most are located above the aortic arch.
    Differential diagnosis should include adenoid cystic carcinoma and mucoepidermoid carcinoma. However, adenoid cystic carcinoma has a tendency to grow submucosally, manifesting the longitudinal extension along the airway.

References
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2. Kwong JS, Adler BD, Padley SP, Muller NL. Diagnosis of diseases of the trachea and main bronchi: chest radiography vs CT. AJR 1993;161:519-22
3. Kwong JS, Muller NL, Miller RR. Diseases of the trachea and main-stem bronchi: correlation of CT with pathologic findings. RadioGraphics 1992;12:645-57
4. Spizarny DL, Shepard JA, McLoud TC, Grillo HC, Dedrick CG. CT of adenoid cystic carcinoma of the trachea. AJR 1986;146:1129-32