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Hi, Dr. P here with a 56-year-old man

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3 00:00:05,000 --> 00:00:08,000 with an enlarging mass in the great toe.

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It's a coronal T2, non-fat suppressed.

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A sagittal, simple T1.

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And somebody reported this as a

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cystic mass, and I can see why.

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It's very bright on the water-weighted image,

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but lots of things are.

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And just like an ultrasound when

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you have criteria for a cyst,

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good through transmission, hypoechogenicity,

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homogeneity, usually oval or round in shape, etc.

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On MR, you have criteria too, and one of those

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criteria is that the signal is water-like,

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matches water on the T2-weighted image, and on

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the T1-weighted image, it matches water again.

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Water-like urine, like signal in the bladder.

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If we just look here, and maybe we shrink

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down a little bit, you'll see that the

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signal of muscle is about the same,

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maybe even a little lower than our mass.

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So this does not meet the criteria

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of simple fluid or a simple cyst.

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It's got to be a proteinaceous

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water signal intensity mass.

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Now a couple of descriptors about this mass.

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It's serpiginous.

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It's septated.

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And in some respects, that makes you

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think a little bit about a hemangioma.

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Although the little lobules

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of hemangioma are smaller.

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So let's go through a differential diagnosis here.

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And let me bring down the sagittal T2 now,

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and show you the architecture of this mass,

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which is similar to the long-axis view.

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And the thing that I liked about this mass as

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a first choice was epidermoid, because of its

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size and its location, implantation epidermoid.

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Epidermoids are inclusion lesions,

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And what else might we consider here?

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Well, somebody mentioned a tenosynovial cyst

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in the report, and if you bring down the

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T2-weighted image, there is some tenosynovial

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fluid, but it is not communicating with our

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mass, nor is our mass tubular like a tenosynovial

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cyst, so I don't like that diagnosis.

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Another water signal type mass that's

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not simple water, that would have this

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signal characteristic, is a myxoma.

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So it would be an awfully odd location

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for a myxoma or the myxomatous family of

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tumors and the only way to exclude that as a

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possibility would be to inject this patient

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and look for the absence of enhancement.

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Then another thought would be a glomus tumor.

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They like to occur in the nail bed

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but I have seen them in the tuft

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portion of the finger and the toe.

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I have never seen one this big.

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I have never seen one with

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this shape and architecture.

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So I don't like glomus tumor, nor was

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the history supportive of that diagnosis.

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What about a capsular cyst?

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Now that would be a strong consideration here.

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But in order to have a capsular

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cyst, let's look at the capsule.

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And let's go to the sagittal.

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There's only a little bit of fluid in the capsule,

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and I cannot see this mass

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communicating with the capsule.

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And the main difference between a capsular cyst

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and a ganglion cyst, which is a consideration

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here, is a capsular cyst is lined by epithelium.

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A ganglion cyst is lined by fibrous tissue.

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A ganglion cyst has an obvious macroscopic

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communication to a fluid-filled joint.

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A ganglion, not so much.

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There might be a microscopic

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communication, but not a macroscopic

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one and usually the joint is dry.

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So ganglion pseudocyst would be a consideration

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along with epidermoidoma or inclusion cyst.

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Another good consideration

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would be cystic schwannoma.

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You're near the neurovascular bundle.

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It's a little big for that diagnosis.

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The shape is a little weird.

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The only way you're going to exclude it

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is with a contrast injection,

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although the patient should report some neurologic

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symptoms, which this patient did not.

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Just simply a slow-growing mass.

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So, I'm not keen on the

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diagnosis of cystic schwannoma.

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And finally, there's varix.

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Now, if you're going to make the diagnosis of a varix,

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and there are veins in this location,

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you better be able to connect this with a vein.

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And I can't connect it with any tubular

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longitudinal structure that is reminiscent

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of a vein or an artery for that matter.

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But an artery wouldn't play

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into the diagnosis here.

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So my choices would be epidermoidoma

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and ganglion pseudocyst.

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They did not bring the patient back for injection.

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It turned out to be a ganglion pseudocyst.

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This is one of the bigger ones that I've seen.

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It is not a common location.

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Ganglion cysts can be very septated,

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but they do not, because they're

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pseudocysts surrounded by fibrous tissue,

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they do not contain bodies.

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They do not contain metaplasia.

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They do not contain pieces of chondral tissue.

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So for the most part, the internal constituents

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of a ganglion pseudocyst are clean.

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It may have a very small microscopic tail.

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It goes to, say, the joint, or goes to a tendon.

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The tail is important in the diagnosis.

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I'm not sure I see a great tail

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here in this particular instance.

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And frankly, ganglion cyst was my

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second choice, not my first choice.

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But that is the final diagnosis.

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Giant ganglion pseudocyst of the great toe.

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Let's move on, shall we?

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Dr. P. out.