0:01

Now comes the next point is what

0:03

constitutes a tumor deposit.

0:06

And this is an important distinction to be made, uh,

0:09

between what is a lymph node and what is not a node.

0:12

So if you ask a pathologist what constitutes

0:16

a tumor deposit, they will tell you that

0:18

a tumor deposit is an entity defined in, within

0:23

the specimen that when they look at it, it is

0:27

remote from the primary tumor, which means

0:30

you know, if the primary tumor is here,

0:32

it's somewhere in the mesorectal fat and has no nodal

0:36

or no vessel component that can be identified.

0:39

So that's what they refer to as a tumor deposit.

0:43

How do we translate that into MR?

0:45

So on MR, the classic definition has been tumor

0:49

deposits are those areas that are seen in the

0:53

mesorectal fat that typically have vessels

0:56

that lead to them and lead away from them.

0:59

In other words, think about it as if I was

1:04

to kind of diagrammatically, you know, describe

1:07

it, think about it as a vessel as such and what

1:12

you see is a tumor deposit within the

1:18

so the proximal part of the vessel is normal.

1:19

The distal part of the vessel is normal.

1:21

There is tumor spread along the vessel and it

1:24

has lodged somewhere in the middle of the vessel.

1:26

So what you see is a vessel

1:27

going into a vessel going out.

1:30

So it is an interruption of the course of a

1:32

vessel, whereas a lymph node does not have this.

1:35

So that's typically what you would call a tumor

1:37

deposit, and you have to be vigilant when you are

1:42

looking at patients like this where you

1:45

have multiple lymph nodes, so you're not, uh, you know,

1:49

missing out on a tumor deposit.

1:54

So, if I can, if I can show you, here is a

1:58

vessel that is emanating from the anterior wall

2:00

of, you can see there is a flow void that is

2:02

emanating from the, um, the part of the cancer.

2:07

And as I follow this, you will see that there is this

2:12

area which clearly falls in the path

2:15

of the vessel, and you can cross-confirm that on

2:17

the other view. Here it is on the sagittal as well.

2:21

You can see there is this vessel that is leading

2:24

beyond it, and it's this deposit which has a vessel

2:27

coming to it and then a vessel going away. So this is what

2:29

you would refer to as a tumor deposit, and so that's

2:33

something again important to keep in mind and put

2:35

in the report because the prognostic implications

2:38

of these tumor deposits are similar to that of

2:40

a lymph node. So it's this area, right?

2:44

As I'm crossing, it's this lesion posteriorly

2:46

where you can clearly see a vessel going

2:48

to it and then away. These are the

2:50

vessels going away from that tumor deposit.

2:53

So keep in mind that, you know,

2:55

that's what a tumor deposit means.

2:57

Now, here is also a good example of a lesion where we

3:01

can see that there is, you know, it's extending beyond.

3:03

And we looked at on the earlier

3:04

images, we measured the distance.

3:07

Uh, from the wall, but, uh, if you look

3:09

closely here, it's close to 15 millimeters,

3:14

uh, extension beyond, and it is touching

3:16

the, um, mesorectal fascia right here.

3:19

So there is involvement of the mesorectal fascia.

3:22

There is presence of tumor deposits.

3:24

There are lymph nodes, and this is a T3 disease

3:26

with T3D because it is 15 millimeters extension

3:29

into the, um, and so early on we had measured the,

3:33

the, uh, smaller component here.

3:35

Here we are measuring the larger component now.

3:38

And so again, you have to kind of, that's why you have

3:41

to bring it forward like this, keep on looking at

3:43

all the images, and then filling in the template.

3:47

And so that's sort of in a nutshell, um, about this

3:51

case. The take-home messages here are, you know, when

3:53

you do have a T3 disease with extension beyond, this

3:56

is a T3 with involvement of the mesorectal fascia.

4:00

What constitutes regional from non-regional nodes?

4:03

What are the criteria that we use for distinguishing

4:06

benign from malignant within the mesorectal space?

4:09

In the pelvic sidewall, uh, regional lymph nodes.

4:12

What do you call non-regional nodes?

4:13

So if you had positive nodes in the

4:15

external iliac chain, that would be

4:16

non-regional or distant metastases.

4:19

And then what constitutes a tumor deposit?

4:22

It's basically, uh, soft tissue nodules

4:25

where the vessel course is interrupted.

4:27

And again, the implications of having,

4:30

uh, tumor deposits is akin to that of having EMVI,

4:34

which typically means there is a bad prognosis.