Rounded Atelectasis RLL Pleural thickening Hyperinflated Posteriorly Positioned Segment in RLL Bilatera Pleural Calcification Note also Early Rounded atelectasis in the LLL Bilateral Fat Proliferation
Rounded Atelectasis (aka Folded Lung Syndrome) and Asbestos Related disease 72-year-old male with a history of asbestos exposure presents with a cough. Axial CTscan using lung windows, shows a pleural based nodule (purple arrowhead b) with a subtending curvilinear comet tail formed by a trailing bronchovascular bundle (teal blue b). There is associated pleural thickening and pleural based calcification (black arrowheads ,b), reminiscent of asbestos related disease. Ashley Davidoff MD TheCommonVein.net 118433cL 240Lu
Finding
Definition
Comment
Rounded Atelectasis
A form of peripheral lung collapse that occurs adjacent to a thickened, scarred pleura.
It is characterized by the infolding of visceral pleura.
This condition is strongly associated with asbestos exposure.
On CT, it presents as a peripheral, rounded or oval-shaped opacity in contact with the pleura, often with volume loss in the affected lobe.
A characteristic finding is the “comet tail sign,” where distorted bronchi and vessels are pulled into the opacity.
Hillerdal G, et al., Radiology, 1981
Pleural Thickening
An increase in the thickness of the visceral or parietal pleura.
It can be focal, nodular, or diffuse and may occur due to benign or malignant processes.
In the context of asbestos exposure, diffuse pleural thickening is a common finding and is considered a form of benign asbestos-related pleural disease.
It often appears as a continuous sheet of thickening, which can involve the costophrenic angles.
It is a distinct entity from the more circumscribed pleural plaques.
Gevenois PA, et al., Eur Respir J, 1998
Pleural Calcification
The deposition of calcium within the pleura, often occurring in areas of chronic pleural thickening or pleural plaques.
Asbestos-related pleural calcifications typically manifest as calcified pleural plaques.
These plaques are most commonly found on the parietal pleura, particularly along the posterolateral chest wall and diaphragmatic domes, and are considered a specific marker of asbestos exposure.
The costophrenic angles are often spared.
Rocha R, et al., J Bras Pneumol, 2017
Early rounded atelectasis in the LLL
As above
As above
Compensatory hyperinflation of a posterior segment of the RLL
The overinflation of unaffected parts of a lung to compensate for volume loss in another part of the same lung or the contralateral lung.
This phenomenon is a common consequence of conditions that cause lung volume loss, such as atelectasis or surgical resection.
The presence of hyperinflation can be a helpful indirect sign of underlying atelectasis.
Madan K, et al., BMJ Case Reports, 2013
Bilateral pleural fat proliferation
An increase or proliferation of the normal subpleural or extrapleural fat layer.
This fat is located in the loose connective tissue layer of the pleura, external to the parietal pleura.
This finding is a marker of a chronic inflammatory pleural process.
In the context of asbestos exposure, it can be a response to chronic pleural irritation and may mimic non-calcified pleural plaques.
Its presence is a strong indicator that the associated pleural disease is benign.
Sargent EN, et al., Radiology, 1984
Rounded Atelectasis (aka Folded Lung Syndrome) and Asbestos Related disease 72-year-old male with a history of asbestos exposure presents with a cough. Axial CTscan using soft tissue windows, shows a pleural based nodule with a comet tail and exemplifying the bilateral pleural thickening and pleural based calcification reminiscent of asbestos related disease. Ashley Davidoff MD TheCommonVein.net RnD 240Lu
Rounded atelectasis, also known as folded lung or Blesovsky syndrome, is a distinct form of peripheral lung collapse where a portion of the lung involutes and folds upon itself, adjacent to an area of thickened pleura.
It represents a benign condition that can radiologically mimic a malignant neoplasm, such as lung cancer.
Cause
The most common cause is asbestos-related pleural disease, which is implicated in a high percentage of cases.
Other etiologies are related to conditions causing chronic pleural inflammation and fibrosis, including other mineral dust exposures, congestive heart failure, parapneumonic effusions, tuberculosis, pulmonary infarction, and post-surgical or post-traumatic hemothorax.
Pathophysiology
The predominant theory suggests that a chronic pleural effusion or local pleuritis incites inflammation, leading to visceral pleural fibrosis and thickening.
As the pleural fluid resolves and the fibrous tissue contracts, it exerts traction on the adjacent lung parenchyma.
This process causes the lung to fold in on itself, entrapping parenchyma and creating the characteristic rounded shape. The visceral pleura invaginates into the lung, leading to the atelectasis.
