Rounded atelectasis and its association with asbestos-induced pleural disease

A Multimodality Imaging Review of Malignant Pleural Mesothelioma Response Assessment

Assessment of response is important to interpret early phase clinical trial results and to guide individual patient management. In malignant pleural mesothelioma (MPM), the circumferential growth pattern of the disease, the presence of pleural effusion and atelectasis, and the common use of pleurodesis make this a challenging task for imaging specialists and clinicians. This article reviews the current evidence for radiological and positron emission tomography (PET) response assessment in MPM, and the pitfalls and challenges in its application. Current research and future directions in radiological and PET response are discussed, including the use of novel radiotracers.

Rounded atelectasis of the lung

Rounded atelectasis of the lung (RA) is a lesion well described in the medical literature, yet often very difficult to diagnose. In recent years, the widespread use of high-resolution imaging modalities employed in the struggle against cancer, coinciding with the peak of the asbestos epidemic, have boosted the detection frequency of RA. However, its differential diagnosis still poses a challenge to the pulmonary specialist and the radiologist, as little is known about its pathogenesis. Furthermore, the multifactorial etiology of RA and its occasional coexistence with lung cancer make the task of confidently ruling out malignancy sometimes daunting. This article attempts to provide an update on RA's etiology, radiological evaluation, clinical management, and prognosis based on recent advances in broadly available diagnostic modalities and minimally invasive interventional procedures. An exemplary case of post-tuberculous RA is illustrated, as RA often presents as an unusual finding of a fairly common disease.

Imaging of thoracic occupational and environmental malignancies

The imaging features of occupational lung cancer are similar to those of nonoccupational cancer. Occupational lung cancer in patients with asbestos exposure must be differentiated from mimics such as round atelectasis and fissural pleural plaques. Mesothelioma remains a largely incurable tumor, though treatment options are expanding. CT, MRI, and PET scanning may all have complementary roles in staging mesothelioma.

The solitary pulmonary nodule: radiologic considerations

The solitary pulmonary nodule is a commonly encountered radiologic finding that might represent lung cancer, particularly in individuals at high risk to develop lung cancer. Morphological characteristics including lesion size, contour and edge, calcification and nodule density, and contrast enhancement may be helpful in the attempt to differentiate malignant from benign nodules. In certain instances, the combination of morphological characteristics indicates a specific diagnosis, sometimes precluding the need for further workup. Growth rate is of paramount importance in evaluating the nature of a solitary pulmonary nodule, and 2-year stability is traditionally considered an indicator of benignity. Screening for lung cancer using low-dose CT has led to the detection of small pulmonary nodules in a large number of high-risk individuals. In the workup of these nodules, lung cancer, when present, should be diagnosed as early as possible, while unnecessary surgery and needle biopsies should be avoided. Computer analysis may prove to be a valuable tool in the evaluation of these nodules.

CT and MR in pleural disease

A number of different imaging modalities can be used in the assessment of pleural disease. Although ultrasound has been the more traditional method, CT has found increasing utility for the assessment of the empyema and loculated pleural fluid collections prior to drainage and the evaluation of benign and malignant pleural tumors. MRI has a limited but important role particularly in the evaluation of focal pleural tumors such as lipomas and in determining the extent of malignant mesothelioma prior to therapy.

Ultrasound features of folded lung

The ultrasound features of folded lung (rounded atelectasis) have not been described previously. The US findings of folded lung in fourteen patients and correlation with computed tomography are presented. The principal US findings were a pleurally based 'mass' and thickening of the adjacent pleura and extrapleural fat. A highly echogenic line extending from the pleural surface into the mass was seen in 12 patients (86%). We believe this finding corresponds to the scarred invaginated pleura as demonstrated in pathological studies of this condition.

Asbestos-related rounded atelectasis. Radiologic and mineralogic data in 23 cases

A retrospective study was conducted in 23 subjects with previous occupational exposure to asbestos and exhibiting rounded atelectasis (RA) on high-resolution computed tomography scan (HRCT scan) to evaluate the retention of asbestos bodies (ABs) using light microscopy in the bronchoalveolar lavage (BAL) fluid or lung parenchyma in such patients. A total of 31 RAs were identified, usually located in the lower (25 RAs) and posterior (23 RAs) parts of the lung. Pleural thickening in contact with the RA was observed in 27 RAs and parenchymal bands were detected in 15 cases. Twelve of the 20 patients who underwent BAL or surgery exhibited significant retention of ABs in BAL fluid or lung tissue. Moreover, a significant retention of ABs was observed in five of nine patients with a history of asbestos exposure but no diffuse pleural thickening on chest radiograph or interstitial opacities on HRCT scan. Patients with RAs and coexisting diffuse pleural thickening and/or interstitial fibrosis should be considered at a higher risk for lung cancer in comparison to patients with isolated circumscribed pleural plaques based on increased AB counts. By contrast, the excess risk of lung cancer is more questionable in patients with only RAs and circumscribed pleural plaques as they may have AB counts either above or below that associated with pleural plaques alone. This emphasizes the need for further follow-up studies to define criteria indicating the need for thoracotomy in these subjects.

