Tracheal Tumors

Tracheal neoplasms occur infrequently, accounting for less than 1% of all malignancies. In the nearly 3 decades between 1962 and 1989, 198 patients with primary neoplasms of the trachea were treated at Massachusetts General Hospital.

Of all primary tumors of the trachea, 80% are malignant, with adenoid cystic carcinoma and squamous cell carcinoma being the most common. In spite of their low incidence, these tumors represent potentially lethal phenomena that are eminently treatable when diagnosed before the onset of complications.

History of the Procedure: Although tracheostomy is one of the oldest procedures in surgery, the first postmortem description of a tracheal fibroma was by Lieutaud in 1767. Later, in 1861, Turck used indirect laryngoscopy to diagnose a tracheal tumor in a living patient. Direct endoscopic visualization of a tracheal neoplasm was reported by Killian in 1897.

Problem: Tracheal tumors are potentially lethal but are eminently treatable when diagnosed before the onset of complications.

Frequency: 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 laryngeal or endobronchial cancer. Lung cancers are 180 times more common than tracheal malignancies. All of the reported patients smoked, and 40% had prior, concurrent, or later carcinoma of oropharynx, larynx, or lung. These tumors are 3 times more common in males than in females. Peak incidence occurs in the fifth and sixth decades of life.

Etiology: Benign tumors can arise from any of the tissues present in the trachea. Malignant tumors probably follow a similar carcinogenesis to 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.

Pathophysiology: The tracheal mucosa is columnar and ciliated. It is closely applied to the tracheal cartilages and to the interannular tissues between them. Mucous glands are liberally present. In patients with chronic bronchitis, particularly in those who smoke heavily, squamous metaplasia may be found.

Typically, tracheal tumors grow slowly. Benign neoplasms tend to be smooth, rounded masses shorter than 2 cm in length. The presence of calcium upon plain radiography does not reliably differentiate between benign and malignant tumors.

Clinical: The presentation of primary tumors of the trachea is variable. In a series of 329 patients with primary tracheal malignancies, dyspnea was found to be the most frequent symptom (71%), followed by cough (40%), hemoptysis (34%), asthma (19.5%), and stridor (17.5%). Symptoms related to involvement of adjacent structures, such as hoarseness and dysphagia, were less frequent.

The first symptom may be shortness of breath after activity, which gradually worsens. Acute respiratory difficulty may not be present until the airway is almost completely occluded. A persistent cough, wheezing, or stridor might be seen, as might recurring attacks of respiratory obstruction owing to secretions.

Delay in diagnosis occurs because the pulmonary fields remain normal on a chest radiograph. If the patient has hemoptysis, a diagnosis is more likely to be made because bronchoscopy will be performed even in the presence of a normal chest film.

Another presentation is with repeated episodes of either unilateral or bilateral pneumonia that respond to antibiotics and physiotherapy. In the absence of hemoptysis, a diagnosis of adult-onset asthma often is made, thus delaying definitive treatment. In one series, delayed diagnosis of more than 6 months after symptoms onset occurred in one third of patients.

Differential diagnosis

Bronchial asthma
Emphysema
Upper airway obstruction

Relevant Anatomy: The average length of the adult trachea is 11 cm from the inferior border of the cricoid cartilage to the carinal spur. It 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 2 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.

Contraindications: Very little reason exists to delay surgery on a primary tracheal neoplasm because these patients tend to progress rapidly once symptomatic due to the near-total tracheal luminal obstruction that frequently is present.

Bronchoscopic biopsy is contraindicated in the presence of highly vascular tumors (eg, hemangiomas).

Histologic Findings:

Malignant tumors

Adenoid cystic carcinoma: This tumor is seen primarily in individuals aged 13-79 years and is evenly distributed between males and females. It grows so slowly in many patients that it appears to be benign in behavior, even after metastases have occurred to the lungs. Some lesions are highly malignant and spread to pleura and lungs before they are discovered. Remote metastasis occurs most often to lung and bone.

Bronchial carcinoids: These are derived from the neuroendocrine cell line, as are other amine precursor uptake and decarboxylation cell tumors. They are part of a spectrum of tumors derived from the same cell line, which ranges from typical carcinoids (which usually follow a benign course) to the more aggressive atypical carcinoids and the highly malignant small cell lung cancer. The cells are capable of secreting active peptide hormones, as do other carcinoids. Rarely is this of clinical significance because the carcinoid syndrome is quite rare with bronchial or tracheal tumors. Thus, most tumors present with obstructive-type symptoms.

Neuroendocrine tumors: In a newer classification, carcinoid tumors are part of a larger group of lesions referred to as neuroendocrine tumors of the lung. These include histologically low-grade tumors; typical and atypical carcinoids; and histologically high-grade lesions, large cell neuroendocrine carcinoma, and small cell carcinoma. In addition, squamous cell carcinomas, adenocarcinomas, and large cell carcinomas may exhibit neuroendocrine features. It is likely that this classification is applicable to lesions occurring in the trachea and the lung.

Squamous cell carcinoma: This may present as a well-localized lesion of exophytic type or as an ulcerating lesion. Multiple lesions with interspersed normal trachea and superficial infiltrating carcinoma, which may extend over the whole length of the trachea, also occur. Approximately one third of the patients have mediastinal or pulmonary metastases at the time of initial diagnosis. Squamous cell carcinoma of the trachea is distributed comparably to squamous bronchogenic carcinoma with respect to age (50-70 y) and sex (male-to-female ratio of 3:1).

