Adenoid cystic carcinoma of the trachea

Imaging features of adenoid cystic carcinoma

On computed tomography scans (at the level of the supra-aortic mediastinum), adenoid cystic carcinoma appears as a soft tissue mass growing from the posterior tracheal wall.

Specific visual signs:

• The tumor bulges directly into the airway lumen while maintaining an even, smooth surface.
• Sagittal reformations clearly demonstrate that in addition to the intraluminal component, the carcinoma actively extends posteriorly, forming a massive extraluminal growth.

This presentation requires careful evaluation of the process extension to surrounding mediastinal structures.

Differential diagnosis: other tumors

When detecting masses in the trachea and major bronchi, other neoplastic processes must be ruled out:

1. Atypical carcinoid tumor. Most commonly affects the bronchus intermedius or main bronchi, clinically manifesting with recurrent hemoptysis. On lung-window CT, it appears as a regular, rounded endobronchial mass. Following contrast administration (in mediastinal window), the carcinoid tissue strongly enhances. The tumor frequently causes bronchial obstruction with the development of peripheral atelectasis, and mucus-filled bronchiectasis may be visualized distal to the narrowing.
2. Benign tumors. Typically do not exceed 2 cm in diameter and appear as intraluminal polyps with smooth contours. A specific sign of hamartomas and lipomas is the presence of areas with fat tissue density.
3. Tracheobronchial papillomatosis. Caused by human papillomavirus (HPV), often transmitted at birth. The process originates in the larynx but can extend down into the trachea, proximal bronchi, and even the lung parenchyma. CT shows multiple small nodules within the lumen or diffuse nodular wall thickening. There is a risk of malignant transformation into squamous cell carcinoma.

Differential diagnosis: systemic diseases

A number of systemic pathologies can mimic a tumor lesion or cause airway stenosis:

• Granulomatosis with polyangiitis. Characterized by inflammatory foci, ulcerations, and pseudotumors. CT reveals smooth narrowing of the subglottic region and proximal trachea, as well as nodular lesions along the inner contour of the wall.
• Relapsing polychondritis. Autoimmune destruction of cartilage. In early stages, CT shows smooth wall thickening with luminal narrowing, while the posterior (membranous) wall remains intact. In late stages, the thickening becomes circumferential, and the trachea becomes flaccid and collapses during expiration. The outcome is persistent stenosis due to the destruction of cartilaginous rings and fibrosis.
• Tracheobronchial amyloidosis. Deposition of amyloid in the form of submucosal plaques or nodules. The overlying mucosa is unchanged; dystrophic calcification is typically associated.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Evaluation of atelectasis and bronchiectasis in bronchial obstruction of the bronchus intermedius (using carcinoid as an example).
• CT patterns of diffuse tracheal wall thickening in systemic vasculitides.
• Respiratory imaging biomechanics: expiratory tracheal collapse in polychondritis.
• The role of mediastinal and lung CT windows in visualizing endobronchial lesions.

Other topics in the «Chest Radiology» section

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