Structural result
Gross pathology demonstrates localized, dense fibrosis and thickening of the visceral pleura.
The underlying lung parenchyma is collapsed and folded, with invagination of the pleura.
Histopathology reveals nonspecific findings, including collapsed alveoli, fibroelastic pleural thickening, and chronic inflammation. The folded pleura contains normal vascular and lymphatic structures. In cases of asbestos exposure, asbestos bodies may be identified.
Functional impact
Rounded atelectasis is frequently asymptomatic and discovered incidentally on imaging.
When symptoms such as a non-productive cough, dyspnea, or chest pain occur, they are often attributable to the underlying pleural disease (e.g., asbestosis) rather than the atelectasis itself.
Pulmonary Function Tests (PFTs) may be normal if the lesion is isolated and there is no extensive pleural or parenchymal disease. In the presence of diffuse pleural thickening or asbestosis, a restrictive ventilatory defect may be observed.
Imaging
Computed Tomography (CT) is the imaging modality of choice for diagnosis.
Characteristic findings include a peripheral, round or oval-shaped soft tissue mass that abuts a thickened pleura.
The pathognomonic feature is the ‘comet tail sign,’ which represents the swirling and convergence of bronchovascular bundles curving towards the lesion.
Other associated findings include ipsilateral pleural thickening, pleural plaques (which may be calcified), and volume loss in the affected lobe.
Labs
There are no specific laboratory studies that diagnose rounded atelectasis.
Laboratory findings are generally normal or reflect the underlying etiology.
Arterial blood gas may show hypoxemia if the atelectasis is extensive or associated with significant underlying lung disease. Lab tests may be utilized to help exclude differential diagnoses such as infection or malignancy.
Treatment
As a benign and typically stable entity, rounded atelectasis does not require specific treatment.
Management is focused on conservative observation with follow-up imaging to confirm stability over time.
Invasive procedures, such as transthoracic needle biopsy or video-assisted thoracoscopic surgery (VATS), are reserved for diagnostically equivocal cases where malignancy cannot be confidently excluded based on imaging characteristics. Surgical intervention is rarely required unless there is severe functional impairment or high suspicion of cancer.
Prognosis
The prognosis for rounded atelectasis itself is excellent, as it is a benign condition with no known malignant potential.
The lesion typically remains stable in size over long-term follow-up.
The patient’s overall prognosis is determined by the underlying etiology, particularly the presence and severity of associated asbestos-related conditions like asbestosis, diffuse pleural thickening, or the increased risk for developing malignant mesothelioma or lung cancer.
The term “atelectasis” is derived from the Greek words atelēs, meaning “incomplete,” and ektasis, meaning “expansion.” This literally translates to “incomplete expansion” of the lung.
“Asbestos” originates from the Ancient Greek word ἄσβεστος (asbestos), meaning “unquenchable” or “inextinguishable.” This name was given due to the mineral’s remarkable fire-resistant properties.
AKA / Terminology
Rounded atelectasis is also known as “folded lung,” “Blesovsky syndrome,” or “atelectatic pseudotumor.”
The term “folded lung” was notably described by A. Blesovsky in 1966.
Pleural plaques are sometimes referred to as hyaline pleural plaques due to their composition of cartilage-like hyaline collagen.
Pneumoconiosis is the general term for interstitial lung disease caused by the inhalation of dust.
Historical Notes
Asbestos has been used for over 4,500 years, with ancient civilizations like the Egyptians and Greeks valuing its fire-resistant properties. It was used in items such as burial shrouds, tablecloths, and lamp wicks.
The modern asbestos industry began in the late 19th century, with mass production of products like insulation, fireproof coatings, and construction materials.
The first documented case of asbestos-related disease was in 1906, and the term “asbestosis” was first used in 1927 to describe lung fibrosis in an asbestos textile worker.
The link between asbestos exposure and lung cancer was suggested by E.R.A. Merewether in the 1930s and 1940s, though it was not widely accepted until later.
Dr. Irving J. Selikoff’s research in the 1960s was groundbreaking, definitively linking asbestos exposure to mesothelioma and other cancers, and highlighting the risks of even brief or indirect exposure.
Pleural plaques are the most common manifestation of asbestos exposure, with a latency period of 20 years or more. Their calcification is a later finding.
Rounded atelectasis was first described by Loeschke in 1928, and later more comprehensively by Blesovsky in the context of asbestos exposure.