Round atelectasis and Metsovo lung

Round (helical) atelectasis is one of the benign sequelae of occupational asbestos exposure. Environmental asbestos exposure does not differ from occupational in its pleural manifestations, but to our knowledge, round atelectasis has not been reported yet. In the present study, we present the clinical and radiologic findings of five individuals with round atelectasis. They were all born in the Metsovo area, northwest Greece, where environmental exposure to asbestos (tremolite) has been documented. All five had negative evaluation for malignancy. In addition, they have been followed up for one to four years and four of them are in good health, thus confirming round atelectasis as a benign, nonpremalignant condition. The fifth patient died of malignant pleural mesothelioma two years later, while the previously detected round atelectasis remained unchanged. We therefore consider that his mesothelioma was not related to the round atelectasis, although both were certainly related to the same environmental asbestos exposure.

CT appearances of rounded atelectasis

Five patients examined with CT had lesions fulfilling criteria for a diagnosis of rounded atelectasis (RA) and these were managed without biopsy. In three patients unsuspected contralateral lesions were identified as RA variants, and one of these was biopsied at thoracotomy and proved to be benign. All patients remain well at 6-22 months follow-up. We concur with recent reports that there is a spectrum of CT appearances of RA and that even atypical lesions seldom need further investigation. We also suggest that the appearances of some atypical lesions add support for the fibrosing theory of pathogenesis of RA.

Rounded atelectasis: diagnosis by fine-needle aspiration cytology

Rounded atelectasis, a rare, benign mass lesion, is most often seen in association with asbestos-related pleural changes. Often a presumptive diagnosis can be made on the basis of characteristic CT and chest radiographic findings. However, not infrequently radiographic imaging fails to differentiate rounded atelectasis from primary bronchogenic carcinoma, a disease which is seen with increased frequency in patients with asbestos exposure. We describe two cases where the diagnosis of rounded atelectasis was made by fine-needle aspiration (FNA) cytology. The cytologic features included abundant pulmonary parenchymal material with thickened alveolar walls containing pulmonary macrophages and connective tissue. It is important to realize that this is a useful positive finding indicating rounded atelectasis, rather than a negative finding suggesting the absence of neoplasm. Needles with a cutting action may be necessary to obtain sufficient material to make the diagnosis of rounded atelectasis.

Rounded atelectasis: a pulmonary pseudotumor

Rounded atelectasis is a benign entity that is often misinterpreted as a pulmonary neoplasm. The roentgenologic appearance of a mass is due to an infolding of atelectatic tissue intermingled with pleura, blood vessels, and bronchi. Rounded atelectasis is usually asymptomatic and is commonly associated with chronic pleural disease or pleural effusions. The distinctive radiologic features include a rounded, pleural-based opacity associated with adjacent pleural thickening and volume loss of the affected lobe. The pathognomonic sign is the "comet tail" that results from the crowding of vessels and bronchi as they enter the atelectatic region. Many authors consider this constellation of findings diagnostic. Rounded atelectasis usually remains stable over time; however, slow growth, as well as diminution in size, has been described. A retrospective analysis revealed 7 cases of rounded atelectasis at our institution over a 9-year period. Three were operated on to exclude malignancy, one was confirmed at operation performed for other reasons, and 3 were followed up expectantly. We conclude that recognition of this entity and its radiologic features can be diagnostic and render further workup, including thoracotomy, unnecessary.

Asbestos-related chest diseases: plain radiographic findings

In summary, there are a wide range of pulmonary manifestations seen in asbestos-exposed individuals from pleural and parenchymal fibrosis to pleural and parenchymal malignancy. The chest roentgenogram has assumed an important role in the detection and surveillance of asbestos-related pleural and parenchymal changes.

