The gamut of cystic lung disease: a practical approach to differential diagnosis

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1 The gamut of cystic lung disease: a practical approach to differential diagnosis Award: Cum Laude Poster No.: P-0100 Congress: ESTI 2014 Type: Educational Poster Authors: C. Leal, R. Santos, J. P. A. Lopes, P. Ananias, N. Costa, H. M. R. Marques, R. Santos, O. Fernandes, L. Figueiredo ; 1 2 Lavradio/PT, Lisbon/PT Keywords: Education and training, Cysts, Education, Diagnostic procedure, CT-High Resolution, CT, Conventional radiography, Thorax, Lung DOI: /esti2014/P-0100 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 49

2 Learning objectives - To review the definition of a lung cyst. - To differentiate a lung cyst from other lesions capable of simulating a cyst, like an emphysematous bulla, cystic bronchiectasis, honeycombing, a cavitating malignancy or a different type of lung cavity. - To present and illustrate the whole range of causes of cystic lung disease. - To emphasize the radiological and clinical key points to differentiate the pathologies. Page 2 of 49

3 Background High Resolution Computed Tomography (HRCT) of the lung is an important modality in the evaluation of interstitial lung disease including cystic lung disease. Pulmonary cysts should first of all be differentiated from other entities (like emphysema, bronchiectasis and fibrosis), the various causes of pulmonary cavities (malignant, infectious, inflammatory, vascular, traumatic - "cavity" mnemonic) and pseudocavities given the differing prognostic implications. Fig. 1 References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT When they are identified on computed tomography, they require explanation (an underlying reason for their existence should be sought). Page 3 of 49

4 Unlike in other solid organs, the lungs do not develop so-called simple cysts. With the exception of centrilobular emphysema, pulmonary diseases characterized by cystic air spaces are uncommon or rare conditions. The mechanisms leading to cyst formation are very much speculative in nature and include a ball-valve effect causing bronchial dilatation, focal pulmonary necrosis and retractile fibrosis. The differential diagnosis for diseases characterized by lung cysts is broad ranging from isolated chest disorders to rare multisystem diseases. Fig. 2 References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 4 of 49

5 First of all, we need to exclude other entities that may simulate cystic lung involvement. Fig. 3 References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 5 of 49

6 Fig. 4 References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 6 of 49

7 Fig. 5 References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Centrilobular emphysema- This type of emphysema is most common in patients with a history of cigarette smoking and is distributed predominantly in the upper lobes. Pulmonary destruction begins in the center of the secondary pulmonary lobule, but as the disease progresses the entire secondary pulmonary lobule becomes involved. So, the interlobular septa between the destroyed lobules may appear to be the walls of a cyst. Because the destruction occurs centrally in the secondary pulmonary lobule, the centrilobular artery is typically visible in the center of the lucent area rather than eccentrically. In a lung cyst, the centrilobular artery is either not visible or is displaced and therefore seen eccentric. In emphysema, the lucent area preserves the polygonal shape of the secondary pulmonary lobule, whereas cysts are typically perfectly rounded or sometimes irregularly shaped. Paraseptal emphysema- Involves the most distal aspect of the secondary pulmonary lobule and is most commonly seen as a single row of elongated, thin-walled, air-filled Page 7 of 49

8 structures distributed along the subpleural region. It may occur in nonsmokers and has a predominant subpleural distribution. Panlobar emphysema - It is classically associated with #1-antitrypsin deficiency, but it may also occur in smokers or elderly patients or in association with illicit drug use. The pulmonary parenchymal destruction is distributed evenly throughout the secondary pulmonary lobule and involves the lung parenchyma diffusely or is most severe in the lower lobes. A bulla is defined as a sharply demarcated area of emphysema that is #1 cm in diameter and that has a wall that is #1 mm thick.bullae are located in the subpleural region rather than within the lung parenchyma and are a manifestation of paraseptal emphysema, although they can also occur in centrilobular emphysema. Fig. 6 References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 8 of 49

9 Fig. 7 References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Bronchiectasis most commonly occurs secondary to recurrent pulmonary infections, but it may also occur in association with hereditary syndromes, such as cystic fibrosis, dysmotile cilia syndrome and Williams-Campbell syndrome, as well as in immunodeficiency disorders, connective tissue diseases and pulmonary fibrosis (traction bronchiectasis). Bronchiectasis can be distinguished from pulmonary cysts by following the dilated airways on multiple sequential chest CT scan images, which will show a branching pattern that is usually better visualized on the coronal and sagittal reformatted images Page 9 of 49

