Tracheal neoplasms occur infrequently, accounting for fewer than 1% of all malignancies. [1, 2] According to the National Cancer Institute (NCI) Surveillance, Epidemiology and End Results (SEER) 1973-2004 database, primary carcinomas of the trachea occur at a rate of 2.6 new cases per million people per year. During this period, 578 cases were reported: 322 men (55.7%) and 256 women (44.3%). 
Patients with tracheal tumors can present with catastrophic airway obstruction. In addition to primary neoplasms of the trachea, secondary tracheal involvement can occur from tumors of surrounding tissues such as thyroid, esophagus, larynx, and lung.
Of all primary tumors of the trachea, 80% are malignant; squamous cell carcinoma (SCC) was the predominant histology type at 259 (44.3%) tumors, followed by adenoid cystic carcinoma (ACC) at 16.3%. The remaining tumors are widely varied and include both malignant and benign histotypes. 
Tracheal tumors are eminently treatable when diagnosed in the early stages. However, their usually insidious onset often leads to a delay in diagnosis, making these potentially treatable lesions difficult to manage and often fatal. Thus, early diagnosis is the most important factor affecting overall survival.
Surgical resection is the mode of treatment with the best hope for cure. Radiotherapy can be offered if the patient cannot tolerate surgical treatment. Chemotherapy can also be given after initial treatment with surgery, radiotherapy, or both. Laser removal of the intratracheal tumor is usually performed for palliation.
The average length of the adult trachea is 11 cm from the inferior border of the cricoid cartilage to the carinal spur. The trachea courses from an immediately subcutaneous position in the neck to a position against the esophagus and prevertebral fascia at the carinal level.
There are 18-22 cartilaginous rings in the human trachea, with approximately twp rings per centimeter. The airway in an adult is roughly elliptical. The only complete cartilaginous ring in the normal airway is the cricoid cartilage of the larynx.
Calcification of the cricoid is not unusual, and calcification of other cartilaginous rings occurs with age. The attachments of the trachea allow relatively free vertical movement in relation to other anatomic structures. The most fixed point below the cricoid lies where the aortic arch forms a sling over the left main bronchus.
The tracheal mucosa is columnar and ciliated. It is closely apposed to the tracheal cartilages and to the interannular tissues between them. Mucous glands are liberally present. In patients with chronic bronchitis, particularly those who smoke heavily, squamous metaplasia may occur.
Typically, tracheal tumors grow slowly. Benign neoplasms tend to be smooth, rounded masses less than 2 cm in length. The presence of calcium seen on plain radiography films, though common, does not reliably differentiate benign and malignant tumors. Malignant tumors, specifically SCCs, may be exophytic or ulcerative.
Benign tumors can arise from any of the tissues present in the trachea. Malignant tumors probably follow a carcinogenesis similar to that of lung cancers. Most of these tumors occur sporadically. Apart from squamous papillomas, which have been associated with viral infection, no consistent etiology has been found. Smoking is a known risk factor.
Primary tracheal tumors are very rare, occurring in approximately 0.1 person per 100,000 population. Most (80-90%) are malignant. The incidence of primary tracheal carcinoma is much lower than that of laryngeal or endobronchial cancer. Lung cancers are 180 times more common than tracheal malignancies. Smoking is a commonly associated risk factor.  In some studies, 40% of patients had prior, concurrent, or later carcinoma of oropharynx, larynx, or lung. Tracheal tumors are three times more common in males than in females. Peak incidence occurs in the fifth and sixth decades of life.
Median survival for all patients after diagnosis of malignant tracheal tumors is 6 months, but survival time varies widely, depending on the histologic type of the tumor. General overall 5-year survival for all patients with tracheal carcinoma was 27.1% (95% confidence interval, 23.1-33.3%), with an improved outcome for patients with localized disease versus regional or distant disease. A tumor histology of SCC yielded a 5-year survival rate of 12.6% versus 74.3% for ACC.  Following resection, carcinoid tumors carry excellent 5-year and 10-year survival rates in most series (95% and 90%, respectively).
According to Xie et al, radiation therapy may improve outcomes in patients with primary squamous cell tracheal malignancies.  Furthermore, there was a statistically significant survival benefit for patients who underwent any type of surgical therapy compared with those who did not.