Pictorial essay of radiological features of benign intrathoracic masses

Abstract

With increased exposure of patients to routine imaging, incidental benign intrathoracic masses are frequently recognized. Most have classical imaging features, which are pathognomonic for their benignity. The aim of this pictorial review is to educate the reader of radiological features of several types of intrathoracic masses. The masses are categorized based on their location/origin and are grouped into parenchymal, pleural, mediastinal, or bronchial. Thoracic wall masses that invade the thorax such as neurofibromas and lipomas are included as they may mimic intrathoracic masses. All examples are illustrated and include pulmonary hamartoma, pleural fibroma, sarcoidosis, bronchial carcinoid, and bronchoceles together with a variety of mediastinal cysts on plain radiographs, computed tomography (CT) and magnetic resonance imaging (MRI). Sometimes a multimodality approach would be needed to confirm the diagnosis in atypical cases. The study would include the incorporation of radionuclide studies and relevant discussion in a multidisciplinary setting.

Keywords: Intrathoracic masses; pulmonary mass; radiology.

Figure 1

CXR of a 27-year-old female (nonsmoker) showing a solitary well-defined nodule in the left upper zone (arrow). CT further characterizes the opacity by demonstrating fat content within the mass highly suggested of a hamartoma. No biopsy was taken. The nodule remains stable 3 years later. CXR = Chest X-ray, CT = computed tomography

Figure 2

CXRs from two different patients showing the characteristics popcorn calcification of a hamartoma

Figure 3

A 35-year-old with known sarcoidosis. Her chest radiograph demonstrates the “Garland sign”—Bilateral hilar and right paratracheal lymphadenopathy. Coronal CT confirms the findings. No lung parenchymal changes are seem

Figure 4

Sarcoidosis in a 56-year-old female patient demonstrating classical eggshell hilar (1) calcification. Note the reticulonodular parenchymal changes of perilymphatic distribution in the middle and upper lobes (2)

Figure 5

Silicosis massive pulmonary fibrosis (MPF) symmetrical bilateral opacities of more than 1 cm, formed by nodule coalescence forming mass that may even cavitate (*)

Figure 6

Intrapulmonary lymph node: Incidental finding of a small, oval-shaped parenchymal opacity in the right lower lobe. The appearances are classically those of intrapulmonary lymph node and no further actions are required

Figure 7

Rheumatoid nodules: Long standing solitary pulmonary nodule in the periphery of the left lower lobe of a 60-year-old male patient with known rheumatoid arthritis. This is likely a rheumatoid nodule

Figure 8

Rheumatoid nodules: PA CXR of a 53-year-old man with seropositive rheumatoid arthritis being treated with rituximab showing a nodule in the right upper lobe (red arrow) and a cavitating nodule (yellow arrow) in the left upper lobe on a background of multinodularity suggestive of Kaplan's syndrome. PA = Posteroanterior

Figure 9

Note the solid pleural-based nodule, associated with a small pleural effusion (pulmonary infarct). The patient had a travel-related deep venous thrombosis that presented with pleuritic, left-sided chest pain

Figure 10

Septic emboli. Gas gangrene of the foot in a 49-year-old woman with type II diabetes mellitus, showing gas within the soft tissues of the foot (1), also elegantly shown by gas within the soft tissues of the foot on ultrasound examination. There are multiple pleural-based nodules on the CXR suggestive of septic emboli (3)

Figure 11

Axial CT images from the same patient as in Figure 10 with a gas gangrene of the foot showing multiple, pleural-based nodules due to septic emboli with evidence of early cavitation in one of the nodules (arrow)

Figure 12

CXR showing a thick-walled cavity with an air-fluid level due to a cavitating pulmonary infarct. The cavity is indistinguishable from other cavities such as cavitating neoplasia. To achieve a diagnosis, the history and the radiological evolution is important. This patient was a known pulmonary infarct, which subsequently cavitated

Figure 13

Wegener's granulomatosis: CXR in a patient with Wegener's granulomatosis showing a thick-walled cavity in the left upper lobe and patchy bilateral basal shadowing. CT confirmed multiple ground glass changes in keeping with pulmonary hemorrhage secondary to the disease

Figure 14

Pleural fibroma: Incidental pleural-based mass in the right costophrenic angle in a 65-year-old male presenting with shortness of breath. CT confirms the presence of a well-defined homogenous right lower parietal pleural mass measuring 6 cm × 3 cm with focal calcification

Figure 15

A pleural fibroma should not be confused with a mesothelioma, note the calcified pleural plaque, a pleural-based mass invading the intercostal space (arrow) in this patient with previous asbestos exposure

Figure 16

Splenosis: Incidental finding on a chest radiograph of a left-sided, pleural-based mass. CT confirms this and also other pleural nodularities, with the absence of a spleen. Further history was obtained and this patient was noted to have been involved in a blast injury. Splenic injuries were therefore suspected

Figure 17

Splenic scintigraphy SPECT/CT study scans confirm intense uptake in the left hemithorax pleural nodularities. The appearances are those of post-traumatic abdominal and intrathoracic splenosis. SPECT = Single-photon emission CT

Figure 18

Soft and calcified pleural plaques, due to asbestos exposures. Soft plaques cannot be reliably differentiated from a mesothelioma without a biopsy

Figure 19

Loculated interlobular pleural effusion or pulmonary pseudotumor; also called vanishing tumor

