Endobronchial metastases

CT findings of endobronchial metastases

During computed tomography (axial slice, lung window), endobronchial metastases, such as in colorectal cancer, are initially visualized as peribronchial nodules.

Of particular importance is the evaluation of the dynamics of the pathological process. As the disease progresses (which is well traced on CT reconstructions, e.g., 5 months after the initial study), a pronounced growth of the metastatic nodule is noted. This active increase in size leads to expansion of the affected bronchus and gradual filling of its lumen with tumor masses. A typical example of such localization is involvement of the superior segmental bronchus of the left lower lobe.

Differential diagnosis: Relapsing polychondritis

When performing differential diagnosis of endobronchial lesions, it is important to consider other systemic pathologies causing alterations of the airway walls. In relapsing polychondritis, axial slices (at the level of the distal trachea and main bronchi) reveal the following changes:

• Wall thickening: Pathological thickening of the anterior and lateral walls of the trachea, main bronchi, and the right upper lobe bronchus is observed.
• Calcification: Calcification or ossification (calcium salt deposits) is frequently present in the walls.
• Nature of involvement: The thickening can be focal or, much more commonly, diffuse, which inevitably leads to airway narrowing.

Key differential diagnostic feature: Unlike many other lesions, in relapsing polychondritis the posterior membranous wall of the trachea remains completely intact (unaffected).

Severe complications of this condition include the development of distal atelectasis, formation of bronchiectasis (or a combination thereof), and the onset of obstructive pneumonia due to narrowing of the proximal bronchi.

Differential diagnosis: Sarcoidosis

Airway sarcoidosis has specific radiological patterns that must be differentiated from endobronchial metastasis.

Tracheal involvement

This is relatively rare and usually associated with concurrent laryngeal involvement. Both proximal and distal segments of the trachea may be involved in the pathological process. The morphology of the resulting stenosis is variable: it can be smooth, irregular (nodular), or have a pronounced mass-like character (mass-like).

Bronchial involvement

This is a much more common manifestation of sarcoidosis. Main CT signs include:

• Uniform or nodular thickening of the bronchial walls, which histologically reflects the presence of sarcoid granulomas and fibrous tissue in the peribronchial interstitium.
• Smooth or irregular narrowing of the bronchial lumen (on bronchoscopy, this correlates with mucosal thickening and reflects a pronounced inflammatory process in the area).

Obstruction of lobar or segmental bronchi in sarcoidosis can result from granuloma proliferation, airway wall fibrosis, external compression by enlarged peribronchial lymph nodes, or conglomerate fibrosis (as well as a combination of these factors). It is important to note that bronchial stenosis in sarcoidosis has a favorable prognosis: it may resolve spontaneously or with adequate steroid therapy.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Features of lung window settings in CT evaluation of peribronchial changes
• CT semiotics of bronchiectasis and distal atelectasis in obstruction
• Morphological types of tracheal stenosis (smooth, nodular, mass-like)
• The role of bronchoscopy in verifying mucosal inflammatory changes in sarcoidosis

Other topics in the «Chest Radiology» section

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