Comments and Illustrations of the European Federation of Societies for Ultrasound in Medicine Guidelines: Benign Pleura Lesions (Benign Pleura Thickening, Lesions and Masses)-What Can Be Seen on Transthoracic Ultrasound?

Abstract

Pleural thickening can be the result of inflammation or infection but can also have a neoplastic origin. Depending on the clinical context, a pleural lesion or mass is often initially suspected of malignancy. Benign pleural tumors are rare, and their appearance on ultrasound (US) is also described less frequently than pleural metastases or malignancies. There are few descriptions of contrast-enhanced Ultrasound (CEUS) in particular. This review introduces the basics of transthoracic ultrasound (TUS) of the pleura and CEUS of the pleura and lung. CEUS is recommended for pulmonary applications in the EFSUMB guidelines in non-hepatic applications. This article provides an overview of the characteristics of benign pleural thickening, tumor-like lesions, and benign pleural tumors on transthoracic B-mode US with color Doppler imaging (CDI) and CEUS. In detail, characteristics in TUS and CEUS are described for infectious/inflammatory pleural thickening (empyema, tuberculous pleuritis, hemothorax, fibrothorax), pleural thickening in various systemic diseases, in tumor-like conditions (plaques, splenosis, endometriosis, mesothelial cysts, lymphangiomatosis) and benign tumors (lipoma, benign SFT, schwannoma, solitary extramedullary/extraosseous plasmacytoma). The descriptions are illustrated by corresponding US and CEUS images.

Keywords: benign pleural tumors; benign tumorlike conditions; contrast-enhanced ultrasonography; pleural lesions; transthoracic ultrasonography.

Figure 1

Normal pleura on high resolution TUS. The thoracic wall with the pleural structures is shown with the high-resolution linear transducer (a), and the pleural structures are enlarged in section (b). A: Total reflection of the lung and visceral pleura as hyperechoic interface echoes. B: hypoechoic interpleural space. C: parietal pleura as hyperechoic interface echo. D: hypoechoic extra pleural fat lamella.

Figure 2

Encapsulated pleural effusion. A few months previously, a mitral valve replacement had been performed, which was accompanied by severe complications. The complications included a total right pleural effusion. No pulmonary mass was described preoperatively. In the case of pneumonia, a chest CT was performed, which showed a pleural mass in the right upper lobe. Initially, no distinction was made between a solid lesion and an encapsulated effusion, and image-guided sampling was recommended. A 38 × 24 mm hypoechoic to non-echoic well-circumscribed oval lesion in the right upper lung on high-resolution linear B-mode-ultrasound (a). The lesion did not show any enhancement in the CEUS at any time (b). A solid malignant tumor could, therefore, be excluded. In the US, the findings were, therefore, most likely attributed to an accumulation of fluid, an encapsulated effusion. The lesion was observed during the follow-up examination and regressed spontaneously over time, which was attributed to an encapsulated effusion.

Figure 3

Pleural empyema, pneumonia with pleural effusion, sepsis. Pleural effusion with hypoechoic inhomogeneous internal reflexes and echogenic air reflexes (a). In CEUS, the hypoechoic internal structures are nonenhanced (arrow), i.e., not solid but corresponding to thickened fluid (b). In another transducer position, the empyema is encapsulated, and the pleura is thickened and strongly enhanced on CEUS (arrow) (c).

Figure 4

Septate pleural empyema with many fibrin strands between the atelectatic lung and pleura (a) and formation of a strong chambering with clearly thickened fibrosed hypoechoic pleura (b). re—right thoracic hemispheres.

Figure 5

Pleural thickening and thoracic wall destruction after empyema necessitans . Patient after surgery for cardiac carcinoma with complications including anastomotic insufficiency, mediastinal abscess, and pleural abscess. Endovac (endoscopic vacuum) therapy and percutaneous abscess drainage were performed. Development of swelling of the thoracic wall during the course. In the TUS, inhomogeneous chest wall, hypoechoic lesions, and thickened parietal pleura are demonstrated . Under suspicion of metastasis, a US-guided biopsy was performed several times. This revealed granulomatous inflammation and no evidence of a tumor.

