Lungs
2. Findings and Diagnosis
72-year-old male with a history of asbestos exposure presents with a cough. Axial CTscan shows a magnified view of a pleural based nodule with a comet tail and a series of lung markings folded into the nodule. There is subsegmental compensatory hyperinflation of the lateral segment of the right lower lobe Noted pleural thickening and pleural based calcification which is reminiscent of asbestos related disease.
Ashley Davidoff MD TheCommonVein.net RnD 240Lu
Clinical Context
| Feature | Description |
|---|---|
| Age | 72-year-old male |
| Clinical Presentation | Chronic cough |
| Risk Factor | Known history of asbestos exposure |
| Imaging Modality | CT (lung and mediastinal windows) |
Radiologic Findings
| Finding | Description |
|---|---|
| Rounded opacity – RLL | Well-defined, peripheral, pleura-based mass-like opacity with air bronchograms |
| Pleural thickening | Localized adjacent pleural thickening, chronic in appearance |
| Pleural calcification | Densely calcified pleura, consistent with prior asbestos exposure |
| Comet tail sign | Curved bronchovascular bundles converging toward the opacity |
| Volume loss | Mild associated retraction of adjacent parenchyma |
Explanation of Radiologic Terms
| Term | Definition |
|---|---|
| Rounded Atelectasis | A form of collapsed lung that appears mass-like, often pleural-based |
| Pleural Thickening | Fibrotic or inflammatory thickening of the pleura, often from prior exposure |
| Pleural Calcification | Dense mineral deposits in the pleura, frequently from asbestos or old infections |
| Comet Tail Sign | Curved vessels and bronchi entering a peripheral lesion — typical of rounded atelectasis |
| Volume Loss | Retraction of lung tissue indicating chronic collapse or scarring |
Differential Diagnosis – Mass-like Opacity Adjacent to Calcified Pleura
Most Likely Diagnoses
| Disease Category | Specific Diagnosis |
|---|---|
| Mechanical | Rounded atelectasis from pleural scarring |
| Inflammatory/Immune | Post-inflammatory collapse and fibrosis |
| Infiltrative | Asbestos-related pleural disease |
Other Less Likely Considerations
| Disease Category | Specific Diagnosis |
|---|---|
| Neoplasm – Malignant | Bronchogenic carcinoma (peripheral, pleura-based) |
| Neoplasm – Metastatic | Pleural-based metastasis (rare without other nodules) |
| Infection | Healed TB with residual calcification and volume loss |
| Idiopathic | Idiopathic pleural fibrosis with associated collapse |
Key Points & Pearls
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Rounded atelectasis is a classic mimic of a peripheral lung mass, often seen in the setting of chronic pleural disease.
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Comet tail sign and adjacent pleural calcification are signature findings.
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Asbestos exposure predisposes to pleural fibrosis, calcification, and eventually rounded atelectasis.
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Differentiation from malignancy hinges on recognizing volume loss, pleural retraction, and vessel curving inward — not outward invasion.
3. Clinical
Page 4 – Info
Table 1. Clinical Definition and Context: Atelectasis (Rounded Type, Asbestos-related)
| Category | Details |
|---|---|
| What is it | A benign form of lung collapse resulting from pleural fibrosis, in which a portion of lung parenchyma becomes folded and entrapped, mimicking a peripheral mass. |
| Caused by | Chronic pleural inflammation and fibrosis, most commonly due to asbestos exposure, prior infection (e.g., TB), or hemothorax. |
| Resulting in | Folding of lung tissue toward thickened pleura → rounded, mass-like opacity with associated volume loss and vascular crowding. |
| Structural changes | Retraction of lung parenchyma, pleural thickening/calcification, curving of vessels (comet tail), fixed folding of bronchi and vasculature. |
| Functional changes | Usually minimal symptoms; small volume loss may cause mild dyspnea, though ventilation/perfusion mismatch is limited. |
| Diagnosis | Clinical: Often asymptomatic or mild cough. |
| Imaging: Rounded peripheral opacity, comet tail sign, adjacent pleural calcification. | |
| Other: Confirm history of asbestos or chronic pleural disease. | |
| Complications | Rare progression; may cause confusion with malignancy. Coexisting risks include mesothelioma or primary bronchogenic carcinoma from asbestos. |
| Treatment | No treatment required for the atelectasis itself. |
| Management includes education, imaging surveillance, and distinguishing from malignancy. |
5. MCQs
Page 6 – Multiple Choice Questions (MCQs)
Basic Science
Q1. Which of the following best explains the “comet tail sign” seen in rounded atelectasis?
