Chapter 9
Lung tumours
Christian Görg1, Corinna Trenker1 and Andreas Schuler2
1Universitatsklinikum Giessen und Marburg, Marburg, Germany. 2Alb Fils Kliniken, Zentrum Innere Medizin, Helfenstein Klinik Geislingen, Geislingen, Germany.
Correspondence: Christian Görg, Universitatsklinikum Giessen und Marburg – Standort Marburg. E-mail: goergc@med.uni-marburg.de
The diagnostic value of TUS of lung tumours, especially bronchial carcinomas, is limited and dependent on the localisation of the tumour. Focused clinical use is to be distinguished in the context of primary diagnosis, staging, therapy response and tumour growth. Symptom-oriented practice is important at the bedside for palliative patients, in point-of-care sonography, in the emergency room and in intensive care units. Different US-based procedures, such as transcutaneous US, EUS and EBUS are used for distinct approaches to lung tumours. B-mode imaging, colour Doppler sonography, CEUS and US-controlled interventions are the sonographic modalities used in daily clinical practice and for special clinical questions. In special clinical indications, US is the primary guideline diagnostic procedure. Transthoracic LUS is limited by physical factors such as absorption and reflection and, in principle, by a high interobserver variability, as well as differences in device and examining competence.
Cite as: Görg C, Trenker C, Schuler A. Lung tumours. In: Laursen CB, Rahman NM, Volpicelli G, eds. Thoracic Ultrasound (ERS Monograph). Sheffield, European Respiratory Society, 2018; pp. 115–128 [https://doi.org/10.1183/2312508X.10006817].
Lung tumours are amongst the most frequently seen malignant tumours in the world and are one of the most common causes of cancer death [1]. Smoking is a major risk factor. Clinical symptoms are uncharacteristic and include cough, dyspnoea, haemoptysis, weight loss and occasional chest pain. Diagnostic procedures, therapy and follow-up are presented in the current guidelines [2]. A whole-body PET (PET-CT) in combination with an all-body CT, a radiographic thorax examination and EBUS, is part of the standard diagnostic procedure [3]. Transoesophageal US (EUS), angiography, MRI, mediastinoscopy and ultimately transcutaneous sonography are additional methods. The aims of the diagnostic procedures are correct tumour diagnosis and characterisation of the cancer, including TNM (tumour, node, metastases) classification [4–7]. In the context of diagnosis and therapy of lung tumours, transcutaneous LUS is used for primary tumour diagnosis and differential diagnosis, histological confirmation, staging, therapy response, aftercare and detection of tumour- or therapy-associated complications [8, 9]. The following modalities are used: B-mode imaging [10–12], colour Doppler sonography (CDS) [13, 14], CEUS [15–18] and US-guided biopsy [19, 20]. The benefits of US examination are: high spatial resolution, real-time conditions, the absence of radiation exposure [21], arbitrary repeatability, and the possibility of bedside examination. Last but not least, ultrasound examination as a dialogue is important for tumour patients [22]. LUS is limited by interobserver variability, a lack of overview, and physically induced limitations on the thorax caused by sound reflexion behind bony structures and the air-filled lung [23]. According to the diagnostic guidelines, the following indications for US can be distinguished.
1) Visualisation and characterisation of peripheral pleural-based lung tumours [24] with regard to thoracic wall infiltration [25, 26], the possibility of histological diagnosis with percutaneous tumour biopsy [27–29], detection of pleural effusion [30–32] and initiation of paracentesis (T-Stage) [33].
2) Visualisation and characterisation of the peripheral collar [4, 34, 35] and mediastinal lymph nodes with percutaneous and endosonographic US, and possibly US-guided biopsy (N-Stage).
3) Specific presentation, characterisation and, where appropriate, histological preservation of otherwise unclear tumour formations within the context of staging procedures (M-Stage) [9, 36].
Lung sonography where a lung tumour is suspected
In the diagnosis and differential diagnosis of bronchial carcinoma, CT of the thorax is the standard procedure for T-classification, and where possible, should be taken as the basis of US examination. An indication for transthoracic LUS does not exist in general, but can be deployed in a focused manner, according to the clinical questions. First, basic and sonographic criteria of lung tumour assessment will be presented. Subsequently, sonographic findings will be presented with regard to the clinical questions.
Lung sonography where a lung tumour is suspected is limited and depends on the presentation of the primary tumour. In general, peripheral lung tumours can be differentiated from central tumours. While peripheral tumours can be visualised due to contact with the pleural/thoracic wall, central lung tumours can only be detected with associated obstructive atelectasis or pleural effusion with compression-induced atelectasis (figure 1) [37, 38].
Figure 1. Patient with lung consolidation primarily suspected of pneumonia. Histological examination due to bronchoscopy revealed bronchioloalveolar nonsmall cell lung cancer. a) CXR shows a right-sided lung consolidation. b) CT shows a right-sided homogeneous lung consolidation. c) B-mode US shows a homogeneous hypoechoic lung consolidation without airbronchogram. d) Colour Doppler sonography shows marked regular vessels. e) Spectral curve analysis shows a high impedant flow signal due to pulmonary arterial supply. f) CEUS shows marked pulmonary arterial enhancement in the arterial phase (10 s). g) CEUS shows marked enhancement in the parenchymal phase (1 min).
