Review Article

Imaging Findings of Focal and Multiple Cystic and Cavitary Lung Lesions

Kemal Ödev, Hüseyin Özbiner

Konya University, Meram Medical Faculty, Abstract Department of , Konya, Turkey Cystic and cavitary lung lesions constitute a spectrum of pulmonary Eur J Gen Med 2012;9 (Suppl 1):3-14 diseases diagnosed in both children and adults. Cysts and cavities are Received: 02.12.2011 commonly encountered abnormalies on chest radiography and chest computed tomography. High-resolution computed tomography (HRCT) Accepted: 17.01.2012 of the chest frequently helps define morphologic features that may serve as important clues regarding the nature of cystic and cavitary lesions of the lung. Occasionally, the underlying nature of the lesions can be readily apparent as in bullae associated with emphysema. Cystic and cavitary lung lesions can be diagnostic challange. Although many patients with cystic and cavitary lung lesions have a known un- derlying disease, in many cases the considerable overlap in morpho- logic features of these lesions tenders transthoracic needle biopsy necessary to establish the correct diagnosis. Key words: Radiography, CT scan, cyst, lung, cavitary

Fokal ve Multipl Kistik ve Kaviteli Akciğer Lezyonlarında Radyolojik Bulgular Özet: Kistik ve kaviteli akciğer lezyonları çocuklarda ve yetişkinlerde görülen akciğer hastalıklarının bir spektrumunu oluşturur. Kistler ve kaviteler akciğer radyografisinde ve bilgisayarlı toraks tomografisinde yaygın olarak görülen lezyonlardır. Yüksek çözünürlüklü bilgisayarlı tomografi (YÇBT) sıklıkla akciğerin kistik ve kaviteli lezyonları hakkında önemli ipuçları vererek morfolojik özelliklerini tanımlamaya yardım eder. Bazen, amfizem ile birlikte bül gibi, lezyonların altta yatan nedeni açıkça görülebilmektedir. Kistik ve kaviteli akciğer lezyonlarında tanısal zorluklar halen devam etmektedir. Kistik ve kaviteli akciğer lezyonları bulunan birçok olguda altta yatan bilinen bir sebep olmakla birlikte, birçoğunda bu lezyonların morfolojik özelliklerinde belirgin örtüşme olması nedeniyle doğru tanıyı koymak için transtorasik iğne Correspondence: Dr. Kemal Ödev Konya University, Meram Faculty of Medi- biyopisisi gerekmektedir. cine, Department of Radiology, Konya. Anahtar sözcükler: Radyografi, BT, kist, akciğer, kavite, Turkey E-mail: [email protected]

European Journal of General Imaging findings of cystic lung lesions

INTRODUCTION the lung) (1). remains the first imaging technique in the evaluation of cystic and cavitary lung The cysts and cavities are seen as foci of decreased lung lesions. However, computed tomography (CT) and high density with definable walls (1). In contrast, emphysema- resolution CT (HRCT) can show the size, shape and pre- tous airspaces usually lack such perceptible walls (bullae cise location of cysts and cavities when these lesions are and blebs are expection). The presence or absence of a not apparent on chest radiography. The purpose of this wall around a radiolucent area can be accurately depict- review is to describe the characteristic radiologic findings ed by high resolution computed tomography (HRCT), if it of focal and multiple lung cystic and cavitary lesions. is not apparent on chest radiography. The term cyst, cys- tic air space and cavity have overlapping meanings and Congenital abnormalities sometimes used interchangeably. The terms cyst and cav- Congenital lobar emphysema ity convey different meanings and ranges of diagnostic possibilities to clinicians (1). In the literature, the term Lobar emphysema can be either acquired, or secondary cyst is used to mean a clearly defined air-containing space or congenital. CLE refers to progressive overinflation of a surrounded by a relatively thin (≤4 mm) wall. In contrast, pulmonary lobe secondary to air trapping clinically, most the term cavity is used to refer to an air-containing le- infants with CLE present within the first 6 months of life, sions with a relatively thick (≥4 mm) wall or within an with symptoms and signs of respiratory distress. Bilateral area of a surrounding infiltrate or mass. Cystic lesions in or multifocal involvement is rare. With severe overdis- the lungs are rarely malignant. However, is tention of a lobe, contralateral lober compression results commonly the first diagnosis to consider for a cavitary and there is cardiomediastinal shift (Figure 1). CT scan lesion, particularly in a middle-aged or oder adult with a demonstrates which lobes or segments are involved. The history of cigarette smoking. Some cystic and cavitary le- affected lobe is overdistended and hypodense, with at- sions may be filled with fluid or solid contents. For exam- tenuated vascular markings (Figure 1) (1,2). ple, a bronchogenic cyst may be filled with fluid and -ap Bronchopulmonary dysplasia and Wilson-Mikity syn- pear as a mass lesion on chest radiography. The presence drome of an air-fluid level does not correlate well with benignity or malignancy (1). Solid contents within a cavity may be In the neonatal period, several disease entities, such seen in infectious processes (e.g. invasive ), as bronchopulmonary dysplasia and Wilson-Mikity and in necrotic tumors. The location of focal lesions may syndrome are associated with respiratory distress. be of help in narrowing the differental diagnosis (e.g. Bronchopulmonary dysplasia results infantile respiratory propensity of to affect the upper lobes of distress syndrome and respiratory with high oxy-

