I. Solitary intrapulmonary cavity
(A) Lesions with single cavity in the lung
1. Peripheral type bronchopulmonary carcinoma: the incidence of cavitation in peripheral type lung cancer is 2%-16%, among which: squamous cell carcinoma accounts for 80%, adenocarcinoma and large cell carcinoma accounts for 20%, bronchoalveolar carcinoma can occur as cavitation or thin-walled cystic lesion, solitary or multiple. Small cell undifferentiated carcinoma generally does not occur in cavities.
2, pulmonary tuberculosis: cavitation accounts for about 40% of pulmonary tuberculosis in adults. It is mainly seen in secondary tuberculosis, and a few primary lesions may also form cavities. Cavities may be thick-walled or thin-walled.
Cavities in pulmonary tuberculosis are classified as:
(1) cavities of infiltrative caseous foci: cavities resulting from caseous necrosis within infiltrative lesions. The wall of the cavity is thin and consists mainly of proliferating tuberculous granulation tissue, and the inner wall is a thin caseous material.
(2) Fibrous cheese cavity and cheese cavity: cavities occurring in lesions with thicker cheese layer and thinner tuberculous granulation tissue and fibrous envelope in the cavity wall. The fibrous envelope of the tuberculous bulb is intact.
(3) Fibrous cavity: with a typical 3-layer structure of caseous necrosis, tuberculous granulation tissue, and fibrous tissue. Fibrous tissue is the main component of the cavity wall. Due to the contraction and pulling of fibrous tissue, the cavity morphology is irregular.
3.Lung abscess: the wall of acute lung abscess is mainly inflammatory exudative lesion, and the wall of chronic lung abscess is mainly composed of fibrous tissue. Lung abscess occurs after pneumonia, inhalation and lesions spread from outside the lung, the latter seen in amebic lung abscess.
4, pulmonary mycosis: mainly seen in new cryptococci, A-shaped bacteria, etc.
5, pneumoconiosis cavities: cavities occur on the basis of progressive pneumoconiosis fusion blocks, often combined with pulmonary tuberculosis. The cavity lesion is large, irregular in shape, and the cavity wall is predominantly thick-walled with uneven thickness. The inner wall is a thinner layer of dry for tuberculosis ball or cheese wall, thin wall or uneven thickness.
6, other diseases: such as pulmonary infarction and nodular disease.
(B) Differential diagnosis of single cavity in the lung
The differential diagnosis of solitary cavity is based on the size of the cavity lesion, the thickness of the cavity wall, the performance of the inner and outer edges of the cavity, and the abnormal morphology in and around the cavity.
The size of the cavitated lesion: cavitations occurring in nodules below 2 cm are more common in tuberculosis, and less common in lung cancer below 2 cm. cavitations occurring in masses above 4 cm are more common in lung cancer. Some tuberculosis cavities such as fibrous thick-walled cavities and fibrous cheese cavities are also larger, the former with irregular morphology, and some of the latter are difficult to distinguish from lung cancer and need to be combined with clinical and laboratory tests. Chronic lung abscess cavities can be larger or smaller. Coal workers’ pneumoconiosis cavity lesions are larger.
2, the thickness of the cavity wall: the cavity wall is generally thicker than 3mm called thick-walled cavity, <3mm thin-walled cavity. Thick-walled cavities are more common in diseases such as lung cancer, fibrous caseous cavities of pulmonary tuberculosis, caseous cavities and fibrous thick-walled cavities, and acute and chronic lung abscesses. Thin-walled cavities are seen in infiltrating caseous focal cavities and fibrous thin-walled cavities of pulmonary tuberculosis. Uneven wall thicknesses are seen in lung cancer and tuberculosis, with significant thickness heterogeneity making the cavity eccentric or of a specific shape. The walls of lung cancer cavities are generally thicker on the hilar side of the lung, and the cavities are more lateralized. The tuberculosis bulb is the first to soften in the caseous lesion at the opening of the draining bronchus, so the cavity cavity begins to be located on the hilar side of the lesion, i.e., where it connects to the draining bronchus, in a small round shape. The cavity further develops into a crescent shape, also mostly located on the hilar side of the lesion, and finally can form a round-like cavity. The cavity caused by mycobacteria can be thick-walled, thin-walled or unevenly thick and thin according to the type of pathogenic bacteria.
3, the inner edge of the cavity: the inner edge is smooth in lung abscess and tuberculosis fiber cavity; the inner edge is rough in lung abscess and tuberculosis fiber cheese cavity; the inner edge of the cavity is uneven in lung cancer and tuberculosis fiber cheese cavity; the wall nodules of the inner edge of the cavity mainly occur in lung cancer, and the unliquefied cheese material in tuberculosis fiber cheese cavity can also form wall nodules.
