Tracheal neoplasm

Tracheal neoplasms, Table 1. Tracheal neoplasm classification.

A tracheal mass grows silently until it narrows the airway lumen by 75%; dyspnoea, cough, stridor, wheezing and haemoptysis are the most common presenting complaints. These signs and symptoms may be misdiagnosed as asthma or bronchitis and the tumour may elude detection for months to years. Posteroanterior and lateral chest radiographs that use high kilovoltage technique and adequate penetration of the mediastinum may reveal lesions large enough to create symptoms. CT displays both the intraluminal portion of the mass and extraluminal extension. Spiral volumetric acquisition permitting multiplanar and three-dimensional reformatted images enables good assessment of the extent of the tumour, particularly along the long axis of the trachea, and helps in planning treatment and following the treatment response.

Benign neoplasms are less frequent than their malignant counterparts. They include papillomatosis, pleomorphic adenomas and primary mesenchymal tumours such as hamartomas (Table 1). They all tend to be well circumscribed, smoothly marginated, rounded and less than 2 cm in diameter. On CT scans, the mass is intraluminal and limited by the tracheal cartilage (Fig.1). The presence of fat within an endotracheal mass allows a definitive diagnosis of hamartoma (see hamartoma pulmonary). Identification of calcium within the mass usually indicates a cartilaginous lesion.

Primary malignant neoplasm accounts for less than 1% of all chest malignancies. The most common tumours are squamous cell carcinoma (Fig.2), and pulmonary adenoid cystic carcinoma. Less common neoplasms include carcinoid and mucoepidermoid tumours. CT and MR are particularly valuable in detecting extratracheal extension, through direct invasion of adjacent tissue or metastases to regional lymph nodes. Up to 10% of these malignant tumours are circumferential.

Most malignant tumours present with an irregular surface and are usually 2–4 cm in size. On CT, a tracheal malignancy usually appears as a soft tissue mass within the tracheal wall, often sessile, eccentric and arising from the posterior and lateral wall. Due to its vascular nature, carcinoid tumour may show marked enhancement on CT scans obtained after intravenous injection of contrast material. Bronchoscopy establishes the diagnosis and identifies the mucosal and intraluminal portions of the lumen.

Malignant neoplasms may secondarily involve the trachea through direct extension or metastases. The most common malignancies that locally invade the trachea include cancer of the thyroid, oesophagus, larynx and lung. Haematogenous metastases to the tracheal mucosa are rare. The most common sources are melanomas, breast cancers and malignancies of the genitourinary tract. On CT scans, the lesions usually appear as polypoid soft tissue masses that are generally solitary but may be multiple.

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