a b Figure 1. Congenital lobar emphysema. CT scan shows Figure 2. Type I congenital cystic adenomatoid malfor- a largehyperlusent area in the left hemithorax. There mation a.chest radiograph shows thin walled cysts with is marked overinflation in the left hemitoraks and the multiple internal septa expand left lung and displace mediastinal structures are shifted to the right side and diaphragm and b.CT scan shows replace- the lower lobe is compressed ment of the left lung by cystic lesions of varying sizes.

4 Eur J Gen Med 2012;9(Suppl 1):3-14 Ödev and Özbiner

Figure 3. Bronchogenic cyst a.Chest radiograph shows Figure 4. İntralobar sequestration in a child with recur- a bronchogenic cyst in theleft lung with an air filled rent pneumonia in the lower lobe. a.CT scan shows a level b.CT scan (lungwindow) shows a unilocular air- large multicystic mass b. The arterial supply to the filled bronchogenic cyst on the left lung sequastered segment (arrow) arises from the descend- ing aorta as demonstrated on the surface rendered 3-D image

gen concentrations. Multiple lung cysts reflect air trap- ity. CCAM is usually discovered in neonates, because of ping due to broncholitis or areas of destroyed lung sur- respiratory distress and may occasionally be discovered rounded by fibrous tissue. Lesions are typically bilateral. in older children or adults who have recurrent infec- Wilson-Mikity syndrome or pulmonary dysmaturity , has a tion (2-4). Stocker et al. (5) classified into three types radiologic appearance similar to that of bronchopulmo- based on clinical, gross and microscopic criteria. In type nary dysplasia, but is not associated with infantile respi- 1 CCAM, lesions consist of multipl large cysts (2-10 cm in ratory distress syndrome (3). diameter). Type 2 lesions have numerous smaller, more uniform-sized cysts (0.5-2 cm in diameter, rarely larger). Congenital cystic adenomatoid malformation of the Type 3 lesions are bulky solid lesions that usually involve lung an entire lobe or lung (2,4,6). Typical radiographic find- Congenital cystic adenomatoid malformation of the ing in patients with CCAM is a large air-filled multicys- lung (CCAM) is an uncommon developmental abnormal- tic lesion. However, variable radiographic features can

Figure 7. Centrilobular Figure 8. Panlobular Figure 6. The CT scan emphysema. The HRCT emphysema. The HRCT The HRCT shows Figure 5. shows bronchial wall thick- shows multiple areas of shows the panacinar em- bilaterally mucoid impac- ening and bronchiectasis low attenuation with mini- physema lesion that is tion and cystic bronchiecta- involving all of the lobes. mal or no perceptible walls seen in both lower lobes. sis in both lower lobes. Mucus plugs are seen with consistent with centrilobu- in several of the dilated lar emphysema and finding bronchi (Cystic fibrosis) pulmoner fibrosis