4.The outer edge of the cavity: clear outer edge of the cavity is seen in tuberculosis fibrous cheese cavity, chronic lung abscess, and some lung cancer cavities also have smooth and clear outer edge. The outer edge of the cavity has burr and “
The outer edge of the cavity with burr and “radiographic crown” image is seen in fibrous thick-walled cavity of pulmonary tuberculosis and lung cancer. Those with lobes on the outer edge are mostly seen in lung cancer.
5.Peripheral cavity: satellite foci are seen in various cavities of pulmonary tuberculosis. Linear images between the lesion and the pleura can be seen in lung cancer, tuberculosis and lung abscess cavities. The lamellar infiltrative images around the cavity are acute lung abscess, infiltrative caseous focal cavity, and some limited lamellar images are seen near chronic lung abscess. Those with obvious emphysema and fibrous cord shadow around the cavity are mostly seen in pneumoconiosis.
6, cavity cavity contents: air-fluid planes are mainly seen in acute lung abscesses. It is generally believed that there is no gas-fluid plane in tuberculosis cavity, but some studies point out that gas-fluid plane accounts for 9% to 21% in tuberculosis cavity, which is mostly combined with infection and bleeding. The solid components in the cavity are tumor nodules, caseous necrotic material, clots and mycobacterial balls, etc., which make the cavity behave in different forms against the gas in the cavity. Mycobacterial balls occur in lung cancer, tuberculosis and chronic lung abscess cavities, or within bronchiectasis and pulmonary cysts, as round-like movable nodules, mostly located at the site of fallout. Crescentic cavities are bow-shaped gas shadows, always located above the mycoblobule. If the cavity contents are attached to the cavity wall, such as invasive A-shaped mycosis, lung cancer, tuberculosis cavity, the crescent-shaped gas shadow may be located lateral or inferior to the cavity. If the cavity contents are attached to the anterior or posterior wall of the cavity, the posterior-anterior projection forms a “
target-like sign”. Some solid contents are located above the liquid to form the “water floating sign”, which is seen after the endothelial rupture of fine grain echinococcosis cyst.
7.Enhancement performance: generally used for the differential diagnosis of thick-walled cavernous lesions of 2 cm to 3 cm in size. The cavity wall of fibrous cheese cavity of pulmonary tuberculosis does not strengthen or has thin peripheral reinforcement, while the wall of lung cancer cavity is largely strengthened.
II. Multiple cavities in the lung
(A) Lesions of multiple cavities in the lung
1, pulmonary tuberculosis: any tuberculosis cavity can be multiple, mostly bronchially disseminated tuberculosis cavities.
2.Pulmonary metastases: about 4% of pulmonary metastatic nodules have cavities in them, and squamous epithelial carcinoma is the most common, accounting for 69% of pulmonary metastatic cavities in X-ray examination . However, according to CT examination, 9.5% of adenocarcinoma metastases have cavities and 10% of squamous carcinoma metastases have cavities.
However, according to CT examination, adenocarcinoma metastases with cavities accounted for 9.5% and squamous carcinoma for 10%. The common primary malignant tumors that can develop cavitary lung metastases are: squamous epithelial carcinoma of the head and neck, adenocarcinoma of the gastrointestinal tract and breast cancer. The cavity walls are irregularly thick to very thin and smooth. The thin-walled metastatic cavities are mostly caused by primary sarcomas and adenocarcinomas.
3.Hematogenous multiple lung abscesses: caused by Staphylococcus aureus sepsis.
4, mycobacteria: mainly seen in cryptococcosis and invasive A-shaped mycosis.
5, other diseases: pneumoconiosis, parasitic diseases (mainly seen in pulmonary schistosomiasis), collagen-vascular disease rheumatoid nodules), sarcoidosis (
Weil’s granuloma, nodular disease and eosinophilic granuloma), vascular diseases (septic emboli, mostly caused by trauma or vascular built-in retention catheters, causing multiple small vessel embolism and septic inflammation and cavitation), malignant lymphoma and histiocytosis, etc.
(B) Differential diagnosis of multiple cavities
The differential diagnosis of multiple cavities in the lungs should be combined with the distribution characteristics of the cavities, the location, the combined images and dynamic changes in the lungs, etc.
1, multiple smaller cavities in both lungs: cavity lesions are mostly below 2 cm. It is mainly seen in pulmonary tuberculosis, lung metastases and lung abscess. Less common diseases are eosinophilic granuloma, septic pulmonary embolism or pulmonary infarction. The differential diagnosis is based on the morphology of the cavity and the combined lesions in the lungs.
(1) Pulmonary tuberculosis: cavities are of uneven size and can be thin-walled or thick-walled. In the differential diagnosis, it should be noted that each cavity generally has the characteristics of a solitary tuberculous cavity. If the cavity is lateralized to the hilar side of the lung, there is a draining bronchus, surrounded by satellite foci, combined with speckled and corrugated images elsewhere in the lung, and the lesion is unevenly dense and may have foci of calcification. The lesions are more frequent in the posterior segment of the two lung apices and the dorsal segment of the lower lobe.