Cultural or Practice Insights
Asbestos was once marketed as a “magic mineral” due to its versatility and seemingly miraculous properties of being fireproof and indestructible. Advertisements targeted farmers and homeowners, promoting its use for creating durable and safe buildings.
The perception of asbestos shifted dramatically from a “miracle mineral” to a deadly hazard as the health risks became undeniable, largely due to the work of researchers like Dr. Selikoff.
The asbestos industry actively worked to downplay the health risks, funding their own research and opposing warning labels.
The long latency period of asbestos-related diseases, often 20 to 50 years, contributed to the delayed public and regulatory response.
The societal impact has been immense, with hundreds of thousands of deaths annually attributed to occupational asbestos exposure, and ongoing risks from asbestos remaining in older buildings.
Notable Figures or Contributions
Pliny the Elder: A Roman naturalist who noted the fireproof qualities of asbestos but also observed that slaves working in asbestos mines suffered from a “sickness of the lungs.”
H. Montague Murray: In 1899, he was the first to report on the “curious bodies” in the lungs of an asbestos worker. In 1906, he documented the first recorded death from asbestos-related lung failure.
William Edmund Cooke: He published a detailed report on a case of asbestosis in 1924 and 1927, describing the pathological changes in the lungs.
E.R.A. Merewether: A British factory inspector who, in the 1930s, conducted a study that proved the link between asbestos exposure and asbestosis, leading to the first asbestos industry regulations. He later also highlighted the increased risk of lung cancer.
A. Blesovsky: A surgeon who, in 1966, described the “folded lung” in patients with pleural thickening, a condition now often referred to as Blesovsky syndrome.
Dr. Irving J. Selikoff: A pivotal figure whose research in the 1960s established the definitive link between asbestos exposure and a range of deadly diseases, including mesothelioma, even with low levels of exposure. His work was instrumental in raising public awareness and leading to stricter regulations.
Quotes and/or Teaching Lines
Quote from Dr. Irving J. Selikoff: “Statistics are people with the tears wiped away.” This quote emphasizes the human cost behind the epidemiological data of asbestos-related diseases.
Quote from Dr. Irving J. Selikoff: “If we have learned anything from the tragic experience of asbestos,” Selikoff said, “it is that we must look with a skeptical eye at substances introduced into the environment before their toxicity is fully understood.”
Teaching Line for Radiology: The “comet tail sign” on CT, representing the curving of bronchovascular bundles toward a peripheral lung mass, is a pathognomonic feature of rounded atelectasis.
Teaching Line for Radiology: The presence of the “crow’s feet sign,” which are linear bands radiating from the mass into the lung parenchyma, is another characteristic finding of rounded atelectasis.
Teaching Line for Radiology: In the context of asbestos exposure, the presence of pleural plaques, particularly if calcified and involving the diaphragmatic pleura, strongly supports the diagnosis of an asbestos-related condition.
Teaching Line for Radiology: Differentiating rounded atelectasis from a peripheral lung carcinoma is crucial; the stability of the lesion over time on follow-up imaging is a key distinguishing feature.
A Poem of the Folded Lung
From mines of old, a magic dust, In “unquenchable” fibers, we placed our trust. A shield from fire, a builder’s dream, A silent threat, it would now seem.
Decades pass, a cough takes hold, A story in the lungs, bravely told. The pleura thickens, a calcified line, A history of exposure, a telling sign.
A shadow forms, a rounded mass, Where lung has folded, time won’t let it pass. The “comet’s tail” on CT’s screen, A vascular swirl, a historic scene.
Not cancer’s rage, but a benign fold, A tale of asbestos, now grown old. Blesovsky’s name, a syndrome’s grace, A folded lung in this hallowed space.
1. What is the fundamental pathophysiologic mechanism by which asbestos fibers lead to pleural fibrosis and plaque formation?
2. While all forms of asbestos are fibrogenic and carcinogenic, which type is most strongly associated with the development of malignant mesothelioma due to its physical properties?
3. A 72-year-old male with a history of occupational asbestos exposure presents for evaluation. Which of the following clinical findings is most characteristic of asbestosis?
4. According to current general recommendations, what is an appropriate screening strategy for an individual with a significant history of asbestos exposure (e.g., >5 years) and a concurrent smoking history?
5. On a chest CT, which of the following is considered the pathognomonic sign for rounded atelectasis?
6. What is the most common and characteristic location for asbestos-related pleural plaques as seen on CT imaging?
7. In a patient with a history of asbestos exposure presenting with a peripheral rounded opacity adjacent to thickened pleura, what is the most important differential diagnosis to exclude?
