Solitary pulmonary nodule

Chapter 17


Solitary pulmonary nodule


Khalid M. Amer










1


What is a solitary pulmonary nodule?

















A solitary pulmonary nodule (SPN) is a discrete radiological lesion less than 3cm in diameter, surrounded completely by normal lung parenchyma, in the absence of a pleural effusion, enlarged mediastinal lymph nodes or atelectasis.



This excludes multinodular disease and lesions with smaller satellite nodules.



By definition, an SPN is diagnosed on a chest X-ray (Figure 1) or computed tomography (CT) scan (Figure 2).



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Figure 1. A solitary pulmonary nodule (arrow) identified in the right lower zone on a chest radiograph.



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Figure 2. A solitary pulmonary nodule (arrow) identified in the left upper lobe on a thoracic CT scan with a background of fibrotic changes.












   


It is an incidental finding in 0.09-0.2% of all chest X-rays (150,000 chest X-rays or CTs/per annum in the United States).










2


What is the aetiology of an SPN?










 


Benign conditions














Congenital:

   















a)


arteriovenous malformations (AVM), hereditary haemorrhagic telangiectasia (Osler-Weber-Rendu syndrome);


b)


mucocoele within atretic bronchi.

   













Acquired:

   









a)


infection or abscess:
















i)


acute bacterial or viral infections;


ii)


bronchiolitis obliterans organising pneumonia (BOOP);


iii)


fungal, such as aspergillosis, histoplasmosis, coccidioidomycosis or actinomycosis;










b)


inflammatory:










i)


intrapulmonary enlarged lymph node or lymphoid tissue;










c)


granulomatous:
















i)


Mycobacterium tuberculosis;


ii)


histiocytoma (plasma cell granuloma or plasmacytoma) – which is the commonest benign cause in the USA;


iii)


collagen vascular disease, such as rheumatoid nodules (Figure 3), granulomatosis with polyangiitis or systemic lupus erythematosus (SLE);



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Figure 3. A rheumatoid granuloma (arrow) presenting as an SPN with speculated margins in a patient with rheumatoid arthritis.












   

iv)


autoimmune or idiopathic granulomas, such as sarcoidosis, amyloidosis and histiocytosis X;










d)


pseudotumours – round atelectasis caused by enfolded lung rotating on a fixed point of pleural disease, chronic scarring or asbestos-related plaque (Blesovsky syndrome, Figure 4). The benign nodule usually gives no symptoms;



images


Figure 4. A) CT scan demonstrating a 14mm left lower lobe SPN in the paravertebral gutter (red arrow), with round atelectasis (Blesovsky syndrome), related to pleural plaques (blue arrows). The vessels and bronchi converge upon and swirl around the mass (comet tail sign). Linear fibrous bands can be seen radiating from the mass into the lung parenchyma (crow’s feet sign). B) The associated PET scan was negative.















   

e)


ischaemic – lung infarction;


f)


developmental:



















i)


chondroid hamartoma (15%);


ii)


sclerosing haemangioma;


iii)


bronchogenic cyst;


iv)


lung sequestration.










 


Malignant conditions (approximately 50% of all SPN are malignant)














Primary lung carcinoma:

   


















a)


non-small cell carcinoma, such as adenocarcinoma, squamous cell carcinoma, adenosquamous carcinoma, large cell carcinoma (Figure 5) and primary pulmonary lymphoma;


b)


small cell carcinoma;


c)


carcinoid neuroendocrine pulmonary tumours.

   













Secondary lesions, metastasising from the colon (commonest site, accounting for 30-40% of all metastatic SPN), kidney (Figure 6), breast, prostate, thyroid, endometrium, skin melanomas and long bone sarcomas.

   


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Figure 5. A primary lung large cell carcinoma presenting as a cavitating and spiculated 15mm SPN (arrow) in the right upper lobe.



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Figure 6. A 6mm SPN (arrow) in the posterior aspect of the right lower lobe identified as a secondary lesion from a renal cell carcinoma.






















3


What are the important features in the clinical history of a patient with an SPN?



Symptom status – although an SPN is usually asymptomatic, any symptomatic SPN should be considered malignant until proven otherwise and should be investigated further.



Age – primary lung cancer is unlikely in non-smokers below the age of 40.



Smoking – increases the risk of primary lung cancer by 3.5 times and is proportional to the number of pack years. In ex-smokers, the risk of adenocarcinoma remains elevated for up to 30 years.



Haemoptysis – is highly suggestive of malignancy in a smoker, over 40 years of age. Benign causes for haemoptysis include pneumonia (Klebsiella), tuberculosis (TB), bronchiectasis, AVMs, lung sequestration and sclerosing haemangioma (Figure 7).



