55 year old man for routine physical exam and chest radiograph. History of being an industrial worker.
Normal physical exam.
On PA and lateral radiographs, multiple 'holly leaf' appearing well circumscribed plaques are seen when viewed en face. When viewed in profile, the plaques appear squared off and linear, resembling a geologic "butte".
â€¢ PREVIOUS EMPYEMA - adjacent lung usually abnormal. scarring from previous pneumonia.
â€¢ MESOTHELIOMA - Unilateral, nodular thickening (>1cm), creeping mediastinal pleura and/or circumferential involvement. Nearly always associated with pleural effusion.
â€¢ PREVIOUS HEMOTHORAX - Unilateral, multiple healed rib fractures.
â€¢ METASTATIC ADENOCARCINOMA - Lobulated unilateral pleural thickening in patient with known malignancy; may be indistinguishable from mesothelioma.
â€¢ SUBPLEURAL FAT - Symmetric, mid-lateral chest wall 4th-8th ribs; may extend into fissures. Associated with other fat deposition: Pericardial fat pads, widened mediastinum; No calcification.
â€¢ PERIPHERAL BRONCHOGENIC CARCINOMA - may mimic rounded atelectasis. Spiculated outline (Not comet tail).
â€¢ RIB FRACTURES - Abnormal rib contour, posterolateral location
â€¢ SERRATUS ANTERIOR MUSCLE - Symmetric mid chest wall, between intercostal spaces; Triangular shape with edge fading inferiorly and no calcification.
Dx: Asbestos related pleural plaques
Dx Confirmed by: Radiographs combined with patient history
None. Benign process. Patient does not have lung based pathology. Patient to follow-up if symptoms present.
Asbestos is a silicate that exists in various forms, and more generically, in serpentine and amphibole form. The amphibole fibers are straight, rigid, and have a needle-like form. Examples include blue asbestos, amosite, actinolite, anthophyllite, tremolite, and crocidolite. The serpentine fibers are more common and account for over 90% of the asbestos used in the United States. Examples include chrysotile or white asbestos.
Adverse effects of asbestos became recognized in the United States in the 1970â€™s. There is a long latency period between exposure and time of onset of asbestos-related disease of 20 years or more. The disease spectrum includes more benign processes including pleural effusions, diffuse pleural thickening, rounded atelectasis, and pleural plaque formation. More serious spectra include asbestosis, mesothelioma, and lung cancer.
Asbestosis is defined as diffuse lung fibrosis due to inhalation of asbestos fibers.
Mesothelioma is a malignant pleural or peritoneal tumor that rarely occurs in patients who have not been exposed to asbestos.
All asbestos fibers cause a fibrogenic response.
Straight fibers such as the amphibole fibers, are not cleared from the lungs well, and can cause intense inflammation and fibrogenic changes within the lung interstitium. (1-4)
Conversely, serpentine fibers are flexible, do not fragment, and are longer, therefore, tend to be deposited in major airways, from which they are cleared to a large extent. They are also postulated to deposit more often in the pleura from lymphatic routes. Plaques grow slowly over time, even after cessation of exposure, but are not considered premalignant. (1-4,7)
Asbestosis tends to develop after a large exposure and long latency period. However, the pleura are more sensitive than the pulmonary tissue, and tend to form plaques after lower exposure to asbestos fibers. (1-4)
Pleural plaque formation is the most common manifestation of asbestos exposure. These form after a latent period of 20-40 years. Histologically, pleural plaques consist of acellular hyalinized collagen strands that form a basket-weave pattern and exclusively involve the parietal pleura. The plaques are more frequently associated with serpentine asbestos fibers than with amphibole fibers (6).
They are frequently bilateral symmetric, and occur on the posterolateral chest wall between ribs 5-8 , over mediastinal pleura, and on dome of diaphragm.(6)
Pleural plaques are frequently seen independently without evidence of any manifestations of asbestos-related disease. The opposite is not true, however. Asbestosis is rarely seen without plaque formation. (1-4)
Diffuse pleural thickening is less specific for asbestos exposure than is presence of pleural plaques since thickening can be seen in TB, hemothorax, and empyema. (1-4)
Benign asbestos-related pleural effusions are often the earliest manifestation of asbestos-related disease, usually occurring 10 years after exposure.
Effusions are exudative, and tend to be self-limiting, resolving in several months. These may be recur and become chronic.
Asbestosis is more often seen with amphibole fibers and occurs following a latent period of 15-20 years, with progression even after cessation of exposure. Fibrosis first arises in and around respiratory bronchioles, predominating in the subpleural portions of the lung in the lower lobes. (1-4,7)
Folded lung (aka round atelectasis, pulmonary pseudotumor, or Blesovsky syndrome) refers to atelectatic lung adjacent to pleural thickening, with characteristic in-drawing of bronchi and vessels. (1-5)
Mesothelioma is a rare neoplasm of the pleura, accounting for less than 5% of pleural malignancies. It is 80% pleural and 20% peritoneal in orgin.
Bronchogenic carcinoma is estimated to develop in 20-25% heavily exposed asbestos workers. Smoking history further increases this risk to a factor of 90.
After onset of symptoms, severe asbososis may lead to respiratory failure and death over 12-24 years.
Pleural plaques alone are usually benign and clinically asymptomatic.
Pleural plaques are not reported to cause symptoms. If symptomatic, patients may have complaints of dyspnea, pleuritic chest pain, elevated white blood cell count.
Diffuse pleural thickening â€“ dyspnea
Asbestosis â€“ insidious onset of progressive dyspnea and dry cough
Classic propensity for posterolateral, lateral, diaphgramatic and pericardial pleura; spares apices and costophrenic sulci.
Usually bilateral; if unilateral, preferentially the left hemithorax.
Rarely extends more than 4 rib interspaces. 2-5 mm thick.
Well demarcated but irregular elevations of pleura.
Linear band of calcification and squared shoulders when viewed in profile (butte shape); Irregular â€˜holly leafâ€™ when viewed en face.
Plaques are separated from rib by thin layer of fat
Plaque calcification seen in up to 15%
Size of individual plaques and extent of calcification increases with time.
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