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A lung nodule or pulmonary nodule is a relatively small focal density in the lung. A solitary pulmonary nodule ( SPN) or coin lesion, is a tumor in the lung smaller than three centimeters in diameter. A pulmonary micronodule has a diameter of less than three millimetres. There may also be multiple nodules.
One or more lung nodules can be an incidentaloma found in up to 0.2% of and around 1% of .
The nodule most commonly represents a benign tumor such as a granuloma or hamartoma, but in around 20% of cases it represents a malignant cancer, especially in elderly and tobacco smoking. Conversely, 10 to 20% of patients with lung cancer are diagnosed in this way. If the patient has a history of smoking or the nodule is growing, the possibility of cancer may need to be excluded through further radiological studies and interventions, possibly including surgical resection. The prognosis depends on the underlying condition.
The most important cause to exclude is any form of lung cancer, including rare forms such as primary pulmonary lymphoma, carcinoid tumor and a solitary metastasis to the lung (common unrecognised primary tumor sites are , or testicular cancer). Benign tumors in the lung include and .
The most common benign coin lesion is a granuloma (inflammatory nodule), for example due to tuberculosis or a Mycosis, such as Coccidioidomycosis. Other infectious causes include a lung abscess, pneumonia (including pneumocystis pneumonia) or rarely infection or worm infection (such as dirofilariasis or dog heartworm infestation). Lung nodules can also occur in , such as rheumatoid arthritis or granulomatosis with polyangiitis, or organizing pneumonia.
A solitary lung nodule can be found to be an arteriovenous malformation, a hematoma or an infarction zone. It may also be caused by bronchial atresia, sequestration, an inhaled foreign body or pleural plaque.
is defined as a pattern of air-filled bronchi on a background of airless lung, and may be seen in both benign and malignant nodules, but certain patterns thereof may help in risk stratification.
CT densitometry, measuring absolute attenuation on the Hounsfield scale, has low sensitivity and specificity and is not routinely employed, apart from helping to distinguish solid from ground glass lesions, and to confirm visible fatty areas or calcifications.
More frequent CT scans than what is recommended has not been shown to improve outcomes but will increase radiation exposure and the unnecessary health care can be expected to make the patient anxious and uncertain., which cites
In selected cases, nodules can also be sampled through the airways using bronchoscopy or through the chest wall using fine-needle aspiration (which can be done under CT guidance). Needle aspiration can only retrieve groups of cells for cytopathology and not a tissue cylinder or biopsy, precluding evaluation of the tissue architecture. Theoretically, this makes the diagnosis of benign conditions more difficult, although rates higher than 90% have been reported. Complications of the latter technique include hemorrhage into the lung and air leak in the pleural space between the lung and the chest wall (pneumothorax). However, not all these cases of pneumothorax need treatment with a chest tube.
Diagnosis
A diagnostic workup can include a variety of scans, blood tests, and biopsies.
Definition
Nodular density is used to distinguish larger lung tumors, smaller infiltrates or masses with other accompanying characteristics. An often used formal radiological definition is the following: a single lesion in the lung completely surrounded by functional lung tissue with a diameter less than 3 cm and without associated pneumonia, atelectasis (lung collapse) or lymphadenopathy (swollen lymph nodes).
CT scan
For incidentally detected nodules on CT scan, Fleischner Society guidelines are given in table below. For multiple nodes, management is based on the most suspicious node. These guidelines do not apply in lung cancer screening, in patients with immunosuppression, or in patients with known primary cancer.
+Solid nodules +Subsolid nodules
PET scan
If there is an intermediate risk of malignancy, further imaging with positron emission tomography (PET scan) is appropriate (if available). It can be done simultaneously as a CT scan in the form of PET-CT. Around 95% of patients with a malignant nodule will have an abnormal PET scan, while around 78% of patients with a benign nodule will look normal on PET (this is the test sensitivity and specificity). Thus, an abnormal PET scan will reliably pick up cancer, but several other types of nodules (inflammatory or infectious, for example) will also show up on a PET scan. If the nodule has a diameter of less than one centimeter, PET scans are often avoided because of an increased risk of false-negative results. Cancerous lesions usually have a high metabolism on PET, as demonstrated by their high uptake of FDG (a radioactive sugar)..]]
Other imaging
Other potential forms of medical imaging of pulmonary nodules include magnetic resonance imaging (MRI) or single photon emission computed tomography (SPECT).
Histopathology
For cases suspicious enough to proceed to biopsy, small biopsies can be obtained by fine needle aspiration or bronchoscopy are commonly used for diagnosis of lung nodules. CT guided Lung biopsy have also proven to be very helpful in the diagnosis of SPN.
Management
Excision
Where workup indicates a high risk of cancer, excision can be performed by thoracotomy or video-assisted thoracoscopic surgery, which can also confirm the diagnosis by histopathology.
See also
Footnotes
External links
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