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Difficulty: MediumPathology and Biopsy Interpretation

An accountant in his late fifties is referred for specialized pulmonary evaluation due to worsening dyspnea on exertion and a persistent, dry cough that has developed gradually over the past twelve months. He denies any history of tobacco use, occupational exposures to dust or chemicals, or keeping birds as pets. Auscultation of the chest reveals fine, 'Velcro-like' end-inspiratory crackles at both lung bases. Following a chest radiograph and high-resolution computed tomography scan that demonstrate peripheral reticular opacities with subpleural honeycombing, a video-assisted thoracoscopic surgical lung biopsy is obtained to definitively establish the diagnosis. The resulting surgical pathology report notes a temporally and spatially heterogeneous appearance at low magnification. The tissue exhibits alternating zones of preserved alveolar architecture, dense collagenous fibrosis with architectural remodeling, and loose organizing connective tissue representing fibroblastic foci. Microscopic examination confirms the absence of granulomas, viral inclusions, and ferruginous bodies. Based on this histopathologic interpretation, which of the following is the most likely diagnosis?

  1. A
    Cryptogenic organizing pneumonia
  2. Idiopathic pulmonary fibrosisAnswer
  3. C
    Hypersensitivity pneumonitis
  4. D
    Nonspecific interstitial pneumonia
  5. E
    Asbestosis

Answer

Idiopathic pulmonary fibrosis
The correct answer is Idiopathic pulmonary fibrosis because the biopsy describes the classic histopathologic features of a Usual Interstitial Pneumonia (UIP) pattern. The hallmark of UIP is a highly heterogeneous appearance (both temporally and spatially) featuring alternating areas of normal lung tissue, dense established fibrosis with honeycomb change, and active loose connective tissue known as fibroblastic foci. When this specific histologic pattern is found in a patient without an identifiable underlying cause, the definitive clinical diagnosis is Idiopathic pulmonary fibrosis.

Step-by-Step Solution

1
Identify the key histopathologic pattern described in the surgical lung biopsy report.
The report describes alternating zones of normal lung, dense fibrosis, and fibroblastic foci, which defines the Usual Interstitial Pneumonia (UIP) pattern.
Establishing the specific morphologic pattern is the foundational step in diagnosing and categorizing interstitial lung diseases.
2
Rule out secondary or exposure-related causes of the UIP pattern based on the provided pathology and clinical history.
The absence of ferruginous bodies rules out asbestosis, and the lack of granulomas or bird exposure rules out chronic hypersensitivity pneumonitis.
The UIP pattern can be caused by collagen vascular diseases or specific environmental exposures, which must be systematically excluded before confirming an idiopathic etiology.
3
Correlate the idiopathic UIP pattern with the clinical syndrome to establish the final diagnosis.
The definitive diagnosis is Idiopathic pulmonary fibrosis.
Idiopathic pulmonary fibrosis is clinically defined by the presence of a UIP pattern on imaging or histology in the strict absence of a known alternative cause.

Key Concept

Recognizing the histopathologic features of the Usual Interstitial Pneumonia (UIP) pattern—specifically temporal and spatial heterogeneity with fibroblastic foci—is essential for diagnosing Idiopathic Pulmonary Fibrosis when secondary causes are absent.
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Topics

Pathology and Biopsy Interpretation

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