So in this lecture, we'll be discussing pulmonary nodules.
We'll go over how you can determine whether a nodule is benign
or malignant and we'll go over some of the follow-up
that may be indicated if you do see a nodule.
So, let's start off with this case.
Let's take a look at the findings and keep this in mind
as we go through the lecture.
The finding is actually located in the left upper lung right here,
we'll go back to this case at the very end.
So the key question when you see a pulmonary nodule is,
is it benign or is it malignant?
Because obviously, there's a very different follow-up indicated
depending on whether it's benign or malignant.
So, in general, benign nodules tend to have very smooth margins
while malignant nodules tend to be a little bit more spiculated.
Benign nodules are usually smaller,
they're usually about less than four millimeters in size
while malignant nodules are usually much bigger,
greater than about five centimeters in size.
Benign nodules tend to have calcifications,
malignant nodules tend to increase in size a lot more
than benign nodules would. And an example of a benign nodule
is usually a granuloma or a hamartoma,
those are the two most common that are seen within the lung.
In terms of malignancy,
you can have bronchogenic carcinoma or metastasis.
So when would you call it a nodule versus when would you call it a mass?
Nodules are generally less than about three centimeters in size,
masses are greater than or equal to about three centimeters in size
so that's really the size criteria that you use
when you're describing a nodule or a mass within the lung.
So, what kind of work-up does the nodule need?
If it's less than about a centimeter,
a radiograph is really not reliable in terms of visualizing it
so you have to go further and usually the next step would be a CT scan.
Most nodules are actually found incidentally on a radiograph
and if you do see an incidental nodule,
you also want to recommend a CT scan
to make sure that there aren't other nodules that you may be missing.
So the CT scan is the first step for a full evaluation of the lungs.
Follow-up is actually based on Fleishcner Society criteria,
this is a group of international chest radiologists
that have come up with a general criteria
for follow-up of pulmonary nodules and we'll go over that.
So this is the chart that they use.
If the nodule is less than or equal to about four millimeters in size.
In a high-risk patient, you would wanna do a chest CT in about a year
and then no further imaging is needed if their nodule remains unchanged.
In a low-risk patient, there's really no follow-up that's indicated
in such a small sized nodule.
If it's anywhere between four and six millimeters in size,
then in a high-risk patient, you would wanna do a chest CT
in somewhere between six and 12 months
and then a repeat in 18 to 24 months
to ensure that this nodule stays stable.
In a low risk patient you would just do a follow-up in a year
and then no further imaging if it remains unchanged.
A little bit larger, anywhere between six and eight millimeters,
you would wanna do the chest CT a little bit more frequently.
So in a high risk patient, you would start at three to six months
and then a couple of follow-ups at nine to 12 months,
and then again at 24 months to again ensure
that it stays stable for a period of about two years.
In a low-risk patient of a nodule this size,
you would wanna start off with a chest CT at about six to 12 months
and then do a repeat again in about 18 to 24 months
to ensure that it's stable.
If a nodule is greater than eight millimeters,
then you would wanna consider doing a chest CT again at three, nine,
and 24 months or you could possibly go on to a PET
and/or a biopsy depending on how high-risk the patient is.
In a low-risk patient, you would really wanna do the same thing,
so a follow-up chest CT or again, a PET and/or a biopsy
depending on what the nodule looks like
and if there are any risk factors associated with the patient.
So, you can keep this table with you.
This is a great way to kind of take a look at the table
whenever you do have a nodule that you see on a chest CT.
So, what exactly is a PET CT?
It stands for Positron Emission Tomography and it's a CT scan,
so it's a combination of two different studies.
It's a type of nuclear medicine examination
which uses a radiotracer usually called FDG or fludeoxyglucose
which concentrates in areas of high glucose uptake.
It's paired with a CT scan to help delineate the anatomy
and it allows for detection of malignancy and metastatic disease.
The lesion threshold though is about seven millimeters.
So if a lesion is smaller than seven millimeters,
it's very unlikely to be seen on the PET.
For lesions that are greater than seven millimeters,
a PET CT is a great alternative to taking a look at
whether the lesion is malignant or benign.