Eur J Gen Med 2012;9(Suppl 1):3-14 5 Imaging findings of cystic lung lesions

Figure 9. Distal acinar em- Figure 10. Bullous emphy- Figure 11. The HRCT Figure 12. The honeycomb- physema. TheHRCT shows sema. The CT scan shows shows a large bullae on ing in idiopathic pulmonary distal acinar and central a large bullae in the left the right and presence of fibrosis. The HRCT shows acinar emphysema in both lung and absence of em- of distal acinar emphy- honeycomb cysts with a dis- lungs. physema in the lung. sema in both lungs. tinct predominance in the- peripheral and subpleural regions.

make diagnosis difficult (Figure 2). CT demonstrates the optimal demonstration of cyst location, morphology and air-filled or fluid-filled cystic lesions with thin walls and contents (Figure 3) (7,8). air-fluid levelsin cysts or a combination of these findings (Figure 2). Classically, two forms of pulmonary sequestration (PS) Bronchogenic cysts have been described: intralober (ILPS) and extralober Bronchogenic cysts are found most frequently in the me- (ELPS). ILPS is a segment of pulmonary tissue that shares diastinum or lungs, but they can develop in extrathoracic the visceral pleural covering of normal adjacent lung tis- locations, such as neck, pericardium or abdominal cavity sue and are usually located in the posterobasal portion of (2,4). On chest radiography, an intrapulmonary broncho- the lower lobes. The arterial supply is typically from tho- genic cyst may appear as well-defined, noncalcified lung racic or upper abdominal aorta and most drain by way of mass with water density or air-space cysts with air-fluid the pulmonary venous system to the left atrium. ELPS is levels (Figure 3). CT often demonstrates a cyst not visible entirely seperate segment of pulmonary tissue that is in- by conventional radiographic techniques. CT density of vested in its own pleural layers. ELPS may also be located bronchogenic cysts can vary from typical water density in the mediastinum, pericardium and within or below the (0 to 20 HU) to high density (89 to 99 HU). CT provides hemidiaphragm (2,9). The abdominal or thoracic aorta

a b Figure 14. Staphylococcal pneumonia. The CT scan Figure 13. Wegener granulamatosis. a;The CT shows a shows multiple cavitation in the right and left lobes large cavitating mass associated with consolidation in the right upper lobe. b; Cavitating nodules in the left subpleural region.

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a b Figure 16. Pulmonary abscess. The CT scan shows con- Figure 15. Pneumatocele formation in staphylococcal solidation with cavitation and air- fluid level in the pneumonia a-b .The CT scan show multiple pneumoto- right lobe and cavitating lesion on the left. celes with thin walled in right lower lobe pneumonia.

usually supplies the arterial vessels. In 80 % of cases, ve- variable solid, fluid, hemorrhagic and mucus-containing nous drainage is to the systemic circulation , usually by components (9). way of azygous system or IVC. It is difficult to distinguish Airway abnormalities between an ILPS and ELPSs on plain raidograph alone. CT or MRI provide a more gobal assessment of sequestration Bronchiectasis and are in general, recommended for full evaluation. CT Bronchiectasis is a disease process characterized by ab- images shows an ILPS as a more irregular outline and also normally dilated bronchi with thickened bronchial walls, a heterogenous appearance. Cysts and cavities with air- and which has a number of potential underlying causes. filled levels may be seen (Figure 4). CT images show an Ninety percent of bronchiectatic patients have some ab- ELPS as a homogenous, well-circumscribed areas of soft normalities on chest radiograph as follows: focal opacifi- tissue attenuation (2). With its multiplanar capability, MR cations, scattered irregular opacities, linear or plate-like imaging can successfully demonstrate the systemic feed- atelectasis or dilated and thickened airways that appear ing vessels of an intralober sequestration (Figure 4). MR as ring-like shadows (10) (Figure 5). HRCT has now be- imaging can also depict the pulmonary venous return of come the best tool for diagnosis. Typical findings on chest the lesion and the relationship of the draining vein to the CT scan tend to correlate with type of bronchiectasis cardiac chambers. MR imaging can also reveal the cystic present (e.g. cylindrical, saccular or varicose), although nature of many intralober sequestrations, as well as the