Asbestos induced pericardial effusion and constrictive pericarditis

The number of disorders attributable to asbestos exposure has increased gradually over the years. The latest to be recorded is pericardial effusion and constrictive pericarditis, and three cases are reported here. A man with bilateral pleural thickening and plaques developed acute pericarditis and an effusion and was treated by pericardiectomy. Two men died from constrictive pericarditis associated with bilateral pleural effusions and diffusion pleural thickening. The pericardium showed nonspecific fibrous thickening. All had been occupationally exposed to asbestos. In the fatal cases the lungs contained amphibole fibres, in keeping with a modest degree of occupational exposure. Asbestos produces progressive fibrosis of the pericardium that is similar to diffuse pleural thickening and may be fatal. Both conditions may develop after relatively short or light exposure.

Rounded atelectasis complicated by obstructive pneumonia and pulmonary arterial thrombosis

A patient with a history of asbestos exposure developed rounded atelectasis. The mass was associated with local bronchial obstruction, obstructive pneumonia and arterial thrombosis. Autopsy demonstrated marked pleural thickening and radiographically inapparent asbestosis. This is the first reported case in which seemingly benign rounded atelectasis not only increased morbidity, but also contributed to mortality through airway obstruction and local arterial thrombosis.

Computed tomography of folded lung

Computed tomography (CT) scans of 22 examples of folded lung in nine patients were reviewed. The most important CT criteria of folded lung are the presence of vessels and bronchi running in a smooth curvilinear fashion towards a peripheral mass with an ill defined central edge associated with pleural thickening. These features were seen in all 22 examples. The lesions are frequently multiple (eight out of nine patients). When these features are present the diagnosis can be made without recourse to biopsy or thoracotomy. Enhancement with intravenous contrast medium is unnecessary and does not provide any extra useful information. Various other previously described criteria such as air bronchograms are not necessary for the diagnosis.

Shrinking pleuritis with lobar atelectasis, a morphologic variant of "round atelectasis"

Round atelectasis (shrinking pleuritis) is typically a localized process characterized by focal pleural scarring and subjacent peripheral atelectasis. We report three patients, studied at autopsy, with an unusual variant of round atelectasis, termed shrinking pleuritis with lobar atelectasis, which is characterized by lobar atelectasis, visceral pleural fibrosis involving multiple lobes, interlobar fibrous cords, pleural effusion, and nonspecific, persistent infiltrates on chest radiogram. The possible causes of shrinking pleuritis with lobar atelectasis in our patients were multiple and included environmental dust exposure, infection, uremia, and recurrent pleural effusions. Our findings support both the folding (pleural effusion) and fibrosing (pleural injury) theories of pathogenesis of round atelectasis and emphasize the spectrum of morphologic variability in this condition.

An unusual case of rounded atelectasis

An unusual case of rounded atelectasis (RA) is described. This entity is likely to develop as a consequence of asbestos-induced pleural disease. The sine qua non of RA is a curvilinear tail extending from the inferior medial surface of a peripheral mass. Recognition of this "comet tail" prevents the necessity for surgery.

Rounded atelectasis due to acute exudative effusion. Spontaneous resolution

Rounded atelectasis is an interesting roentgenographic entity that must be distinguished from intrathoracic neoplasm. Chronic pleural disease, particularly that due to asbestos exposure, is a frequently cited cause, and is considered to be a sine qua non by some. We report a case of rounded atelectasis with an acute parapneumonic exudative effusion that resolved spontaneously with roentgenographically normal pleura.

Malignant pleural mesothelioma: the role of computed tomography

Computed tomography is believed to have a definite role in the evaluation of malignant pleural mesothelioma based on a review of computed tomography findings in 23 of our patients and previous reports. Twelve patients had a single computed tomography examination, and 11 had two or more studies. Computed tomography permits better appreciation of the extent of the tumor. This permits appropriate selection of therapy and may demonstrate that surgery or radiotherapy is not indicated. computed tomography often permits more accurate evaluation following chemotherapy and may be the only means by which to follow a patient after radical surgery. Computed tomography also has a role in differential diagnosis. It facilitates distinction of malignant pleural mesothelioma from rounded atelectasis, pleural changes of asbestosis, and pleural involvement with lymphoma and thymoma. It aids, but may not be diagnostic, in separating malignant pleural mesothelioma from metastases to the pleura.

Computed tomographic diagnosis of rounded atelectasis: a case report

A case of rounded atelectasis of the lung is presented in which the diagnosis was made following computed tomography. This imaging technique enabled differentiation of this benign condition from other causes of lung masses. In certain cases where diagnosis is difficult by conventional means, CT may prove helpful and prevent unnecessary surgery.

Computed tomographic features of round atelectasis

Computed tomography (CT) of the chest is often variable in the evaluation of pulmonary masses. Our case demonstrated characteristic findings on CT that aided in the diagnosis of round atelectasis.