A nodule is a spot in the lung. Solitary pulmonary nodule means that there is only one in the lung. A nodule is a common finding on imaging of the chest. Nodules are spots that stand out from the dark lung and have a white appearance to the radiologist. A nodule can be any size up to about 3 cm. We call it a mass when it is bigger then 3 cm.
Lung Nodule Causes
Lung nodules can have many causes, the most concerning of which is cancer. The radiologist can sometimes suggest a specific diagnosis based on the appearance. If the nodule is calcified, or real white and dense, a granuloma can be diagnosed which is benign. If the nodule is shaggy or has irregular edges, it becomes more concerning for cancer, particularly in someone who is a smoker. Nodules can represent lung infection or inflammation. Some nodules may simply be normal overlapping structures such as blood vessels or ribs on a chest x-ray.
Calcified Vs Non-Calcified Lung Nodule
A chest CT is often the next test that is suggested to take a closer look at the appearance of a lung nodule. Sometimes calcifications may be better appreciated and diagnosis of benign granuloma is made. Other times the radiologist may see fat and call it a benign tumor called a hamartoma. Other times a vascular malformation can be diagnosed if there are blood vessels feeding and draining it. We can not identify the diagnosis for most non calcified nodules.
Small Lung Nodule
A small lung nodule is one under 8 millimeters. The small lung nodules are often followed according to Fleischner Society guidelines that are established. These can be repeat scans anywhere between 3-12 months. This depends on the appearance and size.
Those nodules greater then 8 millimeters need more aggresive attention. These can be reevaluated with a follow up CT in 3 months, a PET scan or biopsy. The exact workup will depend on the appearance, size, and risk factors.
When does lung nodule need a biopsy?
The Fleischner society offers biopsy as an option for nodules greater then 8 millimeters. Often factors like the size, appearance, PET results, risk factors of the patient will influence the decision.
When do you need follow-up for a lung nodule?
Sometimes it remains unclear what the diagnosis is and a follow up is recommended. If the nodule is under 8 millimeters, than follow up imaging is needed. There are well accepted published guidelines to follow from the Fleischner society. If the nodule is bigger than 8 millimeters, then the radiologist may recommend another test such as PET scan or biopsy.
Are lung nodules cancerous?
Lung nodules can range from benign to cancerous. The smaller the size, especially under 1 cm, the more likely to be benign. Other features such as if it is smooth or irregular, your smoking history, and other features the radiologist sees will determine the next best step.
Patients who are younger then 35 or are immunocompromised are more likely to have infectious nodules. Patients who have cancer as a diagnosis are more likely for the nodule to be related to cancer.
When should you be worried about a solitary pulmonary nodule?
The bigger the size the more likely the nodule is cancerous. Those nodules greater then 8 mm need more aggresive follow up and workup.
Those nodules that grow are more concerning. Factors such as older age, history of smoking or other inhaled carcinogens, lung fibrosis or scarring, family history, irregular or spiculated edges, and upper lung location also makes a nodule more suspicious.
Solitary Pulmonary Nodule: Summary
Solitary pulmonary nodules are commonly found on imaging of the chest. The workup depends on the size and appearance of the nodule. There are imaging features and patient specific factors that make a nodule more suspicious for cancer. Further follow up of smaller nodules is based on established guidelines. Larger nodules over 8 mm my need more aggresive follow up and workup as the risk for cancer is higher.