In B-mode imaging, pulmonary consolidations are characterised by their size, margins and echogenicity, and the homogeneity of the lung tissue. In CDS, vascularisation is evaluated by the extent of the CDS (missing, reduced, marked flow signals) and the vascular patterns (regular, disordered vessels) [39]. With spectral curve analysis (SCA), high-impedance can be differentiated from low-impedance flow signals in the consolidated lung; high-impedance flow signals can be assigned to the pulmonary arteries and low-impedance flow signals to the bronchial arteries [40–42]. Tumour neoangiogenic capacity is attributed to the bronchial arteries [43–46].
CEUS of the thorax is possible and has to be performed according to the guidelines of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) [15]. The first evaluation criterion is the “time to enhancement”. Pulmonary artery supply of a pulmonary lesion can be determined by early arterial enhancement before systemic vascular enhancement. Bronchial artery supply is characterised by delayed arterial enhancement at the same time as systemic vascular presentation. Further CEUS evaluation criteria are the “extent of enhancement” (none, reduced, marked) and the “homogeneity of enhancement” (homogeneous, inhomogeneous). These CEUS patterns may be analysed in the arterial and parenchymal phase [16, 18].
Another procedure is US-guided biopsy of thoracic tumours [19, 20, 47]. Differentiation is made between the size of the biopsies (core needle: >1 mm needle diameter; fine needle: <1 mm needle diameter). Depending on clinical indication, pleural effusion-paracentesis (diagnostic, therapeutic) and catheter drainages (pig-tail catheter, subtunneled continuous drainage) can be differentiated.
The following clinical questions have to be answered through focused LUS examination.
Is there a peripheral lesion suspected for bronchial carcinoma?
In everyday clinical practice, LUS is often used as primary diagnostic imaging. CT of the thorax is necessary where there is clinical and sonographical suspicion of a lung tumour. Primarily, peripheral and pulmonary consolidations are differentiated with LUS (figure 1).
Peripheral lung tumours are usually homogeneously hypoechoic in B-mode imaging. Necrotic tissue can be observed as anechoic areas within the consolidated lung [37]. The margins are variable but usually sharp. Definite differentiation from metastatic consolidations is not possible, although lung metastases are mostly characterised by a round shape. In CDS, peripheral lung tumours have a predominantly reduced disordered vascular pattern [39] with missing flow signal in areas of necrosis. In the SCA, a low-impedance bronchial artery vascular supply is mostly present [48]. In peripheral lung tumours, CEUS shows a systemic contrast media inflow in the arterial phase with a reduced mostly inhomogeneous enhancement [16, 18]. An airbronchogram is characteristic for pneumonic consolidations and untypical for lung carcinomas but nevertheless is sometimes seen in rare types of lung cancer [49, 50], such as subgroups of pulmonary adenocarcinoma, bronchioloalveolar carcinoma and pulmonary lymphoma [51]. These “pitfalls” are also characterised in the CDS by a regular marked vascular supply and show a highly impeded pulmonary artery vascularisation. In CEUS, these atypical forms of malignant consolidation imply an early contrast media inflow, and a marked and homogeneous contrast media accumulation, which cannot be distinguished from an inflammatory consolidation [49, 52]. A fluid bronchogram is predominantly characteristic of obstructive atelectatic pulmonary consolidations due to centrally located pulmonary carcinomas [37, 38].
Can a central tumour lesion be seen and differentiated from associated atelectasis?
Central lung tumours can only be sonographically detected in cases of a simultaneous pulmonary atelectasis caused by central tumour-induced bronchus occlusion (obstructive atelectasis) or in cases of pleural effusion caused by compression atelectasis. In obstructive atelectasis, B-mode imaging may show sharp margins and a fluid bronchogram, and does not show an airbronchogram. Atelectasis, either by compression or obstruction, shows a regular tree-like marked vascular presentation in the CDS with highly impeded pulmonary artery flow signals in SCA. In advanced disease with signs of tumour occlusion of pulmonary artery branches, atelectasis may show a bronchial artery vascular supply [13, 14]. Discrimination of the central tumour from atelectasis is not always possible with B-mode imaging, but with the aid of CEUS, the central lung tumour can be distinguished from the atelectasis by reduced contrast media enhancement [53] at a frequency comparable to CT (figure 2). In cases of frustrating bronchoscopic histology, transcutaneous tumour biopsy through atelectasis may be desired. In this context, the atelectasis acts as an “acoustic window” for visualisation of the central lung cancer [38].
Figure 2. Patient with lung consolidation and histologically proven nonsmall cell lung cancer. a) CXR shows a left-sided central lung consolidation. b) CT shows a left-sided central tumour with suspected obstructive atelectasis. c) B-mode US shows a homogeneous hypoechoic lung consolidation without airbronchogram. The central tumour cannot be distinguished from the atelectatic tissue. d) CEUS shows reduced enhancement of the central tumour in the parenchymal phase, in comparison to atelectasis.
Is there thoracic wall infiltration?
Thorax wall infiltration classifies a lung tumour as T3 [2]. This does not limit surgical treatment but is important for operation planning. B-mode US represents the imaging method of choice here due to the high spatial resolution of US but mainly because it allows the possibility of the real-time examination [25, 26]. Criteria for thoracic wall infiltration are: absent pulmonary sliding to the thoracic wall (“fixed lung”); interruption of the pleural line; detection of continuous tumour infiltration into the thoracic wall; tumour vascularisation of the lesion via bronchial artery tumour neoangiogenesis [54]; and additional systemic tumour vascularisation from the intercostal arteries [42]. Tumour localisation in the apex of the lung is known as a Pancoast tumour (figure 3).