Benign tumors

Squamous papillomas: These are the most common of the benign tumors and are associated with human papilloma virus types 6 and 11. They frequently occur in the larynx and present as vocal changes. They appear as irregular, papillary, or villous processes covered by thick squamous epithelium blending into the normal respiratory epithelium. They may represent a premalignant type of lesion. Simple extirpation results in almost universal recurrence, and radical resection is advocated for complete removal. Modern technological modalities for control are being applied to avoid radical resection.

Cartilaginous tumors: Next in frequency, they appear as gray-to-white firm masses with focal gritty areas secondary to calcification and are composed of cartilage and bone cells with an intact overlying mucosa. Generally occurring in the fifth and sixth decades of life and with a potential for sarcomatous change, complete resection is needed.

Other tumors

Other tracheal tumors are exceedingly rare and include hamartomas, hemangiomas, neurilemomas, leiomyomas, and histiocytomas. Thyroid tissue may be present ectopically within the trachea. This too has a potential for malignant change and should be excised.
 

Medical therapy: In general, medical therapy has not been useful in the treatment of tracheal tumors. Successful treatment of squamous papillomatosis with interferon has been reported. Steroids once were used in tracheal hemangiomas, the majority of which now are treated by observation only because spontaneous regression is common.

Surgical therapy: Surgical resection is the mode of treatment with the best hope for cure. Radiotherapy can be offered if the patient cannot receive surgical treatment. Chemotherapy also can be given after initial treatment with surgery, radiotherapy, or both. Laser removal of the intratracheal tumor usually is performed for palliation.

In the series of 198 patients reported by Grillo and Mathisen, 70 (35%) had squamous cell carcinoma. Of these, 44 (63%) were resected, with an operative mortality rate of 5%. The overall survival rate was 27% at 3 years and 13% at 5 years.

Laser resection as definitive treatment is appropriate for (1) patients with metastatic disease, (2) those unable to tolerate primary resection, or (3) patients with tumors that are too locally invasive to allow excision. In such patients, a laser procedure with stent placement may improve airway patency and allow for other definitive treatments.

Preoperative details: Due to potential airway compromise, surgical intervention generally proceeds rapidly from time of diagnosis.

Intraoperative details: The surgical treatment of proximal airway tumors presents some technical challenges specifically related to the maintenance of acceptable ventilation beyond the area of obstruction. Techniques have been developed for distal intubation during the resection of the tumor. Percutaneous transtracheal ventilation has been used successfully for the laser endoscopic treatment of subglottic tumors.

Tumors of the upper-third of the trachea can be approached transcervically by a standard collar incision. Tumors in the middle-third of the trachea may require a partial or complete median sternotomy in addition to a cervical incision. Distal-third tumors are resected easily through a right thoracotomy to avoid the aortic arch.

Intraoperative bronchoscopy is used for accurate tumor localization. Lesions are resected with attempts to preserve as much trachea and lung tissue as possible. However, lobectomy may be necessary to ensure negative margins and node assessment. Using sleeve resections of the tracheal or bronchial tissue can preserve lung tissue.

Conventional wisdom has been that, at most, only 2 cm could be removed in order for the trachea to be reconstructed end-to-end dependably. Longer lesions are managed by lateral resection, leaving as wide a bridge of tracheal tissue as possible to maintain rigidity and patency of the airway. Because the defects usually are too large to be closed by suture, various materials are used as patches.

Prosthetic materials usually fail because the bed of mesenchymal tissue in which the foreign body lies becomes, in effect, a chronic ulcer and responds characteristically because it is adjacent to a contaminated epithelial surface. Granulation tissue then proliferates in an attempt to heal the area, producing obstruction or stricture. Migration of the prosthesis may lead to erosion of major vessels.

Complex reconstructions that use the patientís own tissues generally have been successful only in the neck, where delayed healing can be accepted and multistaged procedures are possible. Reconstruction in the mediastinum requires that a fully-fashioned rigid tube with an epithelial lining be present at conclusion of the initial operation.

Recent studies indicate that as much as half of the trachea can be removed and primary anastomosis achieved if extensive mobilization techniques are employed. These include (1) division of the inferior pulmonary ligament, (2) mobilization of the right mainstem bronchus from the pulmonary artery and vein and from the pericardium, and (3) release of the larynx by separation of its thyrohyoid attachments. Grillo has recommended using absorbable polyglactin (Vicryl) for all tracheal anastomoses to minimize granuloma formation. Usually, greater lengths of trachea may be removed in younger patients because of the greater elasticity of the trachea.

Follow-up care:

Benign lesions: Serial follow-up examination is recommended, especially if tracheal resection is not performed.

Malignant lesions: Follow-up examination similar to that for lung cancer is appropriate. Preoperative radiation is given for adenoid cystic carcinoma and adjuvant radiation for mucoepidermoid carcinoma. Consideration may be given to combined-modality therapy in carcinoid or other neuroendocrine tumors exhibiting more aggressive characteristics than the typical carcinoid lesions. Due to the infrequent nature of these tumors, most data are retrospective and series of outcomes are small.

Outcome

Median survival for all patients after diagnosis of malignant tracheal tumors is 6 months. Median survival varies widely with different histological types of tracheal tumors. Those who have adenoid cystic carcinoma or mucoepidermoid carcinoma have significantly better survival than those with other types of tumor. Following resection, carcinoid tumors carry excellent 5-year and 10-year survival rates in most series (95% and 90%, respectively).