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Difficulty: MediumPathology and Biopsy Interpretation

A 65-year-old man presents to the pulmonology clinic for evaluation of progressive dyspnea on exertion and a dry cough that has worsened over the last year. He has a 30-pack-year smoking history but quit 5 years ago. Auscultation of the lungs reveals bibasilar end-inspiratory 'Velcro-like' crackles. Pulmonary function tests show a restrictive pattern with decreased diffusion capacity for carbon monoxide (DLCO). High-resolution computed tomography (HRCT) of the chest reveals peripheral reticular opacities and traction bronchiectasis, but the presence of honeycombing is equivocal. Due to the indeterminate HRCT pattern, a video-assisted thoracoscopic surgery (VATS) lung biopsy is performed.

The synoptic pathology report describes a patchy, heterogeneous fibrosing process. At low power, areas of dense collagenous fibrosis alternate with zones of relatively normal lung parenchyma. The fibrosis is primarily subpleural and paraseptal. High-power examination reveals discrete aggregates of proliferating fibroblasts and myofibroblasts (fibroblastic foci) at the interface between the dense scars and normal lung. There are no well-formed granulomas, eosinophilic infiltrates, or prominent intra-alveolar organizing exudates.

Based on the integration of the patient's clinical presentation and the histopathologic findings from the lung biopsy, which of the following is the most likely diagnosis?

  1. Idiopathic pulmonary fibrosisAnswer
  2. B
    Cryptogenic organizing pneumonia
  3. C
    Nonspecific interstitial pneumonia
  4. D
    Chronic hypersensitivity pneumonitis
  5. E
    Desquamative interstitial pneumonia

Answer

Idiopathic pulmonary fibrosis
The correct answer is Idiopathic pulmonary fibrosis (IPF). IPF is a chronic, progressive fibrosing interstitial pneumonia of unknown cause that occurs primarily in older adults. The diagnosis is confirmed by identifying the Usual Interstitial Pneumonia (UIP) pattern on high-resolution CT or surgical lung biopsy. The key pathologic hallmarks of UIP described in the vignette include: 1) patchy, alternating areas of normal lung, interstitial inflammation, fibrosis, and honeycomb change (spatial and temporal heterogeneity); 2) architectural distortion with subpleural and paraseptal predominance; and 3) fibroblastic foci (clusters of proliferating fibroblasts). The absence of granulomas or other specific features helps exclude alternative diagnoses.

Step-by-Step Solution

1
Analyze the clinical and radiologic presentation.
The patient has progressive dyspnea, crackles, a restrictive PFT pattern, and HRCT showing reticular opacities and traction bronchiectasis, suggesting an interstitial lung disease.
Establishing the clinical syndrome narrows the differential diagnosis to fibrosing interstitial pneumonias.
2
Interpret the lung biopsy findings.
The biopsy shows a patchy, heterogeneous fibrosing process with fibroblastic foci and alternating normal lung, lacking granulomas or organizing exudates.
This specific histopathologic description defines the Usual Interstitial Pneumonia (UIP) pattern.
3
Synthesize clinical and pathologic data to establish a diagnosis.
A confirmed UIP pattern on biopsy in a patient with this clinical profile, without an identifiable secondary cause, is diagnostic of Idiopathic pulmonary fibrosis.
IPF is the clinical syndrome characterized by the histopathologic pattern of UIP.

Key Concept

The diagnosis of Idiopathic Pulmonary Fibrosis requires integrating clinical features with the histopathologic Usual Interstitial Pneumonia (UIP) pattern, which is characterized by temporal and spatial heterogeneity and fibroblastic foci.
Estimated Time:1m 30s
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Topics

Pathology and Biopsy Interpretation

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