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Figure 7. Chest radiograph of a sclerosing haemangioma (arrow) in a non-smoking, 35-year-old female of Asian origin, presenting with a short history of cough and mild haemoptysis.




































   


Constitutional symptoms – including fever, night sweats, malaise, weight loss, arthralgia and myalgia, generally point to an inflammatory or infectious aetiology, such as lung abscesses, TB or vasculitis.



Drug history – especially of immunosuppressive medications.



Acquired immune deficiency status.



Travel history – including a recent exposure to TB or histoplasmosis.



Occupational risk factors – including exposure to asbestos or toxic fumes.



History of extrapulmonary malignancy – especially colon, breast, kidney, thyroid, uterus, prostate, seminoma, removed skin lesion (melanoma) and long bone sarcoma.



Previous mediastinal radiotherapy – which may result in post-radiation fibrosis and scar adenocarcinoma.



Paraneoplastic syndromes – including hyperpigmentation and Cushingoid features that may suggest lung carcinoid.



Previous radiology – increase in size over time is highly suggestive of malignancy, although a sclerosing haemangioma, may also increase in size (Figure 8).



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Figure 8. An enlarging solitary nodule (arrow) in the right upper lobe on chest radiograph.




























4


What are the important features in the clinical examination of a patient with an SPN?



Clubbing – which is found in lung cancer, chronic inflammatory conditions (such as bronchiectasis and lung abscess) and congenital AVMs.



Cyanosis, clubbing, skin naevi, lip telangiectases and a pulmonary murmur might suggest a pulmonary AVM or familial haemorrhagic telangiectasia (Osler-Weber-Rendu syndrome).



Heart murmur in a drug abuser might suggest tricuspid valve endocarditis, septic emboli and subsequent lung abscess formation.



Weight loss and cachexia may indicate underlying malignancy.



Epistaxis and skin lesions, such as a purpuric rash over the hands or legs, may suggest vasculitis.



Metastases from previous malignancy may be suggested by scars of a previous operation, such as mastectomy, or the presence of a leg prosthesis following long bone sarcoma.










5


What are the important radiological characteristics of an SPN?










 


Based on the Fleischner Society glossary of terms for thoracic imaging:





























Size – with lesions subdivided into those <8mm (which are managed by surveillance) and those between 8-30mm (which are managed by further investigation).



Shape – usually rounded (coin lesion) or oblong but can be lobulated.



Margins – smooth, irregular or spiculated (suggestive of cancer until proven otherwise).



Radiodensity – which can be radiodense (white) or radiolucent (grey or black) with high, low or indeterminate attenuation.



CT density – which is measured in Hounsfield Units, where the density of air is -1000 HU (black), fat -80 HU, water 0 HU, calcification >+165 HU and bone +700 HU.



Enhancement (with iodine contrast):

   















a)


benign diseases – which normally show an absence of enhancement (≤15 HU);


b)


malignant diseases – which usually ‘light up’ 5 minutes after injecting the contrast.

   
















Rim enhancement (or ring enhancement sign) – an area of decreased radiodensity surrounded by an enhanced ring is suggestive but not conclusive of a benign pathology. The enhancing rim is due to fibrotic inflammatory tissue surrounding a necrotic centre.



PET activity – which is referred to as ‘FDG avidity’ and measured in SUVmax (maximum standard uptake value). An SUV ≥2.5 is considered ‘hypermetabolic’ and indicative of malignancy (lesion ‘lights up’). It should be emphasised that the absence of FDG avidity does not mean the lesion is definitely benign.



Calcification – which is the only finding that reliably indicates a benign lesion.










6


What is a ground-glass opacity?























A ground-glass opacity (GGO) is defined as a hazy focal density, with ill-defined margins, but preserved bronchial and vascular markings.



The differential diagnosis of GGO ranges from inflammatory lesions to early primary lung cancer, with around 60% of GGOs being malignant.



Histologically, the ground-glass component typically corresponds to a lepidic pattern and the solid component to invasive patterns. Solid components usually arise from the airways. Bubble-like, cystic lucencies and bronchograms can appear within the GGO and are associated with well-differentiated adenocarcinoma.



GGOs are classified as:

   












a)


part-solid GGO (Figure 9A) – which is seen with mixed mucinous and non-mucinous adenocarcinoma;


b)


pure GGO (non-solid, Figure 9B) – which is seen in pre-invasive lesions, such as adenocarcinoma in situ (AIS) and atypical adenomatous hyperplasia (AAH).



images


Figure 9. A) Part-solid and B) pure ground-glass opacity (GGO) (arrow) in the right and left lower lobes, respectively (different patients).

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Feb 24, 2018 | Posted by in CARDIOLOGY | Comments Off on Solitary pulmonary nodule

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