Figure 20

Loculated pleural effusion: A smoothly-defined, right, pleural-based mass is demonstrated on the chest radiograph. On CT, this “mass” was noted to be of fluid density. Appearances are in keeping with a loculated pleural effusion

Figure 21

Round atelectasis occurs when there is unfolding of redundant pleura. This may give a false, mass-like appearance. It is most commonly associated with asbestos-related disease, but it may arise from a variety of chronic pleural conditions such as infection, uraemia, therapeutic pneumothorax in the treatment of tuberculosis, pulmonary infarction, or heart failure and is usually asymptomatic. The images show a rounded atelectasis in association with pleural thickening secondary to asbestoses exposure

Figure 22

Chest wall lipoma: Examples of chest wall lipomas on differing imaging modalities. The chest radiograph (1) demonstrates a well-defined, smooth, right lateral chest wall mass. Ultasound scan (2) demonstrates a homogeneous mildly echogenic ovoid structure and T1-weighted MR scan (3) demonstrated a homogeneous. MR = Magnetic resonance

Figure 23

Carcinoid: CT in a breathless 70-year=old gentleman demonstrates the presence of an endobronchial lesion in the right bronchus intermedius. An endbronchial ultrasound (EBUS) was performed and samples obtained. This was later shown to be a bronchial carcinoid

Figure 24

On a CXR bronchogenic cysts usually appear as soft-tissue density rounded structures. As the cysts may contain calcium oxalate, dependent layering of calcific density material may occasionally be seen as seen on the CXR. CT is better able to detect calcium oxalate (milk of calcium) layering dependently as shown

Figure 25

Bronchogenic cyst: Well-defined, left hilar shadows seen on the chest radiograph. CT shows well-defined 3.5 × 24 cm uniformly low attenuation (HU 34) lesion arising from the posterior mediastinum in keeping with a bronchogenic cyst

Figure 26

Bronchocele: Chest radiograph performed in asthmatic 50-year-old male demonstrated branching tubular structures in the left lower zone. An incidental left upper zone nodule has remained unchanged for many years

Figure 27

Bronchocele: CT confirms the presence of dilated and ectatic left lower lobe bronchioles with evidence of mucus impaction. Appearances are suggestive of bronchocele secondary to asthma and increased mucus production

Figure 28

This patient presented with severe right shoulder pain. The CXR and T1- and T2-weighted axial images show features of a hydatid cyst in the right superior sulcus (Images courtesy: Shyam Sunder)

Figure 29

Retrosternal goiter: Axial and sagittal CT images show heterogeneous, well-defined, 6.5 × 24.0 cm, right retrosternal goiter with speckles of calcification

Figure 30

Retrosternal thyroid: Chest radiograph demonstrates a soft tissue mass in the superior right mediastinum causing deviation of the trachea to the contralateral left. CT confirms a heterogeneous 5 cm × 4 cm right retrosternal thyroid gland

Figure 31

Retrosternal thyroid: CXR demonstrates a large soft tissue mass in the superior right mediastinum causing deviation and compression of the trachea and displacement of the mediastinum to the contralateral left. CT confirms a heterogeneous right retrosternal thyroid gland. The patient presented with stridor at surgery; a partial thyroidectomy confirmed benign retrosternal goiter

Figure 32

Pericardial cyst: Axial and sagittal views of an arterial contrast-enhanced scan through the thorax of another patient demonstrated a 3.5 cm × 2.0 cm left pericardial cyst in the region of the lingual

Figure 33

Pericardial cyst: Axial T1- and T2-weighted MRI showing typical fluid signal in the pericardial cyst with occasional high signal on T1-weighted images (not shown). MRI = MR imaging

Figure 34

A 45-year-old man recently diagnosed with myasthenia gravis undergoes CT thorax. This demosntrated a 2.5 cm × 3.5 cm, well-defined homogenous anterior mediastinal mass in keeping with a thymoma

Figure 35

Thymoma: Axial CT shows a well-defined homogenous anterior mediastinal mass in a patient that presented with myasthenia gravis. FDG-PET showing uptake within the tumor. A thymoma was confirmed at surgery. FDG-PET = Fluorodeoxygenase positron emission tomography

Figure 36

This male patient in the mid-30s presented with clinical features of myasthenia gravis. The axial and sagittal CT showed a mass in the anterior mediastinum, with slight surface tumor irregularity and areas of necrosis. At surgery a malignant thymoma was confirmed

Figure 37

STIR sequence and T2-weighted axial and coronal images through the mid mediastinum showing diffuse symmetric and smooth enlargement of the thymus gland due to thymic hyperplasia. STIR = Short TI inversion recovery

Figure 38

Axial CT through the anterior mediastinum shows a lobulated thymic mass with low attenuation areas in keeping with thymic cysts. FDG-PET shows no uptake within the cysts

Figure 39

Cystic thymoma: Axial T1, T2, and post-gadolinium MRI showing characteristic features of a cystic thymoma without intrinsic contrast enhancement

Figure 40

CXR shows a well-defined, smooth, lower right paravertebral mass with close association with spinal canal (axial CT) in keeping with a benign neurogenic tumor

Figure 41

Extramedullary hematopoiesis usually occurs in association with hematological disorders and normally involves the reticuloendothelial system, including the liver, spleen, and lymph nodes. This patient had a beta thalassemia. Note the paravertebral location of the extramedullary hematopoiesis

Figure 42

Noncontrast axial CT, T2-weighted MR, and post-contrast CT chest shows features of a chronic calcific hematoma