Lung cancer. The Solitary Pulmonary Nodule

CONTENTS:

3.2 The ‘Solitary Pulmonary Nodule’ (SPN) or ‘Coin Lesion’
3.2.1 The Incidence of Solitary Pulmonary Nodules (SPNs)
3.2.2 Why Are Smokers More Likely to Have Lung Nodules?
3.2.3 The Causes of Solitary Pulmonary Nodule (SPN)
3.2.4 How Often Are Solitary Pulmonary Nodules Cancerous?

Forward to 3B Models for predicting Malignancy in a Solitary Pulmonary Nodule Back to 3A Benign Conditions of the Lung: Introduction

Looks like we’re going to be getting very familiar with pulmonary nodules.

Yes, I hope there’s some pictures of them.

Nothing wrong with a good noduling.

3.2 The ‘Solitary Pulmonary Nodule’ (SPN) or ‘Coin Lesion’

Solitary pulmonary nodules (SPN) are radiographically-detected lung tissue densities, that are smaller than 3 cm (30 mm). They are not associated with other lung or mediastinal disease. A tumor that is larger than 3 cm (30 mm) is considered to be a ‘lung mass‘ and these are usually malignant.

The clinical assessment and diagnosis of SPNs depends on host factors and the radiographic morphologic features. Further investigations may be required to determine whether the lung nodule is benign or malignant.

The factors that may be suggestive of malignancy include age, smoking history, and any previous history of having had cancer. Radiographic factors that may support the likelihood of lung cancer as a cause of the nodule include size, calcifications, irregular pattern or ‘spiculated’ borders, and the growth rate.

Figure 3.5 The Solitary Pulmonary Nodule (SPN).

A. CT image of a single lung nodule, with a ‘popcorn’ appearance;
it is well-circumscribed. B. Excision specimen of a pulmonary
hamartoma showing the spaces containing fat or lined by epithelial cells.
C. Photomicrograph of the histology of a benign hamartoma,
contains cartilage (c), fat (f), and epithelium (e).

3.2.1 The Incidence of Solitary Pulmonary Nodules (SPNs)

An imaging diagnosis of solitary pulmonary nodule (SPN) is a very common clinical problem. Lung cancer screening for smokers who are at high risk for lung cancer has shown a prevalence of SPNs to be as high as 50 %. In the U.S., 150,000 new solitary pulmonary nodules are detected each year.

3.2.2 Why Are Smokers More Likely to Have Lung Nodules?

In addition to their increased risk of developing lung cancers, cigarette smokers will have a number of changes to their lungs over time that will lead to focal or diffuse abnormalities. The following lung diseases are also seen in solitary pulmonary nodule smokers:

Chronic obstructive pulmonary disease (COPD) that includes chronic bronchitis and emphysema.
Lung carcinoma in-situ, atypical hyperplasias and lung cancer.
Interstitial lung disease (ILD)
Respiratory bronchiolitis interstitial lung disease (RBILD
Desquamative interstitial pneumonitis (DIP)
Usual interstitial pneumonia/idiopathic pulmonary fibrosis (UIP / IPF)
Pulmonary Langerhans’ cell histiocytosis (histiocytosis-X).

My doctor said that if you had X-Ray vision and you could see your lungs, you’d never smoke again.

Too right! If I had X-Ray vision I’d be too busy looking through girl’s skirts.

Oh Hector! Really?

3.2.3 Causes of Solitary Pulmonary Nodule (SPN)

If the imaging and clinical features support a benign cause of the lung nodule, then the differential diagnosis includes infection, an inflammatory lesion, a congenital or developmental abnormality, a vascular malformation, or a hamartoma. The most common benign SPNs are hamartomas and granulomas.

BENIGN (Non-Cancer) (50%)

Congenital

Bronchogenic cyst
Pulmonary sequestration

Tumor

hamartoma
chondroma (hamartoma)
sclerosing hemangioma
neural tumor (neurofibroma, schwannoma)
arteriovenous malformation

Infection

infectious granulomatous disease (mycobacteria [tuberculosis]. fungi [Aspergillus, Cryptococcus, Histoplasma], bacteria [Nocardia, Actinomyces], virus infection [measles]).
abscess
septic embolus

Non-Infectious

Granulomatous disease (sarcoidosis, Wegener’s granulomatosis)
scar
amyloid
sub-pleural lymph node
rheumatoid arthritis
pulmonary infarct

MALIGNANT (50%)

Primary

lung carcinoma (cancer)
non small cell lung cancer (NSCLC): – adenocarcinoma, squamous cell carcinoma
small cell lung cancer
primary lung lymphoma
primary lung carcinoid

Metastatic (Secondary)

Breast, colon, prostate, renal cell, melanoma, osteosarcoma, testicular cancer.

A man goes into a library and asks for a book on ‘probability.’ The librarian says, ‘It might be on the shelf over there.’