10 Fig. 8 References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT End-stage pulmonary fibrosis and honeycombing have multiple rows of air-filled spaces clustered in the subpleural region, predominantly in the lower lobes. These spaces vary in size, shape and wall thickness but are typically <1 cm in diameter. Other signs of pulmonary fibrosis may be seen, such as decreased lung volumes, reticular opacities, architectural distortion and traction bronchiectasis. Page 10 of 49

11 Fig. 9 References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Also, congenital cystic diseases of the lung are a rare but significant cause of morbidity in children and young adults presenting with respiratory distress and repeated chest infections that can simulate cystic lung involvement. Page 11 of 49

12 Fig. 10 References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Congenital cystic adenomatoid malformations It present as cystic or solid lung masses restricted to part of one lung. Most present with respiratory distress or compromise during infancy or recurrent pneumonias in later years, including adulthood. The pathological feature of CAMs is adenomatoid proliferation of the bronchioles that forms a cyst at the expense of alveoli. Three types of CAMs are recognized based on cyst size, number, and pathology. Type 1 consists of multiple large cyst (2#10 cm), at least one cyst will be dominant with smaller cysts seen along its periphery. The cyst wall is lined with ciliated pseudostratified Page 12 of 49

13 columnar epithelium, contains elastic tissue beneath the epithelium, smooth muscle, and fibrovascular connective tissue, including cartilage. Type 2 consists of small and more uniform size cysts (0.5#2 cm). They are lined with cuboidal to columnar epithelium and have only a thin fibromuscular wall. This type has associated anomalies - renal, cardiac, skeletal, intestinal, extra#lobar sequestration. Type 3 lesions are bulky solid lesions that usually involve entire lobe of the lung. There is slight modification of the classification of CCAM with now five types being recognized out of which only three types are identified on imaging as mentioned above. It is now called as congenital pulmonary airway malformations since all the types are not cystic. Additional types are, Type 0, which has either no cyst or very small ones (<0.5 cm), and is incompatible with life and Type 4 CCAM which consists of large cysts up to 10 cm in size. Congenital lobar emphysema Is a disease that causes breathing difficulties in newborn or infants. Exact etiopathogenesis is still a dilemma, however, changes in bronchial cartilage have known to occur in most cases. On chest X#ray, there is over inflation of the diseased lobe resulting in shift of mediastinum to contralateral side and compression of ipsilateral lung with attenuation of vascular markings. CT findings help to confirm these findings. CLE is commonly associated with congenital heart disease such as ventricular septal defect and patent ductus arterirous. Differential diagnosis includes CCAM, pulmonary hypoplasia, and pnuemothorax. Treatment includes lobectomy of affected lung. Pulmonary sequestration It is a disorder characterized by a non-functioning lung parenchyma, which does not communicate with tracheo-bronchial tree and receives blood supply from systemic artery. Sequestration is believed to be due to abnormal budding of primitive foregut. Anatomically it can be classified as intra-lobar and extra-lobar sequestration. Page 13 of 49

14 Clinically, sequestration present as recurrent pneumonia in adults and adolescents, in case of intra-lobar and respiratory distress, chronic cough in infancy, in case of extralobar sequestration. Intra-lobar sequestration lies within visceral pleura and usually located in posterobasal segment of the lung. Arterial supply is from abdominal aorta or thoracic aorta and venous drainage through pulmonary veins into left atrium. It communicates with adjacent lung parenchyma through pore of Kohn, which allows infection to occur and resolution is incomplete or slow due to inadequate bronchial drainage. Extra-lobar sequestration is surrounded by its own pleura, usually located on the left side of the lower chest. It is usually associated with other congenital anomalies like diaphragmatic hernia, congenital heart disease, and CCAM. Radiologically sequestration on a chest radiograph demonstrated by a soft-tissue opacity in chest base. Bronchi ecstasies, cystic areas, sub-segmental atelectasis, mediastinal shift, and prominence of ipsilateral hila are other radiological findings that arise due to recurrent infection. CT scan show cystic areas containing air or fluid, focal emphysema, and atelectasis. The arterial supply and venous drainage, which are pathognomic features of sequestration are better demonstrated by contrast enhanced CT scan. Bronchogenic cysts Arise from abnormal budding of the tracheobronchial tree during airway development. This abnormal bud subsequently differentiates into a fluid#filled blind#end pouch. More often present in the mediastinum, one third can occur in the lung parenchyma, usually within the lower lobes. These cysts may contain air, fluid, or both. Clinical manifestations are related to various mass effects or secondary infection of the cyst. Intrapulmonary bronchogenic cyst are rare (14%), most of them are fluid attenuating. Only 36% of intrapulmonary bronchogenic cyst contains air, which occurs when the cyst communicates with the bronchial tree. Their radiographic appearance is as a sharply defined, solitary, uncalcified round or oval density presenting as one of three categories: A cyst with a homogeneous density filled with fluid, an air-filled cyst or a cyst containing air and fluid. Page 14 of 49

