0:01

Adenoid cystic carcinoma is not the most common

0:04

tumor of the parotid gland or the most common

0:08

malignancy of the parotid gland, that's

0:09

mucoepidermoid carcinoma. However,

0:12

everywhere else, the submandibular gland,

0:14

the sublingual gland, and the minor salivary glands,

0:17

adenoid cystic carcinoma is the most

0:19

common histology for malignancy.

0:23

Let's look at this case.

0:24

Here, we have a patient who had epistaxis

0:27

on the left side. As we scroll up,

0:30

we see the opacified

0:33

left maxillary antrum and a mass which is present in

0:37

the nasal cavity growing into the medial

0:40

wall of the left maxillary antrum.

0:43

As you follow this lesion posteriorly,

0:45

you can see it crosses the midline and

0:47

infiltrates the ethmoid air cells.

0:50

It continues more posteriorly and goes

0:52

into the sphenoid sinus. Now,

0:55

how much of this is tumor and how

0:57

much of this is obstructed

1:00

secretions is usually helped out by your

1:02

T2-weighted scan. In this case,

1:04

we're using CISS imaging, and as you can see,

1:07

the tumor has this darker signal intensity to it, but

1:11

the secretions are brighter in signal intensity.

1:14

So we can infer that the posterior wall of the tumor

1:19

is sitting within the sphenoid sinus, but the

1:23

posteriormost portion of the sphenoid sinus is clear.

1:27

This could be better demonstrated on the

1:29

post-gadolinium enhanced scan where tumor enhances

1:33

but obstructed secretions do not.

1:36

So let me use my pen and sort of outline this

1:40

for you. This is the border of the tumor.

1:48

These are obstructed secretions which you

1:51

can see in this sphenoid sinus.

1:53

Now,

1:54

because of the different protein concentration

1:57

of the secretions, you may see

2:00

some heterogeneity to those secretions on the

2:04

CISS image.

2:06

If you're considering adenoid cystic carcinoma, you

2:09

want to make sure you look at the tributaries

2:12

of the pterygopalatine fossa.

2:15

So let's scroll here and see what we can find.

2:19

Well, where is the pterygopalatine fossa?

2:22

The pterygopalatine fossa is that tissue which is

2:25

just in front of the pterygoid plates at the skull

2:29

base, and it normally has high signal intensity fat

2:33

and maybe a pterygopalatine ganglion that looks a

2:37

little bit like this, a darker signal intensity

2:39

structure within the pterygopalatine fat.

2:43

If we look on the left side,

2:47

we see tissue which is intermediate in signal

2:51

intensity that is infiltrating the pterygopalatine

2:55

fossa. So this is, I think, better seen on the

3:00

post-gadolinium enhanced scan where you can see that

3:03

there is this enhancing tissue that should

3:05

not be there on the post-gadolinium

3:08

T1-weighted imaging.

3:11

That leads us to have the concern that this may

3:15

represent tumor infiltration of the pterygopalatine

3:19

fossa. So let me use the pen one more time.

3:23

All right? So pterygoid plate, pterygoid plate,

3:26

pterygopalatine fossa, pterygoid plate,

3:29

pterygoid plate.

3:30

Small enhancing tissue there that is worrisome.

3:37

If we follow that upwards,

3:41

we see again this small amount of tissue that is

3:44

enhancing there that does not appear

3:46

on the contralateral side.

3:48

And this is very concerning because we have the

3:52

tissue outside the posterior wall

3:54

of the maxillary antrum. Here is

3:55

the posterior wall of the maxillary antrum.

3:57

Nothing is enhancing here of concern.

4:00

But here we have tissue which is enhancing.

4:04

And where is it going?

4:05

It's going into the orbit.

4:08

This is one of the outflows of the pterygopalatine

4:12

fossa is the inferior orbital fissure.

4:15

Again,

4:16

what I'm concerned with is this tissue

4:18

here which is entering the orbit.

4:21

And that's the potential for perineural spread

4:25

through the tributary of the second division of the

4:28

fifth cranial nerve, the maxillary nerve,

4:30

into the inferior orbital fissure.

4:33

Now,

4:33

let's continue to look. Yeah,

4:35

this is definitely worrisome.

4:36

Here we have a line of enhancing tumor

4:39

tissue going into the orbit.

4:43

From here,

4:44

we would also want to look for the foramen rotundum.

4:48

And

4:53

this is the foramen rotundum on the right side.

4:57

We compare the thickness of the

5:00

tissue to the foramen rotundum on the

5:02

contralateral side, and this is too wide.

5:06

So what I'm seeing here is tissue

5:09

in the foramen rotundum

5:10

coming to Meckel's cave

5:17

and comparing that to the thickness of the same

5:21

tissue in the foramen rotundum

5:23

on the contralateral side.

5:25

That is worrisome for perineural spread

5:27

which we have to be concerned with

5:30

with adenoid cystic carcinoma. Again,

5:31

50% to 60% rate of perineural spread.

5:35

The Vidian canal is the next area of concern.

5:39

This is the Vidian canal on the left side,

5:42

the Vidian canal on the right side.

5:44

I would probably pass the Vidian canal here

5:48

that is one of the tributaries.

5:51

here in the pterygopalatine fossa.

5:53

So, I wouldn't blame someone if they worried

5:56

about Vidian canal infiltration.

6:00

You?

6:01

So, tumor in the pterygopalatine fossa,

6:12

Vidian canal,

6:14

Vidian canal, coming back to foramen lacerum

6:19

which is where the carotid artery resides.

6:21

Is this too thick?

6:23

Depends upon your level of concern.

6:26

I can see how someone might worry about the entrance,

6:30

for sure, to the Vidian canal from the pterygopalatine

6:33

fossa. That's worth being concerned about.

6:39

The greater and lesser palatine foramina we've

6:41

talked about with regard to the hard palate. And frankly,

6:43

down here at the inferiormost portion

6:47

of the pterygopalatine fossa,

6:49

I don't see anything enhancing

6:52

that would be of concern.

6:57

Let's see whether they did any additional poll

7:00

sequences.

7:02

Here is a coronal scan.

7:07

And I believe that this is a true coronal

7:11

scan as opposed to a 3D reconstruction.

7:16

Here is that inferior orbital fissure.

7:18

Let me better zoom this up a little bit here.

7:23

Here's the inferior orbital fissure.

7:27

Tumor tissue entering the orbit.

7:33

And

7:39

this is the Meckel's cave.

7:45

And

7:48

this is pterygopalatine fossa with the tissue in it.

7:53

And this is the Vidian canal here

7:57

and here. It is a little bit fatter.

7:59

It a little bit larger.

8:01

I might worry about Vidian canal involvement there,

8:04

as well as, as we mentioned previously,

8:07

the foramen rotundum.

8:11

So, adenoid cystic

8:12

carcinoma affecting the nasal cavity,

8:15

minor salivary gland tissue with pterygopalatine

8:17

fossa infiltration and perineural

8:20

spread into the inferior orbital

8:22

fissure, the foramen rotundum,

8:25

and possibly the Vidian canal.