Part B
1. What is the fundamental pathophysiologic mechanism by which asbestos fibers lead to pleural fibrosis and plaque formation?
a) Direct cytotoxic effect on mesothelial cells leading to necrosis and calcification.
❌
While asbestos can be toxic to cells, the primary mechanism for fibrosis is not direct necrosis but a prolonged inflammatory response.
b) Activation of a chronic inflammatory cascade involving macrophages and the release of fibrogenic cytokines.
✔️
Inhaled asbestos fibers that reach the pleura are recognized as foreign bodies, activating an immune response.
This leads to chronic inflammation, with macrophages releasing profibrotic mediators like transforming growth factor-beta (TGF-β), which stimulates collagen deposition and results in fibrosis and plaque formation.
Mossman BT, Nat Rev Cancer, 2013
c) Encapsulation of fibers by a foreign body giant cell reaction, which then undergoes malignant transformation.
❌
Foreign body giant cells are part of the inflammatory response, but their primary role here is containment, not direct malignant transformation.
Malignancy (mesothelioma) is a separate, though related, pathologic process.
d) Obstruction of pleural lymphatics, causing chronic pleural effusions and subsequent fibrinous organization.
❌
While asbestos can cause benign pleural effusions, lymphatic obstruction is not considered the principal mechanism for the formation of focal, hyalinized pleural plaques.
The process is more directly related to parenchymal and pleural inflammation.
2. While all forms of asbestos are fibrogenic and carcinogenic, which type is most strongly associated with the development of malignant mesothelioma due to its physical properties?
a) Chrysotile
❌
Chrysotile is a serpentine fiber and is the most commonly used type.
While it is a carcinogen, its curly fibers are more easily cleared from the lungs compared to amphibole fibers, making it less potent in causing mesothelioma than crocidolite.
b) Crocidolite
✔️
Crocidolite, an amphibole (straight, needle-like) fiber, is considered the most dangerous type of asbestos in terms of mesothelioma risk.
Its physical structure allows it to penetrate deeper into the lung tissue and persist, causing prolonged irritation and damage to mesothelial cells.
Kamp DW, J Thorac Dis, 2020
c) Anthophyllite
❌
Anthophyllite is an amphibole fiber but is less commonly associated with mesothelioma compared to crocidolite and amosite.
d) Tremolite
❌
Tremolite is an amphibole fiber that can be a contaminant in other minerals like talc.
It is associated with mesothelioma, but crocidolite is recognized as having the highest risk.
3. A 72-year-old male with a history of occupational asbestos exposure presents for evaluation. Which of the following clinical findings is most characteristic of asbestosis?
a) Progressive dyspnea, inspiratory crackles, and digital clubbing.
✔️
Asbestosis is a form of interstitial pulmonary fibrosis.
Its classic presentation includes the insidious onset of shortness of breath on exertion, bibasilar end-inspiratory crackles on auscultation, and in more advanced cases, digital clubbing.
American Thoracic Society, Am J Respir Crit Care Med, 2004
b) Acute-onset pleuritic chest pain and a unilateral pleural effusion.
❌
This presentation is more typical of a benign asbestos pleural effusion (BAPE), which can occur after asbestos exposure but is a distinct entity from the parenchymal fibrosis of asbestosis.
c) Chronic productive cough, wheezing, and evidence of airflow obstruction on spirometry.
❌
These are hallmark features of Chronic Obstructive Pulmonary Disease (COPD), which is primarily associated with smoking, not asbestosis.
Asbestosis typically causes a restrictive, not obstructive, pattern on pulmonary function tests.
d) Fever, weight loss, and hilar adenopathy.
❌
While weight loss can occur in severe disease, this constellation of symptoms, particularly fever and hilar adenopathy, is more concerning for malignancy (like lung cancer or mesothelioma) or an infectious/granulomatous disease like tuberculosis.
4. According to current general recommendations, what is an appropriate screening strategy for an individual with a significant history of asbestos exposure (e.g., >5 years) and a concurrent smoking history?
a) Annual chest radiography only.
❌
Chest X-ray is less sensitive than LDCT for detecting early-stage lung cancer and is no longer the recommended primary modality for lung cancer screening.
b) Spirometry every 2 years.
❌
Spirometry is used to assess lung function and can help diagnose conditions like asbestosis (restrictive defect) or COPD, but it is not a screening tool for detecting lung cancer.
c) Annual low-dose computed tomography (LDCT) of the chest.
✔️
Given that asbestos exposure and smoking have a synergistic effect on lung cancer risk, individuals with a significant history of both are at very high risk.