3.2.4 How Often Are Solitary Pulmonary Nodules Cancerous?

In 1993, Lillington and colleagues found that cancer was present in solitary pulmonary nodules (SPN) in 50% of steven-shad cases. They also showed that the 5-year cure rate after resection of a malignant nodule was 50 %. These investigators also noted that if there was no change in a lung nodule during a 2-year period, this suggested a benign cause. They advised a ‘watch and wait’ approach to be followed when a lung nodule has not changed within 2 years. They also observed that the presence of certain patterns of calcification within the nodule was a benign feature, but that multiple pulmonary nodules are usually due to metastatic spread from an extra-pulmonary primary tumor.

In 1993, Midthun and colleagues, reported on the diagnostic challenge for an imaging diagnosis of a single lung nodule. They reported that the likelihood of a malignant tumor correlates with the age of the patient, the size of the nodule, a history of a prior malignancy, and a history of smoking.

In 2005, Davies and colleagues investigated the findings from the histopathology examination of lung resection lung-ca-sophie's-mum specimens of solitary pulmonary nodules (SPNs), < 30 mm in diameter and a city-dwelling population. An analysis of 150 patients (80 men), who had a mean age at resection of 64.7 years, and a mean nodule diameter of 17.6 mm resulted in 87 open lobectomies, 9 bilobectomies, 51 wedge excisions and one pneumonectomy. Lung cancer was diagnosed in 115 patients (77.7%); 97 (65.5%) were primary lung cancer and 18 (12.2%) had metastatic cancer deposits; 30 (20.3%) were benign. There was no significant correlation between nodule size and malignancy risk.

So size of the nodule seems to be quite important here.

Size is important everywhere Gretchen.

I was talking about the Solitary Pulmonary Nodule or ‘the Lonely Lump’!

The key clinical factors for Solitary Pulmonary Nodule

In summary, the key clinical and imaging factors that may be associated with a benign cause for a SPN are:

Size – measured as the maximum diameter of the lung nodule. The estimated risk of cancer, according to nodule size is:

Nodules <5 mm: <1 %
Nodules 5 to 9 mm: 2 to 6 %
Nodules 8 to 20 mm: 18 %
Nodules >20 mm: >50 %

Location – Malignant nodules may be found anywhere in the lung, but those located in the upper lobe are more likely to be malignant.

Nodule Attenuation – solid or sub-solid (pure and part-solid). Part-solid (‘ground glass’ appearance) nodules have a higher chance of being malignant, including atypical adenomatous hyperplasia (AAH), adenocarcinoma in situ (AIS), and minimally invasive adenocarcinoma (MIA) (see Section 4).

Nodule Growth – CT is used as a diagnostic and management tool to assess nodule growth and stability. A solid nodule that has been stable for two years and a sub-solid nodule that is stable for three years are likely to be benign, and immediate tissue biopsy can be avoided. The ‘volume doubling time’ (VDT) of cancers have been helpful in predicting the probability of malignancy.

Nodule Border – The risk of malignancy is lower in SPNs with smooth borders (20 %) and higher in those with irregular borders: scalloped (60 %) and spiculated (90 %).

Calcification – Asymmetric calcification or ‘eccentric’ calcification, may raise concern for malignancy; ‘popcorn’, laminated (concentric), central, and diffuse patterns of calcification may suggest a benign nodule. Patterns of calcification are suggestive but not diagnostic for cause of the nodule.

Imaging for Solitary Pulmonary Nodule

Functional imaging — Lung cancers are more metabolically active than benign lesions, so functional imaging may be used to help distinguish benign from malignant nodules. Positron emission tomography (PET), dynamic contrast-enhanced CT scan, dynamic magnetic resonance imaging (MRI), and dynamic single photon emission CT scan may be used. PET is the preferred modality because it is more widely available.

Typically, SPNs that are >30 mm are surgically resected because they have such a high probability of malignancy and so the benefit of resection outweighs the risk of surgery.

SPNs ≤ 8 mm (without growth) are followed by serial CT scan; these nodules have a low probability of being malignant, so the benefits of resection may not justify the risk surgical resection.

I’d like to defend a penguin in court just to say, “Your Honour, my client is clearly not a flight risk.”

References:

Lillington GA, Caskey CI. (1993). Evaluation and management of solitary and multiple pulmonary nodules. Clin Chest Med. 14(1), 111. (Retrieved 5^th Feb 2015): http://www.ncbi.nlm.nih.gov/pubmed?term=8462244

Midthun DE, Swensen SJ, Jett JR. (1993). Approach to the solitary pulmonary nodule. Mayo Clin Proc. 68(4), 378. (Retrieved 5^th Feb 2015): http://www.ncbi.nlm.nih.gov/pubmed?term=8455399

More references for this section are on this page.

Patient Information:

Web MD Benign Lung Tumors and Nodules (Retrieved 28^th March 2015):http://www.webmd.com/lung/benign-lung-tumors-and-nodules

Medscape Solitary Pulmonary Nodule (Retrieved 28^th March 2015): http://emedicine.medscape.com/article/2139920-overview

More patient information for this section is on this page .

Forward to 3B Models for predicting Malignancy in a Solitary Pulmonary Nodule Back to 3A Benign Conditions of the Lung: Introduction