a b Figure 17. Active cavitary pulmonary tuberculosis.a. Figure 18. Cystic pneumocystis carinii pneumonia.The The HRCT shows an irregular small and large thick- HRCT shows poorly marginated air-space nodules and walled cavity in the left upper lobe.b. CT scan obtained foci of graund glass opasification scattered through out at level of carina shows thicked walled cavities associ- the upper lobes and small thin-walled cavities. ated with segmental consolidation and scattered nod- ules and clusters of nodules that are typical of endo- broncial spread of infection (three-in-bud appearence)

Eur J Gen Med 2012;9(Suppl 1):3-14 7 Imaging findings of cystic lung lesions

b a b a Figure 19. Pulmonary (mycetoma) a. Figure 20. İnvasive pulmonary aspergillosis with acute Chest radiograph shows pulmonary cavity in the right .a.active early lesion of invasive pulmonary upper lung surrounded by circumferential pleural thick- aspergillosis with CT halo sign.b. Four months later, le- ening and containing aspergilloma.b. CT scan shows a sion are healed. CT shows residual thin-walled cyst. right intracavitary aspergilloma with associated pleural thickening.

patterns may be mixed. HRCT findings of bronchiectasis severe in the upper lobes. The bronchiectasis is most of- include increased bronchoarterial ratio, lack of appropri- ten cylindrical, but varicose and cystic bronchiectasis can ate airway tapering, bronchial wall thickening and irregu- be seen in advanced cases (12). larity, mucoid impaction and mosaic perfusion with air Emphysema trapping (Figure 5). Bronchial dilatation is considered to be present when the bronchus is larger than the adjacent Emphysema is defined as a condition of the lung character- pulmonary artery (signet ring sign) or when bronchi are ised by permanent, abnormal enlargement of the airspac- visible within 1 cm of the pleura (10-12). es distal to the terminatal bronchiole, accompanied by destruction of the airspace walls (11,13). The HRCT find- Cystic fibrosis ings of emphysema include centrilobular(centriacinar), Cystic fibrosis is transmitted as an autosomal recessive panlobular(panacinar) and distal acinar (paraseptal). trait. The CT findings of cystic fibrosis include bronchial Centrilobular emphysema (Figure 7) is found most com- wall thickening, bronchiectasis and mucus plugs within monly in the upper lobes and manifests as multiple small the bronchi (Figure 6). The abnormalities are usually most areas of low attenuation without a perceptible wall,

a b Figure 21. Allergic bronchopulmonary aspergillosis in Figure 22. Hydatid cyst. CT scan shows a hypoatenuat- a 50- year -old asthmatic patient a.The HRCT shows ing crescent sign (meniscus sign) fungus ball with in multiple dilated bronchi in the left upper lobe and b. lower lobe.

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Figure 23. Hydatid cyst. Chest radiograph and CT scan Figure 24. Hydatid cyst. Chest radiograph shows a shows the water lily sign created by collapsed and large homogenous solid mass in the right lower lung. crumpled endocysts floating freely in the most depen- CT scan shows an “empty cyst” after complete evacua- dent part of the cyst. tion parasitic membranes (1 year after).

producing a punched-out appearance. In contrast to ple lung cysts. Bullae can occur in otherwise normal lung centrilobular emphysema, panlobular emphysema is his- (Figure 10), but are often associated with emphysema topathollogically characterized by complete destruction (Figure 11). Pathologically, bullae are filled spaces lined of the entire pulmonary lobule. On HRCT panlobular em- by pleura, connective tissue septa or emphysematous physema appears as extensive low attenuation that mani- lung. The walls of bullae appear hair-thin (Figure 11). CT fests as diffuse simplification of pulmonary architecture scan may be necessary to demonstrate the walls and es- (Figure 8) and the pulmonary vessels appear stretched tablish the presence of bullae (13). and attenuated in the presence of panlobular emphysema Pulmonary fibrosis and honeycomb lung (11,13). Distal acinar or paraseptal emphysema appears on HRCT imaging as multiple areas of low attenuation In patients with chronic interstitial fibrosis, fibrosis - as with thin, definable, uniform walls distributed in the sub- sociated with areas of lung destruction and disorganisa- plevral regions of lung (Figure 9). tion of lung architecture (honeycomb) results in a cystic appearance on HRCT scans. That can be characterized Bullous emphysema and localized precisely (Figure 12). Honeycombing results Bullosu emphysema is the most common cause of multi- in cystic spaces several milimeters to several centime-

