round atelectasis is a rare lung pseudotumor that is most commonly associated with asbestos - related disease but it may arise from a variety of chronic pleural conditions such as infection , uremia or heart failure and is usually asymptomatic . although round atelectasis has typical radiological features , it sometimes mimics carcinoma clinically and histologically , posing a diagnostic challenge for the clinician and leading to unnecessary surgical resection . our observations suggest that clinicians should consider sarcoidosis in the differential diagnosis of diseases leading to round atelectasis . the four patients were under follow up for previously diagnosed sarcoidosis at our outpatient clinic . all subjects underwent pulmonary function tests , diffusion capacity and arterial blood gases assessment and thoracic computerized tomography ( ct ) prior to the bronchoscopic procedures . fiberoptic bronchoscopy , bronchoalveolar lavage ( bal ) and transbronchial lung biopsy were performed in each patient . a 38-year old male with a four - year history of sarcoidosis presented with posterior thoracic pain . there was no history of previous occupational or environmental asbestos exposure , infection or pleural disease . he was a smoker ( 24 pack / years ) and did not use any medication . ct revealed an oval pleural based opacity associated with loss of volume , curving of adjacent pulmonary vessels and bronchi into the edges of the opacity at the level of right lower lobe with bronchovascular and subpleural nodules ( figure 1 ) . bronchoscopic examination and broncho alveolar lavage cytology were normal with no asbestos bodies and with negative cultures for bacteria , fungus or mycobacteria . ct image at the level of the right lower lobe bronchus shows an oval mass abutting the pleura , pulmonary vessels curving toward the opacity with parenchymal nodules . an asymptomatic 46-year old male with a two - year history of sarcoidosis presented with dry cough . personal and family history were negative with no history of previous infection , or asbestos exposure . he was a smoker ( 32 pack / years ) with no use of medication . hemogram , liver enzymes , serum creatinine and blood urea nitrogen ( bun ) were within the reference values . chest ct revealed a round mass at the level of the right lower lobe with the characteristic comet tail sign of curving of bronchi and pulmonary vessels into the lesion with bronchovascular and subpleural nodules ( figure 2 ) . chest ct revealed a round pleural - based mass at the level of the right lower lobe with the characteristic comet tail sign of curving of vessels into the lesion with peribronchovascular and subpleural nodules . the patient was a smoker ( 30 pack / years ) and did not use any medication . ct revealed a peripheral lentiform mass at the level of the right lower lobe abutting the pleura posteriorly with curving of adjacent pulmonary vessels and bronchi into the edges of the opacity . a 39-year old asymptomatic male presented with a subpleural lentiform lesion with smooth margins on the chest x - ray during his routine control for sarcoidosis . the patient had had sarcoidosis for 6 years and was a smoker ( 20 pack / years ) with no previous use of medication . chest x - ray showed a left irregular mass of 2 cm abutting the pleura posteriorly . ct revealed a rounded mass adjacent to an area of pleural thickening with a vessel curving into its lateral aspect . a 38-year old male with a four - year history of sarcoidosis presented with posterior thoracic pain . there was no history of previous occupational or environmental asbestos exposure , infection or pleural disease . he was a smoker ( 24 pack / years ) and did not use any medication . ct revealed an oval pleural based opacity associated with loss of volume , curving of adjacent pulmonary vessels and bronchi into the edges of the opacity at the level of right lower lobe with bronchovascular and subpleural nodules ( figure 1 ) . bronchoscopic examination and broncho alveolar lavage cytology were normal with no asbestos bodies and with negative cultures for bacteria , fungus or mycobacteria . ct image at the level of the right lower lobe bronchus shows an oval mass abutting the pleura , pulmonary vessels curving toward the opacity with parenchymal nodules . an asymptomatic 46-year old male with a two - year history of sarcoidosis presented with dry cough . personal and family history were negative with no history of previous infection , or asbestos exposure . he was a smoker ( 32 pack / years ) with no use of medication . hemogram , liver enzymes , serum creatinine and blood urea nitrogen ( bun ) were within the reference values . chest ct revealed a round mass at the level of the right lower lobe with the characteristic comet tail sign of curving of bronchi and pulmonary vessels into the lesion with bronchovascular and subpleural nodules ( figure 2 ) . chest ct revealed a round pleural - based mass at the level of the right lower lobe with the characteristic comet tail sign of curving of vessels