15 Images for this section: Fig. 1 Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 15 of 49

16 Fig. 2 Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 16 of 49

17 Fig. 3 Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 17 of 49

18 Fig. 4 Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 18 of 49

19 Fig. 5 Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 19 of 49

20 Fig. 6 Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 20 of 49

21 Fig. 7 Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 21 of 49

22 Fig. 8 Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 22 of 49

23 Fig. 9 Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 23 of 49

24 Fig. 10 Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 24 of 49

25 Imaging findings OR Procedure details There are disorders in which the HRCT findings can be diagnostic. However, frequentlythe appearances on CT are more non-specific and integration with clinical and/or histopathological information is crucial. Important clues to the differential diagnosis are: - Age and sex of the patient - Distribution of the cysts - Cyst shape and size - Presence of any ancillary CT findings Also, we can have three different CT scenarios: -Multiple diffuse pulmonary cysts Lymphangioleiomyomatosis, Langerhans cell histiocytosis and centrilobular emphysema -Scattered pulmonary cysts with ancillary CT signs Lymphocytic interstitial pneumonia, hypersensitivity pneumonitis and desquamative interstitial pneumonia -Scattered cysts or the incidental lung cyst with no ancillary CT features 1 - Multiple diffuse pulmonary cysts Langerhans cell histiocytosis(lch) Langerhans cell - Dendritic cell, found in many organs. Proliferation and organ infiltration of these cells results in either single or multi-organ disease. Page 25 of 49

26 - Pulmonary involvement develops most commonly in isolation - Occurs in young patients, between the ages of 20 and 40 years - Almost all are cigarette smokers - Patients may be asymptomatic or present with dyspnoea. Less frequently presenting complaints include chest pain and fever. The HRCT appearances of LCH vary according to the chronicity of the disease. In the early stages, nodules (which correspond with Langerhans cell granulomas) are the predominant features, while cysts tend to develop later. It has been shown that cysts in LCH probably arise because of focal dilatation of bronchi caused by destruction of small airway bronchial walls due to Langerhans cell lesions. This may initially result in the nodules appearing to cavitate and a differential diagnosis for cavitating nodules may sometimes be incorrectly entertained. - The combination of nodules, cavitating nodules and cysts in a smoker should allow a confident and accurate diagnosis to be made on CT alone. The cysts in LCH also have certain relatively unique features which allow a confident distinction to be made from LAM and emphysema. - Ttypically diffusely distributed, with a predominance in the lung apices and relative sparing of the lung bases - Sparing of the medial tips of the middle lobe and lingula - The cysts can have bizarre shapes and unequal sizes; at this stage the cysts probably reflect LC granuloma induced fibrosis rather than bronchial dilatation. Page 26 of 49

27 Fig. 11: Advanced langerhans cell histiocytosis with fibrotic changes. References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 27 of 49

28 Fig. 12: Advanced langerhans cell histiocytosis with fibrotic changes - another patient. References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Lymphangioleiomyomatosis (LAM) LAM is a rare multi-organ disease characterised by infiltration of immature-appearing smooth muscle cells in the airways and along lymphatics in the chest and abdomen. It occurs either as a pure pulmonary disease or in association with tuberous sclerosis and is characterized by pulmonary cysts. It is a disease that is almost exclusive to women of childbearing age and presents most commonly with dyspnoea or recurrent pneumothoraces and occasionally haemoptysis. Page 28 of 49