Guidelines support offering annual LDCT screening to high-risk individuals, including those with significant occupational asbestos exposure combined with a history of smoking.
Moyer VA; U.S. Preventive Services Task Force, Ann Intern Med, 2014
d) No routine screening is indicated unless symptoms develop.
❌
Waiting for symptoms (like cough, weight loss) often means the cancer is at an advanced, less curable stage.
Screening is designed to detect the disease at an early, asymptomatic stage to improve outcomes.
5. On a chest CT, which of the following is considered the pathognomonic sign for rounded atelectasis?
a) Air bronchograms within a peripheral mass.
❌
Air bronchograms can be seen in various conditions, including pneumonia, lymphoma, and some types of lung cancer.
While they can be present in rounded atelectasis, they are not the specific diagnostic sign.
b) “Holly leaf” sign of pleural plaques.
❌
The “holly leaf” sign describes the appearance of calcified pleural plaques, which are often seen in the same patient population, but it is not a sign of rounded atelectasis itself.
c) Homogeneous ground-glass opacity in a lobar distribution.
❌
This finding is nonspecific and more commonly associated with infection (like pneumocystis pneumonia), pulmonary edema, or diffuse alveolar hemorrhage.
d) “Comet tail” sign showing swirling of bronchovascular structures toward the lesion.
✔️
The “comet tail” sign is the classic and most specific imaging feature of rounded atelectasis.
It is created by the swirling and pulling of the bronchovascular bundle as it curves towards the collapsed, rounded lung parenchyma, which is trapped by thickened, fibrotic pleura.
McHugh K, Br J Radiol, 1991
6. What is the most common and characteristic location for asbestos-related pleural plaques as seen on CT imaging?
a) Apical and perihilar regions.
❌
The lung apices and costophrenic angles are typically spared by asbestos-related pleural plaques.
b) Visceral pleura exclusively.
❌
Pleural plaques predominantly arise from the parietal pleura (the lining of the chest wall), not the visceral pleura (the lining of the lung itself).
Diffuse pleural thickening, a separate entity, can involve the visceral pleura.
c) Parietal pleura of the posterolateral chest wall and along the diaphragm.
✔️
The most frequent locations for pleural plaques are on the parietal pleura, particularly along the posterolateral aspects of the 6th through 9th ribs, and on the diaphragmatic pleura.
Peacock C, Br Med Bull, 2000
d) Costophrenic sulci and interlobar fissures.
❌
The costophrenic sulci (angles) are characteristically spared.
While the interlobar fissures can sometimes be involved, it is not the most typical location.
7. In a patient with a history of asbestos exposure presenting with a peripheral rounded opacity adjacent to thickened pleura, what is the most important differential diagnosis to exclude?
a) Organizing pneumonia.
❌
While organizing pneumonia can present as a peripheral opacity, it is less common in this specific clinical context and is not the primary concern that must be ruled out, especially given the risk factors.
b) Lung abscess.
❌
A lung abscess would typically present with clinical signs of infection (fever, chills), be centrally necrotic with an air-fluid level, and have a different appearance than the smooth, folded look of rounded atelectasis.
c) Bronchogenic carcinoma.
✔️
Given that asbestos exposure is a significant risk factor for lung cancer, any peripheral mass-like lesion in an exposed individual must be carefully evaluated to exclude a primary bronchogenic carcinoma, which can mimic rounded atelectasis.
Differentiating these two entities is of paramount clinical importance.
Hillerdal G, Eur Respir J, 1994
d) Pulmonary infarction.
❌
A pulmonary infarct typically appears as a wedge-shaped, pleura-based opacity and is associated with clinical signs of pulmonary embolism.
While it is in the differential, it is a less likely masquerader than lung cancer.
He built the ships in days gone by, Beneath a clouded, dusty sky. He breathed the fibers, sharp and fine, A fateful dust from the assembly line.
Now years have passed, the CT shows The silent mark that exposure sows: A plaque of white, a chalky scar, On pleura’s lining, near and far. A calcified and hardened shield, A toxic history revealed.
But see the lung, it takes a turn, A painful lesson he must learn. The thickened pleura pulls and grips, And part of his own lung tissue slips. It folds right in, a rounded mass, Trapped in a slow, fibrotic pass.
No tumor, but a “folded lung,”From shipyard songs, so long unsung. The builder and his legacy, Are written on his own decree: The plaque, the fold, the price he paid, From the asbestos dust he braved.
A fateful dust from the assembly line.
From shipyard songs, so long unsung.