Focal Tracheobronchial Wall Thickening

Christopher M. Walker, MD

DIFFERENTIAL DIAGNOSIS

Common

Mucus
Bronchial Neoplasm

Less Common

Airway Stenosis
Carcinoid

Rare but Important

Metastasis
Foreign Body
Tracheal Neoplasm
Infection
Wegener Granulomatosis
Fibrosing Mediastinitis
Broncholith
Tracheobronchial Amyloidosis

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Review focuses on diseases causing solitary/segmental wall thickening or nodularity
Age of patient, smoking history, and history of malignancy are important considerations

Helpful Clues for Common Diagnoses

Mucus
- Common in emphysema, asthma, bronchitis, or cystic fibrosis
- “Bubbly” or solid appearance on CT
- Gravity-dependent location
- Repeat CT after vigorous coughing helpful to differentiate from tumor
Bronchial Neoplasm
- Bronchogenic carcinoma
  - Polypoid nodule with endobronchial and extraluminal components
  - Postobstructive pneumonia/atelectasis
  - ± mediastinal and hilar lymphadenopathy
  - ± history of recurrent pneumonia
- Hamartoma
  - Round and smooth nodule
  - ≤ 2 cm in diameter
  - ± internal fat
  - ± “popcorn” calcifications
- Mucoepidermoid carcinoma
  - Intraluminal nodule
  - 50% of patients are ≤ 30 years old
  - Difficult to differentiate radiographically from carcinoid and bronchogenic carcinoma

Helpful Clues for Less Common Diagnoses

Airway Stenosis
- Progressive dyspnea following extubation or tracheostomy tube placement
  - Focal airway narrowing with circumferential wall thickening
  - Hourglass appearance
- Prolonged endotracheal intubation
  - Subglottic narrowing at balloon cuff site
- Tracheostomy tube
  - Stenosis at stoma site
- Complete cartilaginous tracheal ring is an anomaly
- Sarcoidosis; look for other typical features
Carcinoid
- Round or ovoid lobulated nodule
- Occurs in lobar or segmental bronchi
- ± intense contrast enhancement
- 25% demonstrate chunky calcification
- 80% are “typical”
  - Benign and slow growing
  - Metastases and carcinoid syndrome rare

Helpful Clues for Rare Diagnoses

Metastasis
- Invasion or compression from lymphoma, bronchogenic, thyroid, or esophageal carcinoma
  - Adjacent airway mass readily apparent
- Hematogenous metastases from melanoma, breast, colon, or renal cell carcinoma
  - ± solitary or multiple endobronchial nodules
  - Lymph node metastases may cause airway compression
Foreign Body
- Most are radiolucent on radiographs
- Easily mistaken for malignancy
- History of aspiration and recurrent pneumonia
Tracheal Neoplasm
- Squamous cell carcinoma
  - Most common primary tracheal neoplasm
  - 33% have mediastinal or pulmonary metastases at diagnosis
  - 40% with past, present, or future carcinoma of oropharynx, larynx, or lung
  - Irregular-shaped polypoid or sessile lesion
  - Predominates in lower trachea
- Adenoid cystic carcinoma
  - Submucosal or circumferential wall thickening
  - ± long tracheal segment involvement
  - Disease recurs locally
  - Metastases are rare
Infection
- Tuberculosis
  - Distal trachea and proximal bronchi
  - Irregular circumferential wall thickening
  - Tracheal narrowing
  - Secondary to “endobronchial spread” or extension from involved lymph nodes
  - Infection rarely isolated to trachea
- Histoplasmosis
  - Endobronchial nodule or mass
  - ± calcified mediastinal lymph nodes
  - ± apical cavitary nodules
- Rhinoscleroma
  - Endemic in Central America, Africa, and India
  - 95% have nasal polyps and soft tissue thickening
  - Paranasal sinuses spared
  - Concentric or nodular subglottic tracheal narrowing in 25%
  - Air-filled tracheal crypts nearly diagnostic
Wegener Granulomatosis
- 25% have airway involvement
  - Circumferential subglottic tracheal wall thickening
  - ± luminal narrowing
- ± cavitary lung nodules
- ± pan-sinus disease
- Laboratory evidence of glomerulonephritis (microscopic hematuria, red cell casts, and proteinuria)
Fibrosing Mediastinitis
- Common associations
  - Histoplasmosis, tuberculosis, or sarcoidosis (unilateral)
  - Retroperitoneal fibrosis, drugs, or autoimmune disorders (bilateral)
- Mediastinal fat replaced by fibrous tissue
- Encases and narrows adjacent structures
  - Superior vena cava, mainstem bronchi, pulmonary artery, or esophagus
- ± mediastinal or hilar lymph node calcification
Broncholith
- Irregularly shaped calcified material within airway arising from adjacent calcified lymph node
- ± extraluminal air
- Right middle and upper lobe bronchi
- No contrast enhancement
Tracheobronchial Amyloidosis
- Most common presentation is multifocal nodular deposits throughout central airways
- Single submucosal nodule is extremely rare