What does a pulmonary nodule look like?
- A pulmonary nodule is basically a small focus of tissue in the lung. It is usually round but can often be oval, irregular, or speculated. Sometimes is can be calcified or have fat density.
- By definition a nodule is less than 3cm in size. If the lesion is greater than 3cm, it may be the exact same tissue etiology, but it is now called a mass.
What could it mean?
- Fat density in a nodule is considered benign.
- If calcifications are seen within a pulmonary nodule it is almost always benign as well.
- Calcifications are associated with prior or chronic inflammation/infection. In this scenario, the nodule is the tissue that is left over after your immune system has taken care of the problem. It is kind of like a scar.
- These “scars” do not always calcify and a non-calcified nodule can be more difficult to evaluate. None the less, a noncalcified-nodule can still represent the benign residue of a prior infection, but it is hard to tell for sure. So that is usually the major question; is the nodule cancer or not?
- The good news is that the vast majority of lung nodules are benign.
- The bad news is, if the nodule is not calcified or does not have fat, it can be difficult to impossible to tell on one CT scan if a nodule is cancer or not.
- Because cancers grow and scars generally do not, a follow-up scan can help. Scans at different times provide a reference point to evaluate if it increases in size over time. Some types of cancers grow very slow and therefore a long follow-up may be necessary to feel comfortable that the nodule is benign.
- Other factors play a role in the likelihood that a nodule is a cancer or not. The chances that a nodule is malignant increases with nodule size. Some other common factors that increase the likelihood that a nodule could be cancer is; patient age, history of other cancers, smoking history and history of other carcinogen exposure.
How often do you re-scan with CT and for how long?
- This is a major issue that is debated by many.
- In the last decade several articles have been published in major peer reviewed medical journals to try to establish a safe and rational approach to the management of this common issue. Most recently, in 2005 a consensus guideline was created and adopted by the major medical society on chest imaging (the Fleischner Society). Their follow-up algorithm is very helpful but remains general and many other individual factors will dictate management. The article is online:
This algorithm was used when I was at MGH. However, things in medicine often change with medical advances and it is possible that it has been updated since.