Figure 6

Pleural manifestation of tuberculosis with pleural effusion, markedly thickened hypoechoic pleura, and fibrin strands.

Figure 7

Tuberculous pleurisy with pleural effusion, irregular small pleural thickening, and complex septation.

Figure 8

Hemothorax. Road traffic accident with rib fracture and hemothorax. The TUS shows a pleural effusion with inhomogeneous internal structures (a). On CEUS, after 16 s and 37 s, the atelectatic lung tissue is enhanced (left image side). The remaining nonenhanced structures in the effusion correspond to the blood coagulum (b,c).

Figure 8

Hemothorax. Road traffic accident with rib fracture and hemothorax. The TUS shows a pleural effusion with inhomogeneous internal structures (a). On CEUS, after 16 s and 37 s, the atelectatic lung tissue is enhanced (left image side). The remaining nonenhanced structures in the effusion correspond to the blood coagulum (b,c).

Figure 9

Hemothorax one week after a bicycle accident with a rib fracture. A young man with no history of tumors. Hypoechoic pleural effusion and focal pleural thickening (between the markers). Dist A—distance A.

Figure 10

Development of hypoechoic pleural thickening in a recurrent post-inflammatory pleural effusion (between the markers). The pleura is clearly hyperechoic and thickened above the diaphragm (a). After the effusion has subsided, the hypoechoic thickening of the pleura remains. Between the markers, there is still a narrow amount of fluid in the pleural cavity (b). This suggests that the pleural slide is still preserved. Dist A—distance A.

Figure 11

Lipoma. Female patient with a history of coughing. CT suspected pleural lipoma or liposarcoma. B-mode ultrasound and Color Doppler Imaging (a) revealed a hypoechoic lesion near the heart (color artifacts). CEUS showed sparse but homogenous contrast enhancement (b). Ultrasound-guided biopsy and histological evaluation confirmed lipoma. The biopsy needle is marked with an arrow (c).

Figure 12

Solitary fibrous tumor of the visceral pleura. A lipomatous mass of the right pleura (8 cm) without clinical symptoms was diagnosed 2 years ago. At that time, the mass did not enhance the contrast medium on CT and was interpreted as a cyst. CEUS showed a homogeneous contrast image, albeit very discreet. US-guided transthoracic biopsy was performed. Histology revealed a mixed picture of lipomatous, mesenchymal, and lung tissue. The patient decided against surgical resection. Two years later, the patient suffered from dyspnea, and the mass showed a significant increase in size on CT. The B-mode ultrasound demonstrates a well-defined, hypoechoic tumor (diameter 13 cm) above the diaphragm. The tumor extends on the right side in the costophrenic corner to the mediastinum; there are no signs of infiltration of the lung (a). Color Doppler imaging detects individual large vessels in the tumor (b). The spectral curves were typical for bronchial arteries (not presented here). CEUS (SonoVue^®, 2 mL) showed inhomogeneous enhancement in the bronchial arterial phase (c). The biopsy needle (diameter 1.2 mm) is to be monitored in B-mode US (d). Histology: Solitary fibrous tumor. The tumor was completely removed surgically. Final diagnosis: Solitary fibrous pleural tumor (SFPT) without signs of malignancy. There was no recurrence in the follow-up.

Figure 12

Solitary fibrous tumor of the visceral pleura. A lipomatous mass of the right pleura (8 cm) without clinical symptoms was diagnosed 2 years ago. At that time, the mass did not enhance the contrast medium on CT and was interpreted as a cyst. CEUS showed a homogeneous contrast image, albeit very discreet. US-guided transthoracic biopsy was performed. Histology revealed a mixed picture of lipomatous, mesenchymal, and lung tissue. The patient decided against surgical resection. Two years later, the patient suffered from dyspnea, and the mass showed a significant increase in size on CT. The B-mode ultrasound demonstrates a well-defined, hypoechoic tumor (diameter 13 cm) above the diaphragm. The tumor extends on the right side in the costophrenic corner to the mediastinum; there are no signs of infiltration of the lung (a). Color Doppler imaging detects individual large vessels in the tumor (b). The spectral curves were typical for bronchial arteries (not presented here). CEUS (SonoVue^®, 2 mL) showed inhomogeneous enhancement in the bronchial arterial phase (c). The biopsy needle (diameter 1.2 mm) is to be monitored in B-mode US (d). Histology: Solitary fibrous tumor. The tumor was completely removed surgically. Final diagnosis: Solitary fibrous pleural tumor (SFPT) without signs of malignancy. There was no recurrence in the follow-up.