(2) Metastases: Multiple cavities in the lungs are often combined with multiple nodules. The overall distribution of cavities and nodules has the characteristics of randomly distributed nodules, i.e., located in the subpleural, peri-bronchial vascular bundles and lung parenchyma, with approximately the same distribution in each site. The size of the lesions varies, and the density of the lesions is more uniform.
(3) Multiple pulmonary abscesses: cavities are uniform or uneven in size, cavity walls are more thick, fluid levels may be present in the cavity, and multiple patches and faint nodular lesions are more common in the lung.
(4) Eosinophilic granuloma: granulomatous lesions dominated by eosinophils around the fine bronchi, forming multiple small nodules and cavities within the nodules, with lesions distributed in the center of the lobules and more common in the upper lobes.
2. Multiple large cavities scattered in both lungs: tuberculosis is the most common.
(1) Tuberculosis: can be cavities with infiltrative cheese foci, fibromatous cavities and fibrous thick-walled cavities surrounded by speckles, nodules and cords images, mostly located in the posterior segment of the upper lobe apices and the dorsal segment of the lower lobe.
(2) Mycobacteria: Cryptococcus neoformans is more common, with blurred outer edges of cavities, combined with lamellar and blurred nodular images, and rapid dynamic changes.
(3) Pulmonary schistosomiasis: generally thin-walled, single- or multi-housed, and may be surrounded by striae and patchy images.
(4) Wechsler’s granulomatosis: the lesion is a multiple nodule in the lung, consisting of granuloma and inflammation. Cavitation occurs within the larger nodules, mostly occurring in lesions of 2 cm or more.
(5) Lymphoma: Cavitation occurs in nodular and mass-type lymphomas. The lesions are multiple, vary in size, and are thin-walled or thick-walled cavities.
(6) Vascular septic emboli: multiple cavities combined with multiple nodules and wedge-shaped images. Some cavities can be smaller, and the cavities are seen to be connected to the blood supply vessels.
Third, the cavity of lung lobes and lung segment lesions
Lobar and segmental lesions or atelectasis can be combined with cavitation, mainly lobar pneumonia, lung abscess, tuberculosis and lung cancer.
(A) Pneumonia
1, acute pneumonia combined with lung abscess: some lobar pneumonia can be combined with acute lung abscess. x-ray and CT show translucent shadows and air-fluid planes within the lobe or lung segment solid images. The cavity is usually large and the main pathogenic organism is S. pneumoniae. Other diseases that cause similar images are lung abscesses complicated by certain gram-negative bacilli, such as Klebsiella, and are mostly seen in immune-compromised patients.
2, lung abscess combined with chronic pneumonia: chronic pneumonia may present as a solid shadow of a lobe or segment of the lung, which may be combined with a reduction in lung volume. It is usually a single cavity and can be combined with bronchial dilatation.
(II) pulmonary tuberculosis
1, worm-eaten cavities: also known as wall-less cavities, seen in case of caseous pneumonia and large foci of fibrous cheese. It is usually a single cavity and can be combined with bronchial aka wall-less cavity, cheese cavity, seen in case of caseous pneumonia and large foci of fibrous cheese. The image shows a lobe, lung segment or a large solid shadow in a single, multiple or fused form, with a cavity diameter of about 0.5-1.0 cm, round-like, and faint cavity wall.
2.Sclerotic multifocal cavity: the cavities in the lung destroyed by pulmonary tuberculosis are multiple, round or irregular, often closely connected, with a large amount of fibrous connective tissue in the cavity wall, surrounded by a variety of forms and different densities of tuberculosis foci, such as cheese tissue, granulation tissue, pulmonary sclerosis, pleural thickening, etc.
3, chronic fibrous cavity type tuberculosis: the cavity is a fibrous thick-walled cavity, often multiple. Surrounded by infiltration, cheese nodules, fibrosis and pleural thickening and other lesions, the volume of the lung is reduced.
4.Lung abscess combined with obstructive bronchial disease: central lung cancer or obstructive pneumonia and pulmonary atelectasis caused by other tumors or lesions of the bronchus can be combined with lung abscess. CT enhancement scan or MRI can show necrotic and liquefied lesions in obstructive pneumonia.
IV. Cavity-like lesions
Cavernous lesions in the lungs need to be differentiated from cavities. A cavity is an abnormal expansion of a physiological cavity in the lung. Common lesions include pulmonary cysts and alveoli. On imaging, the wall thickness of a cavity is 1 cm or less, which is the main basis for differentiating it from a cavity. In the differentiation of cavities, isolated cavities are usually pulmonary cysts, while cavities with emphysema are mostly alveoli. Pulmonary cysts are a combined manifestation of Staphylococcus aureus pneumonia. In some cases cavities resemble cavitational lesions and should be further differentiated.