Figure 27. Cavitating Figure 26. Cavitating me- Figure 25. Squamous cell associated tastasis associated with carcinoma of bronchus with pneumothorax testis carcinoma. The CT showing cavitation. The CT from osteogenic sarco- scan shows multiple met- scan shows that cavity wall ma. The CT scan shows astatic nodules in both is of variable thickness and a thick walled cavity in lungs and there are several the presence of mural the right lung and pneu- cavitating nodules. nodule mothorax in the left

Eur J Gen Med 2012;9(Suppl 1):3-14 9 Imaging findings of cystic lung lesions

a b Figure 29. Septic pulmonary emboli in 30 years old Figure 28. Acute with infarction who had bacterial endocarditis. The CT scan shows scat- a.Coronal reformation obtained along the main axis of tered mostly peripheral poorly defined foci of air-space the left pulmonary artery shows the presence of en- consolidation and multiple round pulmonary cavities doluminal clots within the left pulmonary artery b. with thin walls. Note that a number of these cavities Coronal reformat CT reveals the cavitating infarct and appear to be associated with feeding vessels. residual scarring of pleura in the left lung and mosaic perfusion in both lungs.

ters in diameter, which are often peripheral in location areas of attenuation, linear areas of attenuation, alveo- and are characterized by thick clearly definable walls. lar or pseudoalveolar consolidations, irregular interfaces, Honeycombing often is associated with other findings of peribronchovascular thickening, lung distortion, honey- fibrosis, such as septal thickening, intralobular lines and comb cysts, cavitary nodules and traction bronchiectasis irregular pleural thickening (14). Traction bronchiectasis; (15). CT provides a precise assessment of the pattern and In patients who have severe lung fibrosis and distortion of distribution of the disease and it depicts cavitary lesions lung architecture, so-called traction bronchiectasis may not shown with chest radiography (4,15). be present. In the presence of severe fibrosis and par- Wegener’s granulomatosis ticularly honeycombing, traction by fibrous tissue on the bronchial walls can result in areas of irregular bronchial Wegener’s granulomatosis (WG) is an idiopathic disease dilatation (e.g. bronchiectasis) (14). characterized by a granulomatous and necrotizing vascu- litis (16). The CT lesions of pulmonary WG include nod- Granulomatous diseases ules, masses, pulmonary consolidations and ground glass opacities. Nodules are the most frequent parenchymal abnormality. In untreated disease, nodules tend to in- The CT lesions of pulmonary sarcoidosis include nodular

Figure 30. Langerhans cell Figure 31. Lymphangi- histiocytosis. The CT scan oleimyomatosis in a 40- year- shows diffuse thick walled old woman. The HRCT shows Figure 32. Traumatic pseudocyst. The CT scan shows cavitary nodules and small numerous discrete round, cystic lesions with an air-filled level and some- sur nodular opacities. thin walled lung cysts. rounding lung contusion in the left lower lobe.

