Interstitial Pattern, Mediastinal-Hilar Adenopathy

Christopher M. Walker, MD

DIFFERENTIAL DIAGNOSIS

Common

Sarcoidosis
Lymphangitic Carcinomatosis
Cystic Fibrosis (Mimic)

Less Common

Silicosis/Coal Worker’s Pneumoconiosis
Usual Interstitial Pneumonia

Rare but Important

Berylliosis
Lymphocytic Interstitial Pneumonia
Diffuse Pulmonary Lymphangiomatosis
Pulmonary Langerhans Cell Histiocytosis
Lymphangioleiomyomatosis

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Age of patient
Gender
Race
Presenting symptoms

Helpful Clues for Common Diagnoses

Sarcoidosis
- Systemic granulomatous disease of unknown etiology
- Common demographics
  - Women
  - Child-bearing age
  - African-American race
- Radiography
  - Symmetric hilar and mediastinal lymphadenopathy
  - Mid to upper lobe reticulonodular opacities in ≤ 50% of patients
- HRCT
  - Bilateral hilar and mediastinal lymphadenopathy
  - Perilymphatic nodules involving fissures, subpleural lung, and bronchovascular bundles
  - Air-trapping secondary to granulomas obstructing small airways
Lymphangitic Carcinomatosis
- Tumor growth in pulmonary lymphatics
- Common causes include metastases from
  - Breast carcinoma
  - Bronchogenic carcinoma
  - Pancreatic carcinoma
  - Gastric carcinoma
  - Thyroid carcinoma
  - Adenocarcinoma of unknown primary
- Unilateral disease occurs most commonly with lung carcinoma
- Radiography
  - Reticulonodular opacities (unilateral or bilateral)
  - Hilar &/or mediastinal lymphadenopathy
  - Pleural effusions
- HRCT
  - Nodular or beaded interlobular septal thickening
  - Perilymphatic nodules
  - Hilar or mediastinal lymphadenopathy in 30-50% of patients
  - Pleural effusions
Cystic Fibrosis (Mimic)
- Autosomal recessive condition occurring primarily in Caucasians
  - Results in defective chloride transport across epithelial membranes
  - Causes variety of problems involving respiratory and gastrointestinal systems
- Radiograph
  - Large lungs with bronchiectasis or bronchial wall thickening mimicking interstitial pattern
  - Small peribronchovascular nodular opacities secondary to impaction of small airways
- Prominent hila indicate
  - Lymphadenopathy from recurrent infections
  - Enlarged pulmonary arteries from pulmonary hypertension
- Early disease predominates in upper lobes
- Uncontrollable hemoptysis may necessitate bronchial artery embolization

Helpful Clues for Less Common Diagnoses

Silicosis/Coal Worker’s Pneumoconiosis
- Radiography
  - Well-circumscribed small nodules predominating in upper lungs
  - Small percentage of pulmonary nodules may calcify
  - Nodules may coalesce to form masses with upward retraction of hila; so-called “progressive massive fibrosis”
  - Hilar lymphadenopathy
- HRCT
  - Centrilobular and subpleural nodules
  - Posterior upper lung predominance
  - 40% of patients have hilar or mediastinal lymphadenopathy
  - 5% of lymph nodes show peripheral “egg shell” calcification
Usual Interstitial Pneumonia
- Basilar and subpleural predominant fibrosis with honeycombing
- Mild mediastinal lymphadenopathy in majority of cases

Helpful Clues for Rare Diagnoses

Berylliosis
- Identical appearance to sarcoidosis
  - Perilymphatic nodules, lymphadenopathy, and noncaseating granulomas
  - Upper lung predominant disease
- Key discriminator is occupational exposure to beryllium
  - Workers in nuclear power, ceramics, aerospace, and electronics
  - Occurs most commonly 10-15 years after exposure
- Most common symptom is dyspnea
- Positive beryllium lymphocyte proliferation test via blood or bronchoalveolar lavage
Lymphocytic Interstitial Pneumonia
- Strong association with Sjögren syndrome
- AIDS defining in children
- Diffuse distribution
- Poorly defined centrilobular nodules
- Diffuse or patchy ground-glass opacity
- Isolated or diffuse cystic lung disease
- ± mediastinal or hilar lymphadenopathy
Diffuse Pulmonary Lymphangiomatosis
- Congenital lymphatic disorder
- Diffuse smooth interlobular septal thickening
- Mild mediastinal lymphadenopathy
- 50% have associated pleural effusions
Pulmonary Langerhans Cell Histiocytosis
- Young male smokers
- Radiography
  - Normal or large lungs
  - Nodular opacities in upper 2/3 of lung
  - Interstitial pattern results from “moire effect” of superimposed cysts
  - Pneumothoraces in 30% of cases
- HRCT
  - Bizarrely shaped cysts
  - Relative sparing of lung bases
  - Paracicatricial emphysema
  - Centrilobular nodules ± cavitation
Lymphangioleiomyomatosis
- Women of child-bearing age
- Radiography and HRCT
  - Pleural effusions
  - Pneumothoraces
  - Uniformly distributed similar-sized cysts
  - Interstitial pattern results from “moire effect” of superimposed cysts
  - Mediastinal or retroperitoneal lymphadenopathy