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Pulmonary Neoplasms
Evaluation of the Solitary Pulmonary Nodule
Evaluation of the Solitary Pulmonary Nodule
Definition
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This is defined as a solitary circumscribed pulmonary opacity with no associated pulmonary, pleural, or mediastinal abnormality ▸ it measures < 3 cm in diameter
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Many are discovered incidentally (but up to 40% may be malignant)
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<10% are due to a solitary pulmonary metastasis
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Benign intrapulmonary lymph nodes: nodules <15 mm from the pleural surface ▸ ellipsoid in shape, usually connected to the pleural surface by a fine linear opacity
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Ground-glass nodules :
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Ground-glass density: focal area of increased lung attenuation (well or poorly defined) through which normal structures can be seen
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Pure ground-glass nodule: no soft tissue component
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Part solid ground-glass nodule: a solid component obscuring lung architecture
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Differentiation Between Benign and Malignant Masses
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The two primary criteria are the rate of growth (or stability over time) and the attenuation of the nodule ▸ the patient's age is also a significant distinguishing feature (a carcinoma is only seen in < 1% of patients < 35 years old)
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Rate of growth/stability over time: benign lesions invariably have a doubling time of < 1 month or > 18 months (bronchoalveolar carcinomas are an exception in that they may have very slow growth rates) ▸ bronchial carcinomas usually have a doubling time of between 1 and 18 months
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Attenuation/enhancement: a dense central nidus or lamellated calcification indicates a granulomatous process (e.g. tuberculosis, histoplasmosis) ▸ irregular ‘popcorn’ calcification suggests a hamartoma ▸ fat is virtually diagnostic of a hamartoma ▸ a lack of enhancement (<15HU) following IV contrast medium is indicative of benignity
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Granular calcification is seen on CT in up to 7% of carcinomas (and can represent either tumour calcification or a granuloma engulfed by tumour) ▸ eccentric or stippled calcification within soft tissue may indicate malignancy
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A mixture of soft tissue and ground-glass attenuation nodules is more likely to be malignant than soft tissue nodules alone
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Size: this is of little diagnostic value ▸ most benign nodules are <2 cm ▸ round, flat or tubular nodules tend to be benign
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Margins: a well-defined mass with a smooth pencil sharp margin is likely to be benign ▸ carcinomas typically have ill-defined margins which are irregular, spiculated, or lobulated and may exhibit umbilication or a notch – unfortunately all these features can be seen with benign disease
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FDG-PET
This is useful for nodules >1 cm ▸ a positive result is 97% sensitive and 82% specific for malignancy
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False-positive result: this can be secondary to an infectious or inflammatory processes (e.g. TB, sarcoid or rheumatoid nodules)
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False-negative result: this can occur if a nodule is <1 cm ▸ it can also occur if the nodule is due to a carcinoid tumour or a slow-growing adenocarcinoma subtype
Recommendations for the management of subsolid pulmonary nodules detected at CT: a statement from the Fleischner Society
| Nodule type | Management recommendations | Additional remarks |
|---|---|---|
| Solitary pure GGNs | ||
| ≤5 mm | No CT follow-up required | Obtain contiguous 1-mm-thick sections to confirm that nodule is truly a pure GGN |
| >5 mm | Initial follow-up CT at 3 months to confirm persistence then annual surveillance CT for a minimum of 3 years | FDG PET is of limited value, potentially misleading, and therefore not recommended |
| Solitary part-solid nodules | Initial follow-up CT at 3 months to confirm persistence. If persistent and solid component <5 mm, then yearly surveillance CT for a minimum of 3 years. If persistent and solid component ≥5 mm, then biopsy or surgical resection | Consider PET/CT for part-solid nodules >10 mm |
| Multiple subsolid nodules | ||
| Pure GGNs ≤5 mm | Obtain follow-up CT at 2 and 4 years | Consider alternate causes for multiple GGNs ≤5 mm |
| Pure GGNs >5 mm without a dominant lesion(s) | Initial follow-up CT at 3 months to confirm persistence and then annual surveillance CT for a minimum of 3 years | FDG PET is of limited value, potentially misleading, and therefore not recommended |
| Dominant nodule(s) with part-solid or solid component | Initial follow-up CT at 3 months to confirm persistence. If persistent, biopsy or surgical resection is recommended, especially for lesions with >5 mm solid component | Consider lung-sparing surgery for patients with dominant lesion(s) suspicious for lung cancer |
Note—These guidelines assume meticulous evaluation, optimally with contiguous thin sections (1 mm) reconstructed with narrow and/or mediastinal windows to evaluate the solid component and wide and/or lung windows to evaluate the nonsolid component of nodules, if indicated. When electronic calipers are used, bidimensional measurements of both the solid and ground-glass components of lesions should be obtained as necessary. The use of a consistent low-dose technique is recommended, especially in cases for which prolonged follow-up is recommended, particularly in younger patients. With serial scans, always compare with the original baseline study to detect subtle indolent growth.
