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This video we are going

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to briefly discuss FDG PET CT in lymphoma staging.

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And in a subsequent video we'll discuss follow up.

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We're gonna give some background content for you to refresh,

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um, some um, aspects of lymphoma.

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Its classification based on either Hodgkin's

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or non-Hodgkin's lymphoma or low grade

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and high grade, as well as some clinical features.

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And then we are going to discuss the initial staging

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classification, both clinically

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and also how we do it with PET ct.

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So just briefly, there's many types of lymphoma

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and commonly they are divided into either Hodgkin's

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cell type or non-Hodgkin's uh, lymphoma.

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Within the non-Hodgkin's lymphoma,

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we can find a B cell which are the most common

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and less common T-cell lymphoma.

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I have listed many of them under each cell type

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and I have added an asterisk next to those

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that are considered low grade lymphomas.

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The others are considered high grade lymphomas.

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The reason why this is important is

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because the appearance with FDG PET will differ

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depending on the grade.

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High grade lymphomas will be more aggressive,

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the cells are poorly differentiated

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or undifferentiated fast growing.

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And so we will see a higher degree of tracer uptake

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while low grade lymphomas are of indolent nature.

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And so the FDG uptake will be lower.

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This can transform to high grade lymphoma.

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So this is something to always keep in mind when we're

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reading cases and we'll discuss that as we go

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through examples.

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So for initial evaluation of lymphoma,

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clinicians will biopsy the adenopathy of concern

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and will run different studies including

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pathologic morphology, immunohistochemistry

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and flow cytometry.

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And sometimes uh, farther molecular studies are needed.

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Sometimes the samples are inadequate and

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therefore they would move to excisional biopsy

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in which they would remove the entire lymph node.

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The classification clinically will follow the

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Lugano classification,

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which is essentially a modernized an arbor

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that we all studied back in the day

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and essentially is the same in which you divide the

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adenopathy into

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how many different nodal groups are involved if they are

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ipsilateral or contralateral, and if they are above

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or below the diaphragm, as well

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as if there is extra no analysis.

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It has been reported that FDG PET TT can lead

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to a change in a stage in 10

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to 30% of patients.

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And more often than not we upstage rather than under stage.

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So our role as imagers is crucial in lymphoma.

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Just a note, when

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to define bulky disease is in Hodgkin lymphoma,

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particularly if the disease

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or no mass is greater than 10 centimeters

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or occupies a third of the thoracic diameter on the ct.

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For instance, in follicular lymphoma,

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we would use a six centimeter cutoff

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and in diffuse large B-cell lymphoma,

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we would also use a 10 centimeter cutoff.

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And these are things that if you see in the report

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would be worth mentioning.

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So the clinician knows how to better manage this patient.

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So how can we help?

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So first we have to determine the extent

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of the metabolic disease.

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We also can identify areas that are occult

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to the clinician or occult on another morphologic study.

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We can also identify areas of biopsy

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and we would be selecting those based on accessibility,

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but also those that have a higher degree of uptake

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to be representative of the most aggressive disease.

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We can also look at bone marrow involvement

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in a single study.

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And then obviously we also have a CT portion, right?

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So we can discuss morphologic changes,

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but these are limited to size

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and so obviously the CT alone would be limited.

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Adding the metabolic information

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is crucial in these patients.

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So how to approach a report for a baseline PET ct.

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What I do is I essentially classify

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my impression, but when I read the study, I want to answer

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the question of how many categories are involved.

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Is there not a disease? Where is it?

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So I'm gonna say if novelis is above and

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or below the diaphragm, essentially

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how many novel groups are.

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I will address that in the body of my report.

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I don't have to give measurements

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for every single lymph node that is involved,

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but I will mention those

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that are representative in different areas.

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For instance, above the diaphragm

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or below the diaphragm, I'm going

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to mention if there is extra nodal disease.

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And then whenever I discuss the degree of uptake, I'm going

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to compare it to blood pool or mediastinum

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and liver 'cause those are our

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standard of uptake. That

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Would give us an idea of aggressiveness of disease.

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If there is no diagnosis yet, I will say that if the tissue

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is needed, consider this area or this other area.

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This is very helpful for the clinicians

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and it also helps our colleagues when they receive a request

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for a biopsy, if we can tell them

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where we think would be a representative

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sample, it's better for them.

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They can focus more on the approach.