29 In some patients, together with the correct clinical picture, HRCT appearances may be regarded as pathognomonic. In other instances, where clinical or radiological features are not typical, open or transbronchial lung biopsy may be required. The typical HRCT pattern is one of diffusely distributed multiple lung cysts, although the number of cysts may vary. In patients with only a few cysts, it is possible that interspaced HRCT can be 'normal' and the diagnosis made only after biopsy for the investigation of recurrent pneumothorax for example. The precise aetiology of the cysts in not clear, but it may reflect focal bronchiolar dilatation caused by a ball-valve effect due to bronchial wall smooth muscle proliferation. There are some key signs that help in differentiating LAM from LCH. Perhaps the most useful differentiating sign is the distribution of cysts: - May involve the juxtaphrenic recesses - There is tendency to spare the extreme apices In contrast to LCH, the intervening lung parenchyma is usually normal, although superadded ground glass opacities have been reported. The cysts in LAM are typically thin walled and round in shape. Bizarre shaped cysts are less common in LAM than LCH and tend to be seen in more end-stage disease. Page 29 of 49

30 Fig. 13: Lymphangioleiomyomatosis - small left pneumothorax and right tube drainage. References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 30 of 49

31 Fig. 14: Lymphangioleiomyomatosis - same patient. References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 31 of 49

32 Fig. 15: Lymphangioleiomyomatosis - same patient - coronal reformatted CT image. References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT 2 - Scattered pulmonary cysts with ancillary CT signs Lymphocytic interstitial pneumonia (LIP) LIP is an uncommon benign lymphoproliferative disorder characterised pathologically by a diffuse lymphocytic infiltrate. It is often associated with collagen vascular Page 32 of 49

33 disorders, in particular Sjogren's syndrome, but is also seen in patients with HIV infection. th Non-infection associated LIP typically presents in women in the 5 decade, with shortness of breath or cough. The condition usually responds to treatment, but is known on rare occasions to be complicated by pulmonary fibrosis or to transform into lymphoma. Ground-glass opacities and nodules are almost universal features in LIP, with cysts seen in about two-thirds of patients. Interlobular septal thickening and reticular opacities have also been reported. The lung cysts are usually small (less than 3 cm), thin walled and distributed in a scattered, random distribution, though much larger cysts are also recognised. Page 33 of 49

34 Fig. 16: Lymphocytic interstitial pneumonia (blue arrow - cyst; orange arrow - nodule). References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Fig. 17: Lymphocytic interstitial pneumonia (arrow - nodule). References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 34 of 49

35 Fig. 18: Lymphocytic interstitial pneumonia (arrow - interstitial thickening). References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Ultimately, most patients with suspected LIP on clinicoradiological grounds will require lung biopsy to confirm the diagnosis and in some cases to exclude low-grade lymphoma. At the same time, clinico-radiological integration with histological findings is essential, because it can sometimes be difficult for the pathologist to distinguish LIP from hypersensitivity pneumonitis and NSIP. Sub-acute hypersensitivity pneumonitis (HP) HP is a diffuse granulomatous inflammatory disease of the lungs caused by exposure to a wide variety of agents ranging from organic particles to chemotherapy agents. Page 35 of 49

36 Patients often present with gradually worsening dyspnoea, but because the presence of a precipitating agent is not always obvious from the clinical history, radiology has a role to play in suggesting the diagnosis. The key histological findings are bronchocentric lymphocytic infiltration and poorly formed granulomas, but these abnormalities are not always identified on lung or transbronchial biopsy, adding sometimes to diagnostic uncertainty. Cysts on HRCT are seen in approximately 10% of patients with subacute HP and are usually few in number and random in distribution. Despite their low frequency, the presence of cysts can be a helpful clue in making a radiological diagnosis of HP, when identified in conjunction with the more classical signs of the disease: these are centrilobular ground glass nodules and a mosaic attenuation pattern. Furthermore, all of these signs of subacute HP can be seen in the more chronic fibrotic form of hypersensitivity pneumonitis. Contrasting imaging features and clinical history mean that differentiating between HP and PCP (Pneumocystis jirovecii) is never usually a diagnostic dilemma. PCP in patients with AIDS commonly presents with diffuse ground glass opacification, sepal thickening and occasional cysts, but with no small airways disease. Desquamative interstitial pneumonia (DIP) DIP is an uncommon disorder characterised by macrophage accumulation within the alveoli. It causes dyspnoea or cough and occurs almost exclusively in individuals exposed to cigarette smoke. Consequently, knowledge of the smoking history is mandatory before suggesting the diagnosis on radiological grounds. On HRCT, diffuse ground glass opacification is an expected finding in all patients. By itself, diffuse ground-glass opacification has a wide differential diagnosis, but the identification of small cysts admixed within the ground glass opacity is a unique feature to DIP, seen in about a third of patients. Page 36 of 49