10 Eur J Gen Med 2012;9(Suppl 1):3-14 Ödev and Özbiner crease both in size and number and may cavitate (Figure Pneumocystis carinii pneumonia 13). The cavitary nodules may occasionally become in- Pneumocystis carinii is the commonest cause of pneumo- fected to give an air-filled level (4,16). nia in patients with AIDS, occuring in 60 % to 80 % pa- Infections diseases tients. Radiographic and CT manifestations of P.carinii pneumonia is bilateral, central or basal, reticular or Infectious diseases due to bacteria, fungi or parasites ground glass opacification, which may progress over a few can result in cystic lesions in the lung. Staphylococcus days to diffuse air-space consolidation. Cavitation is rare aureus, Klebsiella and anaerobic bacteria commonly re- and has been reported in 10 % of cases. Thin-walled, air- sult in the development of thick or thin-walled, air-filled filled lung cysts occur frequently (38 % of cases) (Figure cystic lesions (Figure 14). Pneumatocele are thin-walled, 18). They often persist after treatment. Such cavities cystic lesions commonly seen in children (Figure 15) and which are often apical and subpleural may cause pneuo- infrequently in adults as a sequelea of Staphylococcal mothorax (19 ). pneumonia (1,4). Gram-negative, anaerobic bacteria and occasionally pneumonia are responsible Fungal infections for the development of lung abscesses. A is In the liteature, several forms of pulmonary aspergillosis a thick-walled cavity that contains purulent material re- have been described, including saprophytic (aspergillo- sulting from a pulmonary infection. It is believed to be ma), invasive, semi-invasive and allergic bronchopulmo- less common in children than adults. Secondary lung ab- nary aspergillosis (ABPA) (4,20). The radiographic presen- scesses may be seen in children at increased risk of pul- tations of pulmonary aspergillosis vary depending on the monary aspiration, immunocompromised hosts and those form of the disease and the patient’s clinical setting. At with underlying localized structural lung abnormalities or CT aspergillomas are characterized by the presence of a generalized suppurative lung disease (17). The character- solid, round or oval mass with soft tissue opacity within istic appearance of a lung abscess on a CT image is thick- a lung cavity. The mass is typicially seperated from the walled cavity. It contains mobile, central fluid occuring in cavity wall by an air-space (“air cresent sign”) and is of- the middle of an area of consolidated lung. An air-filled ten associated with thickening of the wall and adjacent level is often appearent on the CT, even when it is not pleura (Figure 19) Characteristic CT findings in invasive evident on the chest radiograph (Figure 16). aspergillosis consist of nodules surrounded by a halo of Mycobacterial infection groung glass attenuation (“halo sign”) or pleura-based, wedge-shaped areas of consolidation (Figure 20). CT find- Two forms of pulmonary tuberculosis (Tb) is known: ings in allergic bronchopulmonary aspergillosis (ABPA) Primary and post-primary or reactivated tuberculosis consist primarly of mucoid impaction and bronchiectasis which is more frequent in the adult population. The high involving predominantly the segmental and subsegmen- resolution CT findings of active post primary Tb are cen- tal bronchi of the upper lobes (Figure 21). Semi-invasive trilobular lesions appearing as a nodule or a branching (chronic necrotizing) aspergillosis may be seen at CT as linear structure (tree-in-bud appearance), bronchial wall an endobronchial mass, obstructive pneumonitis or col- thickening, a poorly defined nodule, a cavity and lobular lapse or hilar mass. Only a few reports have described CT consolidation (18). Cavities result when areas of caesa- findings in aspergillus necrotising bronchitis involving the tion erode into the bronchial tree, expelling liq- central airways (20). uefied debris. CT is more sensitive than plain radiograph in the detection of small cavities, particularly ones in the Hydatid disease apices, lung bases and paramediastinal and retrocardiac The localization of hydatid cysts in humans is mostly he- locations. On CT scans, cavities due to mycobacterial dis- patic (55 to 75 percent), with the lungs being the sec- ease can be thick or thin walled and smooth or irregular ond most frequent location in adults (10 to 30 percent). with or without air-filled levels (Figure 17) (18). Those Radiographically, the cysts are commonly seen as spheri- caused by atypical mycobacteria are indistinguishable cal, homogenous masses with smooth borders surrounded from thosed by caused by M.tuberculosis. Tuberculosis by normal lung tissue. An intact cysts is filled with clear may manifest with different patterns and distribution fluid (21). Cysts may rupture spontaneously (Figure 22) or in patients with diabetes or acquired due to trauma. As the cysts enlarges and erodes into the syndrome (AIDS) (4).