A. Central necrosis of a neoplasm
B. Vessels and bronchi pulled into a folded, atelectatic lung segment
C. Calcified scar tissue trailing behind a lesion
D. Post-inflammatory lymphatic tracking
Correct Answer: B
Explanation: The comet tail sign represents curved bronchovascular bundles being pulled into a collapsed and folded lung segment by pleural scarring — a hallmark of rounded atelectasis.
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A: Seen in malignancy with cavitation.
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C: Describes calcification, not bronchovascular retraction.
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D: Lymphatic tracking is a pattern of interstitial disease.
Q2. What is the primary structural event that causes the lung to assume a “rounded” configuration in rounded atelectasis?
A. Airway dilation
B. Collapse around a central tumor
C. Pleural scarring and folding of adjacent lung parenchyma
D. Alveolar hemorrhage with secondary inflammation
Correct Answer: C
Explanation: Chronic pleural scarring leads to inward folding of lung parenchyma, producing a rounded, mass-like configuration.
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A, B, D: Do not produce a rounded contour with comet tail sign and pleural connection.
Clinical
Q3. A 72-year-old male with asbestos exposure has a CT showing a round peripheral opacity with comet tail sign and adjacent pleural calcification. What is the next best step?
A. CT-guided biopsy
B. PET scan
C. Bronchoscopy
D. Imaging follow-up and clinical observation
Correct Answer: D
Explanation: In the presence of classic imaging features, no intervention is needed. Follow-up imaging can confirm stability, distinguishing it from malignancy.
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A, B, and C: Not first-line in classic rounded atelectasis unless suspicious features are present.
Q4. Which of the following exposure histories most strongly supports the development of rounded atelectasis?
A. Smoking history of 40 pack-years
B. Childhood pneumonia
C. Occupational asbestos exposure
D. Tuberculosis contact without symptoms
Correct Answer: C
Explanation: Asbestos exposure is the most common risk factor for pleural fibrosis and rounded atelectasis.
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A: May predispose to carcinoma, not rounded atelectasis.
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B, D: Possible remote causes of pleural changes, but less specific.
Radiology
Q5. Which CT finding best differentiates rounded atelectasis from a peripheral neoplasm?
A. Size > 3 cm
B. Peripheral location
C. Smooth margins
D. Comet tail sign with pleural tethering
Correct Answer: D
Explanation: The comet tail sign, with vessels curving into a pleural-based mass, is characteristic of rounded atelectasis, not malignancy.
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A, B, and C: May be present in both entities and are not definitive.
Q6. Which imaging feature would raise suspicion that a “rounded opacity” is malignant rather than benign atelectasis?
A. Stability on serial imaging
B. Association with pleural calcification
C. Central cavitation
D. Comet tail sign
Correct Answer: C
Explanation: Cavitation, especially central and irregular, favors malignancy. Rounded atelectasis does not cavitate.
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A, B, D: All support benignity and stability.
Q7. Rounded atelectasis most commonly occurs in which lung zone?
A. Upper lobe apices
B. Perihilar central zones
C. Posterior and subpleural lower lobes
D. Lingula of the left lung
Correct Answer: C
Explanation: Rounded atelectasis typically involves posterior subpleural lower lobes, especially in gravity-dependent regions with adjacent pleural thickening.
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A, B, D: Not the usual location for this entity.
6. Memory Image
Page 7 – Memory Image
Memory Image Title:
“The Folded Fan of the Pleura”
Visual Concept (Metaphoric Illustration)
Imagine a Japanese paper fan, once fully open and extended, now gently closed by a tight cord.
The fan’s folds resemble pleural folds, and one section has curled in so tightly that it forms a rounded bulge at the base.
Inside, thin strings — like bronchovascular bundles — loop and curve, pulling inward, converging toward the base of the curl.
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The fan = the lung.
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The pleural cord = asbestos-induced fibrosis.
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The rounded base = the mass-like collapsed segment (rounded atelectasis).
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The curving strings = the “comet tail” sign — bronchi and vessels pulled inward.
Memory Caption (Learning Aid)
“When the pleura folds like a closing fan, the lung curls inward — curved vessels mark its path home.”
Key Learning Anchors from the Image
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Pleural scarring folds the lung — just as closing a fan retracts its segments.
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The mass-like contour is an illusion, created by mechanical folding, not neoplastic growth.
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The comet tail is a directional trail — bronchi and vessels pulled inward by chronic tethering.
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Helps learners distinguish a benign mimic from a dangerous mass through vivid shape analogy.