37 Fig. 19: Desquamative interstitial pneumonia (blue arrow - microcyst; orange arrow ground glass opacification, lower lobes, peripheral). References: Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT 3 - Isolated or scattered cysts with no ancillary CT features When HRCT shows just a few scattered cysts with no other abnormal features, it can be difficult to determine whether there is a true underlying cystic lung disease or whether the cysts represent an incidental and unimportant finding. Certain aspects of the clinical history may point towards a diagnosis, but ultimately lung biopsy will be required if a particular condition is suspected. For example: In a female patient who presents with a pneumothorax, a few scattered cysts may signify an early form of LAM. Page 37 of 49

38 If a family history of recurrent pneumothoraces is elicited, a diagnosis of Birt-HoggDube syndrome may be suggested. This is a very rare condition that is associated with pneumothoraces, renal cell carcinomas and skin fibrofolliculomas. Reports suggest that there is a lower zone preponderance for cysts in Birt-Hogg-Dube. Another rare cause of lung cysts is malignancy. While cavitating malignant lung nodules are readily identified as such and do not normally pose diagnostic difficulties, very occasionally cystic metastases may present as exquisitely thin-walled cysts. Such a diagnosis should be considered if there is a history of primary squamous cell carcinoma, adenocarcinoma or sarcoma malignancies elsewhere, and in this scenario it is important not to dismiss new cystic opacities as an incidental finding. In the absence of suspicious clinical features, further investigation is unlikely to be instigated or necessary. Nevertheless, it is important to try and explain their presence, as a "simple" lung cyst are not a recognised normal phenomenon. Possible explanations include a focal area of centrilobular emphysema. Alternatively, a single cyst could be the residual manifestation of previous infection (i.e. a persistent pneumatocoele), as previously mentioned. In elderly patients, lung cysts have also been reported in asymptomatic non-smoking individuals, raising the possibility that they may represent part of the aging process. Page 38 of 49

39 Images for this section: Fig. 11: Advanced langerhans cell histiocytosis with fibrotic changes. Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 39 of 49

40 Fig. 12: Advanced langerhans cell histiocytosis with fibrotic changes - another patient. Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 40 of 49

41 Fig. 13: Lymphangioleiomyomatosis - small left pneumothorax and right tube drainage. Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 41 of 49

42 Fig. 14: Lymphangioleiomyomatosis - same patient. Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 42 of 49

43 Fig. 15: Lymphangioleiomyomatosis - same patient - coronal reformatted CT image. Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 43 of 49

44 Fig. 16: Lymphocytic interstitial pneumonia (blue arrow - cyst; orange arrow - nodule). Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 44 of 49

45 Fig. 17: Lymphocytic interstitial pneumonia (arrow - nodule). Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 45 of 49

46 Fig. 18: Lymphocytic interstitial pneumonia (arrow - interstitial thickening). Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 46 of 49

47 Fig. 19: Desquamative interstitial pneumonia (blue arrow - microcyst; orange arrow ground glass opacification, lower lobes, peripheral). Serviço de Imagiologia, Centro Hospitalar de Lisboa - Zona Central, Hospital de São José - Lavradio/PT Page 47 of 49

48 Conclusion The differential diagnosis for cyst lung disease may be organized on the basis of clinical history, serologic evaluation and the HRCT appearance of the cysts and ancillary HRCT findings. It is important for every radiologist to have experience in the differentiation between lung cysts and other pathology that may simulate those and to be familiarized with the appearances of thevarious cystic lung diseases, so as to allow an accurate differentiation and correct management of the patients. Page 48 of 49

49 References 1 - Beddy P, Babar J, Devaraj A. A practical approach to cystic lung disease on HRCT. Insights Imaging 2011;2: Ryu JH, SWENSEN SJ. Cystic and Cavitary Lung Diseases: Focal and Diffuse. Mayo Clin Proc. 2003;78: DM Seaman et al. Diffuse Cystic Lung Disease at High-Resolution CT. AJR 2011;196: Jain A, Anand K, Singla S, Kumar A. Congenital Cystic Lung Diseases. J Clin Imaging Sci 2013;3: Odev K, Guler I, Altinok T, Pekcan S, Batur A, Ozbiner H. Cystic and Cavitary Lung Lesions in Children: Radiologic Findings with Pathologic Correlation. J Clin Imaging Sci 2013;3:60. Page 49 of 49