Lung Cancer: Radiological Features
Lung Cancer: Radiological Features
Definition
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SCLC: small (oat) cell carcinoma
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This originates from submucosal neuroendocrine cells ▸ it rapidly spreads haematogenously and to the lymph nodes ▸ it behaves as a systemic disease and is usually disseminated at presentation
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NSCLC: non-small cell lung cancer
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Squamous cell carcinomas: arises from the proximal airway epithelium
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Large cell carcinomas: atypical cells that appear ‘large’ under the microscope
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Adenocarcinomas: arising from the bronchial glands
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Risks: tobacco smoke (20- to 30-fold increased risk) – has the greatest association with squamous cell carcinomas and weakest association with bronchoalveolar carcinomas ▸ asbestos exposure, interstitial pulmonary fibrosis and radiotherapy are additional risks
Clinical presentation
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Asymptomatic (25%): asymptomatic peripheral tumours are more likely to be incidental findings and surgically resectable
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Symptomatic: recurrent pneumonia ▸ cough ▸ wheeze ▸ haemoptysis
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Paraneoplastic syndromes: inappropriate ADH secretion ▸ Cushing's syndrome (ACTH) ▸ carcinoid syndrome ▸ hypercalcaemia (PTH)
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Poor prognostic features: hoarseness ▸ chest pain ▸ brachial plexus neuropathy or Horner's syndrome (due to a Pancoast's tumour) ▸ SVC obstruction ▸ dysphagia
Radiological features
Peripheral tumours
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The majority are spherical or oval in shape ▸ lobulated masses can occur due to uneven growth rates ▸ there may be a ‘corona radiata’ due to numerous fine strands radiating into the lung ▸ a bronchocele or mucoid impaction can be seen distal to an obstructing carcinoma ▸ collapse and consolidation is less commonly seen than with central tumours
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Cavitation with irregular thick walls (≥8 mm) ± fluid levels (particularly squamous tumours)
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Calcification is rare (6–10%) and may represent engulfed granulomatous disease ▸ amorphous or cloud-like calcification can be seen with dystrophic tumour calcification (10%)
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Air bronchograms are rare but can be seen with adenocarcinoma
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Ground-glass attenuation is associated with a higher risk of malignancy (and commonly seen with lepidic or invasive mucinous adenocarcinoma)
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Central tumours
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Collapse or consolidation can be seen peripheral to the tumour (due to bronchial narrowing ± hilar enlargement) ▸ any peripheral collapsed lung will enhance more than a central tumour ▸ collateral air drift may prevent some post-obstructive changes
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‘ Golden S’ sign : a fissure may show a central bulge due to collapse around a central tumour
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Hilar enlargement (N1-N3)
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This is a common presenting feature and may reflect a proximal central tumour, lymphadenopathy or consolidated lung ▸ extensive hilar and mediastinal lymphadenopathy is typical of small cell tumours ▸ simple pneumonias rarely cause hilar adenopathy
Chest wall invasion (T3)
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This does not preclude surgical resection (although it adversely affects the prognosis)
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CT: assessment is unreliable (with local chest wall pain remaining the most specific indicator) ▸ contact with or a thickened pleura does not necessarily indicate invasion ▸ a clear extrapleural fat plane is helpful but not definitive ▸ reliable signs include clear-cut bone destruction or a large soft tissue mass
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MRI: this is better than CT in selected cases ▸ it is the optimal modality for demonstrating the extent of a superior sulcus tumour
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Transthoracic ultrasound: this is an accurate technique