into the lesion with peribronchovascular and subpleural nodules . the patient was a smoker ( 30 pack / years ) and did not use any medication . ct revealed a peripheral lentiform mass at the level of the right lower lobe abutting the pleura posteriorly with curving of adjacent pulmonary vessels and bronchi into the edges of the opacity . a 39-year old asymptomatic male presented with a subpleural lentiform lesion with smooth margins on the chest x - ray during his routine control for sarcoidosis . the patient had had sarcoidosis for 6 years and was a smoker ( 20 pack / years ) with no previous use of medication . chest x - ray showed a left irregular mass of 2 cm abutting the pleura posteriorly . ct revealed a rounded mass adjacent to an area of pleural thickening with a vessel curving into its lateral aspect . patients with round atelectasis are predominantly male and are often smokers , with a mean age of 60 years , range 20 to 83 years . although most cases are attributed to asbestos exposure , the other potential etiologies are tuberculosis , uremia , heart failure , and dressler syndrome and trauma . a specific etiology was not elicited from the clinical history or laboratory investigations of our patients who were all under follow up for previously diagnosed sarcoidosis . round atelectasis may be the result of the mechanical influence of a pleural effusion on the lung with folding of the parenchyma or a primary localized inflammation of the pleura may become progressively fibrotic and contract , leading to folding of the pleura and collapse of the lung . transient pleural effusion or a localized pleural inflammation associated with sarcodosis may have led to round atelectasis in our patients as the above theories have suggested . the overall low prevalance of pleural effusion - the predominant mechanism for round atelectasis - in sarcodosis ( less than 2% ) may be the explanation for the lack of previously reported round atelectasis associated with sarcoidosis in the medical literature . asymptomatic disease course , spontaneous remission occuring in 85% of the sarcoidosis patients , asymptomatic presentation or the incidental finding of pleural effusion   and the probable spontaneous regression of round atelectasis   may be the other factors associated with the underdiagnosis of round atelectasis in sarcodosis . the chest ct in these four cases had typical features but there was no specific etiology to explain the formation of round atelectasis in our patients , e.g. asbestos exposure , chronic pleural disease or infection history . the laboratory or the clinical findings was not compatible with an etiologic cause for round atelectasis either . as there are no descriptions of sarcoidosis presenting with round atelectasis in the literature , the patients underwent fiberoptic broncho scopy with transbronchial lung biopsy for the diagnosis of the peripheral lesions . we conclude that round atelectasis may occur as a result of previous pleural effusion or a primary localized pleural involvement in sarcoidosis . although chest ct may reveal the typical radiologic features of the lesion , round atelectasis may appear as a diagnostic challenge for the clinician because there are no previous reports of round atelectasis associated with sarcoidosis . our cases suggest that clinicians should consider sarcoidosis as a potential etiologic factor for round atelectasis . further studies are needed to define the real incidence of round atelectasis among patients with sarcoidosis because the sample size of our report is small . the safety and the high diagnostic yield of transbronchial lung biopsy establishes this technique as a viable alternative for obtaining adequate tissue samples for round atelectasis due to sarcoidosis . none of the authors has any conflict of interest to declare in relation to the subject matter of this manuscript .
round atelectasis is a benign inflammatory condition most frequently observed in patients with asbestos exposure but it can also result from a variety of chronic pleural diseases like infection . 
 it has not previously been described in sarcoidosis . 
 we report the occurrence of round atelectasis in four previously diagnosed sarcoidosis patients who were under follow up at our outpatient clinic . 
 three patients had symptoms consisting of thoracic pain , dry cough and sensation of fullness at the posterior thorax , respectively . 
 chest roentgenogram showed subpleural or pleural based opacity with diameters ranging from 2 to 3 cm in each of the patients . 
 chest computerized tomography ( ct ) revealed features of round atelectasis . 
 fiberoptic bronchoscopy with transbronchial lung biopsy was performed . 
 diagnosis was confirmed by the histopathologic examination of the biopsy samples . the mechanical influence of a prior pleural effusion due to sarcoidosis may be the predominant mechanism underlying the onset of round atelectasis in these patients . 
 clinicians should bear in mind the possibility of sarcoidosis as an etiologic factor for round atelectasis .