Eur J Gen Med 2012;9(Suppl 1):3-14 11 Imaging findings of cystic lung lesions bronchioles, air enters the potential space between peri- Miscelleaneous diseases cyst and endocyst and appears as a thin lucent crescent Bronchiolitis obliterans organising pneumonia (crescent or meniscus sign) (Figure 22). When hydatid cyst completely collapsed, the crumpled endocyst floats Bronchiolitis obliterans organising pneumonia (BOOP) is freely in the cyst fluid (water lily sign) (4) (Figure 23). an unusual condition that is characterized pathologically Complicated hydatid cysts, either ruptured or infected, by the presence of polipoid granulation tissue in the lu- are also difficult to differentiate from other cavitary le- men of bronchioles and alveolar ducts. It is usually associ- sions, such as active cavitary tuberculosis (21). In cases of ated interstitial and airspace infiltration by mononuclear completely empty cysts (Figure 24), a variety of diseases cells and foamy macrophages (25). The most radiological that produces or mimic air-containing cavities should be appearance is that of bilateral, multifocal, non-segmen- considered in the differential diagnosis (21). tal and pathcy areas of consolidation. Both cavitation and are rare manifestations of BOOP. Focal Malignant neoplasms solitary nodule or mass, which may simulate a bronchial Lung cancer carcinoma, and multiple nodules or masses which may also be associated with cavitation (25). Cavitation in bronchogenic carcinoma is common and oc- curs in about 10 % to 15 % of cases. Eighty percent of Embolic diseases cavitating lung tumors are squamous cell carcinomas, Pulmonary embolism with infarction whereas the remaining 20 % are adeno and large cell car- cinomas. Bronchoalveolar carcinoma may occasionally This is an uncommon cause of cavitary lung nodules. present as multiple cavitary nodules (1,4,22). Typically, Pulmonary embolism causes infarction in less than 15 % the cavity will have thick walls, nodular extensions of tu- of cases, and cavitation is found in only about 5 % of in- mor (mural nodules) projecting into the lumen of cavity farctions. Cavitary pulmonary infarction has also been re- are frequent (Figure 25). Occasionally, a cavitated lung ported in immunocomprimised patients (1). The cavities cancer will have smooth, thin walls. Rarely, a meniscus or most frequently have well-defined borders, round or oval air-crescent sign may be seen in association with a cavi- shape and a wall thickness ranging from 1 to 2 mm which tated bronchogenic carcinoma (23). decreases overtime (Figure 28) (1).

Metastatic disease Septic pulmonary emboli

Cavitating lung metastases can occur in any primary Septic pulmonary emboli occur in patients with con- malignancy. However, previous studies have shown that genital heart diseases, endocarditis (often due to in- they are more commonly associated with primary squa- travenous drug abuse), infected in dwelling catheters. mous cell carcinoma. Cavitating lung metastases have Radiographically, the lesions appear as multiple, scat- been reported with primary lung, head and neck, thy- tered consolidation. The pattern may change rapidly and roid, breast, bone, kidney, pancreas, colon and rectum, new lesions appear as other resolve. Thin walled cavi- urinary bladder, penis, testis (Figure 26), uterine, cervix ties can develop (Figure 29). Fluid levels are infrequently and skin carcinomas (4,24). The aetiology of the forma- seen (3). tion of a cavity is not clear. Metastatic sarcomas can Collagen vascular diseases also cavitate and a pneumothorax can be complicated (Figure 27). is known to induce cavitation. Lung involvement in (RA) may mani- Pneumothorax occurs most frequently with an osteosar- fest with necrobiotic nodules, pleural effusions and/or comatous tumors. Necrosis of subpleural metastases is pleuritis. Rheumatoid (necrobiotic) nodules are found in thought to produce a bronchopleural fistula that results up to 20 % of patients. Nodules typically range from a mi- in a pneumothorax. The frequency of a pneumothorax in limeter to centimeters in size. Nodules identified in HRCT a patient with an osteosarcoma has been reported to be must be distinguished from malignant and infectious le- approximately 5 % - 7 %. A spontaneous pneumothorax in sions. Caplan’s syndrome refers to conglomeratious of a patient with a sarcoma should raise the possibility of nodules seen in patients with the combination of RA and occult pulmonary metastases. In such cases, CT may help pneumoconiosis (26). detect occult pulmonary metastatic nodules (24).

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