Figure 13

Solitary fibrous tumor of the parietal pleura of the diaphragm. In an X-ray, a mass was diagnosed adjacent to the diaphragm in the right thoracic hemisphere. (a). The B-mode US shows a well-defined lesion (diameter 10 cm) with solid parts (arrow) and several septa toward the diaphragm. There were no calcifications. No vessels were visible on color Doppler imaging. The lesion appears to be growing out of the parietal pleura of the diaphragm (b). In the dynamic B-mode US examination, normal lung sliding was visible. On CEUS (SonoVue^®), the mass in the late bronchial arterial phase presented a slight enhancement of the solid parts in the marginal area, in the area of the capsule and the septa. The enhancement was of low intensity. The cystic areas are not enhanced. The blood vessels originate from the diaphragm (c). Computed tomography (CT) demonstrated a well-defined cystic lesion of the pleura in the region of the diaphragm in the right thoracic hemisphere (d). The surgical findings showed a space-occupying lesion growing out of the diaphragm towards the lung (e). The histological diagnosis was a solitary fibrous diaphragmatic tumor without signs of malignancy. There was no recurrence in the follow-up. X-ray and CT images are courtesy of Prof. Lenz, Radiology Department Klinikum am Steinenberg Reutlingen. Surgical specimen courtesy Prof. Zimmermann, Clinic for Visceral Surgery, Klinikum am Steinenberg Reutlingen.

Figure 13

Solitary fibrous tumor of the parietal pleura of the diaphragm. In an X-ray, a mass was diagnosed adjacent to the diaphragm in the right thoracic hemisphere. (a). The B-mode US shows a well-defined lesion (diameter 10 cm) with solid parts (arrow) and several septa toward the diaphragm. There were no calcifications. No vessels were visible on color Doppler imaging. The lesion appears to be growing out of the parietal pleura of the diaphragm (b). In the dynamic B-mode US examination, normal lung sliding was visible. On CEUS (SonoVue^®), the mass in the late bronchial arterial phase presented a slight enhancement of the solid parts in the marginal area, in the area of the capsule and the septa. The enhancement was of low intensity. The cystic areas are not enhanced. The blood vessels originate from the diaphragm (c). Computed tomography (CT) demonstrated a well-defined cystic lesion of the pleura in the region of the diaphragm in the right thoracic hemisphere (d). The surgical findings showed a space-occupying lesion growing out of the diaphragm towards the lung (e). The histological diagnosis was a solitary fibrous diaphragmatic tumor without signs of malignancy. There was no recurrence in the follow-up. X-ray and CT images are courtesy of Prof. Lenz, Radiology Department Klinikum am Steinenberg Reutlingen. Surgical specimen courtesy Prof. Zimmermann, Clinic for Visceral Surgery, Klinikum am Steinenberg Reutlingen.

Figure 13

Solitary fibrous tumor of the parietal pleura of the diaphragm. In an X-ray, a mass was diagnosed adjacent to the diaphragm in the right thoracic hemisphere. (a). The B-mode US shows a well-defined lesion (diameter 10 cm) with solid parts (arrow) and several septa toward the diaphragm. There were no calcifications. No vessels were visible on color Doppler imaging. The lesion appears to be growing out of the parietal pleura of the diaphragm (b). In the dynamic B-mode US examination, normal lung sliding was visible. On CEUS (SonoVue^®), the mass in the late bronchial arterial phase presented a slight enhancement of the solid parts in the marginal area, in the area of the capsule and the septa. The enhancement was of low intensity. The cystic areas are not enhanced. The blood vessels originate from the diaphragm (c). Computed tomography (CT) demonstrated a well-defined cystic lesion of the pleura in the region of the diaphragm in the right thoracic hemisphere (d). The surgical findings showed a space-occupying lesion growing out of the diaphragm towards the lung (e). The histological diagnosis was a solitary fibrous diaphragmatic tumor without signs of malignancy. There was no recurrence in the follow-up. X-ray and CT images are courtesy of Prof. Lenz, Radiology Department Klinikum am Steinenberg Reutlingen. Surgical specimen courtesy Prof. Zimmermann, Clinic for Visceral Surgery, Klinikum am Steinenberg Reutlingen.

