0:01

Now comes the point in terms of when

0:03

do you call a lymph node positive?

0:05

Now, when you talk about the mesorectal

0:09

lymph nodes, there are two things you use.

0:11

One is size and the other one you use morphology.

0:16

When this node, mesorectal node in short

0:19

axis measures more than nine millimeters.

0:22

So as we measured this one,

0:26

9.1 millimeters, so it's more than nine.

0:27

If it is more than nine millimeters,

0:30

you do not have to look at morphology.

0:32

You call this node positive.

0:35

If it is between five and eight millimeters,

0:37

so let me find you, find us an example.

0:41

Okay.

0:41

So we measure this one now.

0:45

So this is less than nine millimeters, but

0:49

it is between five and eight millimeters.

0:52

So if it is between five and eight, then

0:55

you not only look at size, but you also

0:58

need to look at changes in morphology.

1:00

And what are the three things in

1:01

the morphology thing you look for?

1:03

Is the node round in shape?

1:05

Yes or no?

1:07

Does the node have heterogeneous signal?

1:10

Yes or no?

1:11

And does the node have irregular margins?

1:14

And all these three morphologic features

1:17

are seen on T2-weighted sequences.

1:20

So we saw this node was between five and eight.

1:23

Is the node rounded?

1:24

Yes.

1:25

Does it have irregular margins?

1:28

I think the answer is no because you

1:29

can fairly see well-demarcated margins.

1:33

Does it have heterogeneous signal?

1:36

And again, you know, that's sort of a point of

1:38

debate. I mean, there are subtle dark areas, but

1:41

I would not necessarily call this heterogeneous.

1:43

So for a node between five and eight millimeters,

1:47

it has to meet two of those three criteria for

1:51

you to call it positive, which, you know, this

1:53

one meets one but doesn't meet the other two.

1:55

So it will not fall into the category of being,

1:59

whereas if you look at this one in contradiction

2:02

and if I'm going to measure this right here.

2:05

So this is also between five and eight

2:07

millimeters, but compared to this one, it's not

2:10

rounded, but it does have irregular margins and

2:13

it does have heterogeneous signal intensity.

2:15

Okay.

2:15

So this would fit the bill for it being malignant.

2:18

And if it is less than five millimeters,

2:21

it needs to meet all three criteria,

2:23

which means it has to be round, it has to

2:25

be heterogeneous, it has to be ill-defined.

2:28

So that's for the mesorectal lymph nodes.

2:30

I hope that's clear.

2:31

You know, you look at size

2:32

greater than nine millimeters.

2:35

That's all you use.

2:36

If it is between five and eight millimeters,

2:38

you look for two of the three morphologic

2:41

criteria, and the morphologic criteria are

2:43

node being rounded, node being irregular, and

2:46

node being heterogeneous in signal intensity.

2:49

And if the node is less than five millimeters, it

2:51

needs to have all three in terms of morphology.

2:54

It has to be round, it has to be

2:56

heterogeneous, it has to be irregular.

2:58

Irregular or ill-defined in outline.

3:00

Now, what about the extra

3:03

mesorectal regional lymph nodes?

3:05

The extra mesorectal lymph nodes, they do

3:07

not follow the criteria I just mentioned.

3:10

For that, you just use the

3:11

short axis of seven millimeters.

3:13

And that has been proven in literature.

3:15

It's, you know, there was a 2019 paper that

3:19

came out of Japan where they do a fair amount

3:22

of dissections of these pelvic sidewall nodes.

3:25

And what they found was nodes that were

3:28

positive were more than seven millimeters.

3:30

So unlike the mesorectal where you look at

3:33

nine, five to eight, and less than five in

3:36

the extra mesorectal regional nodes, you use

3:39

seven millimeters in short axis as the cutoff.

3:44

And then the last point that I would like to mention

3:46

is if you have a node which is seen with a mucinous

3:49

primary and the node is mucinous, which is seen

3:51

with a mucinous primary and the node is mucinous.

3:53

Then none of the, you don't apply any size

3:55

criteria, you just call it positive and,

3:57

you know, I'll show you an example of that.

4:00

So using that criteria, you can see that there

4:02

are multiple positive nodes, and, uh, here is one.

4:07

This is the outline of the mesorectal fascia.

4:08

This is outside, so this is extra mesorectal.

4:11

It's along the internal iliac.

4:13

So this is an internal iliac node right here.

4:15

And as I mentioned for the extra mesorectal lymph

4:19

nodes, you use seven millimeters in short axis.

4:22

So if I measure the short axis, this is

4:25

clearly more than seven millimeters and

4:28

you would definitely call this positive.

4:30

So this patient not only has regional mesorectal

4:34

nodes that are positive, but also has extra mesorectal

4:37

lymph nodes, an internal iliac node that is positive.

4:41

So that is one point.