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99m Tc radionuclide skeletal scintigraphy: this is sensitive (and may detect bone invasion before plain radiography) ▸ PET-CT is now the technique of choice for distant spread
Mediastinal invasion (T4)
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CT/MRI indicators: visible tumour deep within the mediastinal fat (mediastinal contact alone is not enough to diagnose invasion) ▸ encasement of the mediastinal vessels, oesophagus, or proximal mainstem bronchi ▸ SVC obstruction ▸ an elevated hemidiaphragm (indicating phrenic nerve involvement)
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Criteria for resectability: < 3 cm of contact with the mediastinum ▸ < 90° of circumferential contact with the aorta ▸ a visible mediastinal fat plane between the mass and any vital mediastinal structure
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Irresectability: tumours obliterating fat planes or showing greater contact than that described above (although less certain)
Bone involvement (M1)
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Direct rib or spine invasion ▸ haematogenous osteolytic bone metastases ▸ hypertrophic osteoarthopathy
New classification for adenocarcinomas
| Premalignant | Malignant |
|---|---|
| Atypical adenomatous hyperplasia | Minimally invasive adenocarcinoma |
| Adenocarcinoma in situ | predominantly lepidic growth pattern |
| lepidic growth pattern (no solid components) | ≤3 cm |
| pure ground-glass opacity on CT | invasive component <5 mm |
| subsolid nodules on CT | |
| Lepidic predominant adenocarcinoma | |
| >5 mm invasion | |
| previously known as non-mucinous bronchoalveolar carcinoma | |
| Invasive mucinous adenocarcinoma | |
| previously known as mucinous bronchoalveolar carcinoma |
Lung Cancer: Pearls
Lung Cancer: Pearls
Pleural effusions (M1a)
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They may occur due to direct spread, lymphatic involvement, or tumour emboli (an adenocarcinoma may cause lobular pleural thickening indistinguishable from a malignant mesothelioma)
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A pleural effusion designates a tumour as M1a (unless clinically there is another cause and the pleural cytology is negative)
Lepidic predominant adenocarcinoma/invasive mucinous adenocarcinoma (formerly bronchoalveolar carcinoma)
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This can appear as a solitary lobulated or spiculated pulmonary mass with air bronchograms and cavitation ▸ it may also appear as an ill-defined opacity resembling a pneumonia, homogeneous consolidation, multiple ill-defined nodules throughout the lung, or a focal ground-glass opacity
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They are often PET negative
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Pancoast's tumour (superior sulcus tumour)
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A Pancoast's tumour is an apical lung tumour which can extend into the chest wall and may resemble apical pleural thickening (and is commonly a squamous carcinoma) ▸ it can invade the subclavian vessels, brachial plexus (with pain radiating into the arm) and cervical sympathetic chain (leading to Horner's syndrome)
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MRI is the optimal modality for assessment but CT is used for assessing bony involvement
Lymph Node Staging
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Lung cancers normally spread sequentially to the ipsilateral hilar nodes, ipsilateral mediastinal nodes and then the contralateral mediastinal and supraclavicular nodes
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Skip metastases to the mediastinal nodes (in the absence of hilar nodes) can occur in
of patients
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Other causes of enlarged nodes: previous tuberculosis ▸ histoplasmosis ▸ pneumoconiosis ▸ sarcoidosis ▸ reactive hyperplasia to the tumour or an associated pneumonia
CXR
This is insensitive
CT/MRI
Generally nodes with a short-axis diameter of > 10 mm are considered enlarged (normal subcarinal and lower mediastinal nodes can be up to 10 mm – upper paratracheal nodes rarely exceed 7 mm) ▸ increased signal on STIR imaging in abnormal nodes ▸ however microscopic tumour involvement can be present in normal-sized nodes
EUS
This can assess nodal size and morphology, and guide fine needle aspiration of the aortopulmonary, subcarinal and posterior mediastinal nodes ▸ it has greater sensitivity and specificity than CT or PET in some series
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