Figure 14

Schwannoma. A male patient with a history of smoking (20 packyears) was hospitalized for diagnostic confirmation of an unclear asymptomatic pleural lesion that has been described in a CT scan. Ultrasound revealed a small, smooth, roundish tumor at the chest wall/parietal pleura (a) with normal lung sliding and no signs of infiltrative growth. CEUS showed good and relatively homogeneous arterial contrast enhancement with a small central notch. The time after application of the contrast medium is indicated at the bottom of the image: A (0:16 s/ 0:30 s/ 1:04 min) (b–d). Histology from a US-guided needle biopsy confirmed a schwannoma. The illustration in B-mode-US shows the US-guided biopsy with corresponding digital planning (blue dots) (e).

Figure 14

Schwannoma. A male patient with a history of smoking (20 packyears) was hospitalized for diagnostic confirmation of an unclear asymptomatic pleural lesion that has been described in a CT scan. Ultrasound revealed a small, smooth, roundish tumor at the chest wall/parietal pleura (a) with normal lung sliding and no signs of infiltrative growth. CEUS showed good and relatively homogeneous arterial contrast enhancement with a small central notch. The time after application of the contrast medium is indicated at the bottom of the image: A (0:16 s/ 0:30 s/ 1:04 min) (b–d). Histology from a US-guided needle biopsy confirmed a schwannoma. The illustration in B-mode-US shows the US-guided biopsy with corresponding digital planning (blue dots) (e).

Figure 15

Schwannoma. As an “incidental finding”, a mass (diameter 3 cm) was found in the chest X-ray in the region of the thoracic wall, which corresponded to a solid formation on CT. The B-mode US shows a homogeneous, well-defined mass below the scapula that is positioned on the parietal pleural line (a). The normal lung slides over the mass. On dynamic US, lung sliding was seen on B-mode US and in color Doppler Imaging. Some vessels inside the tumor are visible (b). On CEUS, the lesion demonstrated mostly homogeneous enhancement in the late bronchial arterial phase. Some small areas were non-enhanced (c). The vascularization originated from the intercostal arteries. The lesion showed a washout only very late. US-guided sampling with a BioPince needle (1.2 mm) (Argon Medical devices company, Plano, TX, USA) was performed. Histology: Schwannoma, no signs of malignancy. Distanz—diameter.

Figure 16

Solitary extramedullary plasmacytoma histologically confirmed. Male patient with weight loss. Chest CT revealed a right paravertebral mass in relation to the chest wall, pleura, and lung. Ultrasonography showed a highly hypoechoic, almost non-echoic lesion. This displaces the lung. An echogenic reflex is seen centrally, and a vascular structure is seen in the color Doppler Imaging (a). Multiple macrovessels are delineated in the power Doppler and bidirectional power Doppler (b,c). On CEUS, the first signals arrive at 13 s in the bronchial arterial phase (d). The lesion is homogeneously enhanced in the bronchial arterial phase (d–f). Histologic confirmation was performed by percutaneous US-guided needle biopsy. T1- time after application of ultrasound contrast agent.

Figure 16

Solitary extramedullary plasmacytoma histologically confirmed. Male patient with weight loss. Chest CT revealed a right paravertebral mass in relation to the chest wall, pleura, and lung. Ultrasonography showed a highly hypoechoic, almost non-echoic lesion. This displaces the lung. An echogenic reflex is seen centrally, and a vascular structure is seen in the color Doppler Imaging (a). Multiple macrovessels are delineated in the power Doppler and bidirectional power Doppler (b,c). On CEUS, the first signals arrive at 13 s in the bronchial arterial phase (d). The lesion is homogeneously enhanced in the bronchial arterial phase (d–f). Histologic confirmation was performed by percutaneous US-guided needle biopsy. T1- time after application of ultrasound contrast agent.