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Dr. P here.

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3 00:00:02,400 --> 00:00:06,660 I've got a 66-year-old woman with a mass

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growing on the dorsal aspect of her foot.

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I do not know whether it's

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getting bigger or smaller.

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I have a T1 Spin echo.

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Here's the mass surrounding the extensor hallucis.

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There it is on a T2 spin echo

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without fat suppression.

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It is not white.

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It's not very watery.

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It's more intermediate in signal intensity.

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And then on the right-hand side is the T1 spin

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echo image showing what I would consider an

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obliquely oriented elliptical-shaped mass.

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If I just kind of wrap my pen

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around it right here, I think you

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can see it pretty well right there.

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And then here's the mass in the short axis

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projection, no problem for you to see that.

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Now let's scroll up and down, and you

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can see it goes away, then it comes

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back, and then it goes away again.

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And I think our team generated a very

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reasonable differential diagnosis.

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I'll give you the muscular atrophy.

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I'll give you the osteoarthritis

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of the great toe right now.

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I'll give you the fact that

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the patient has had a distal

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osteotomy, and let's just focus on the mass,

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because that's our purpose here today together.

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So we said, we thought it could be

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a tenosynovial reaction, as might

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occur with, say, RA, with some pannus.

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Totally reasonable, although what's

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unreasonable about that differential

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diagnosis is we didn't see any arthropathy.

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Erosions, juxta-articular

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edema, or pannus anywhere else.

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So that's a little weird.

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So, we chose giant cell tumor of

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tendon sheath as our first choice.

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It has a pretty good signal for that.

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If we go to the more water-weighted image,

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which might allow us with some advantage

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to see some hemosiderin deposition or some

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blooming phenomenon, we see none of that.

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We just see some higher signal intensity,

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which doesn't really help us a lot.

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Now, it would have been nice

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to have a gradient echo image.

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Let's see if we have one somewhere.

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We don't, but here's another very

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heavily water-weighted image.

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And once again, the signal intensity,

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if I blow it up for you, is quite gray.

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So we have these pretty little scans,

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all in a row, and there is no iron,

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there is no hemosiderin deposition.

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So giant cell tumor of tendon sheath,

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while it was the diagnosis that we

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picked, we didn't feel wonderful about it.

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It got biopsied, and the diagnosis

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came back as granuloma annulare.

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Now there are four types of this entity,

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which occurs mostly in children and young adults.

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And this lady is not a child or a young adult.

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So that made it all the more surprising localized,

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generalized perforating and subcutaneous.

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Now some other names that you may or may not

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be familiar with are benign rheumatoid nodule.

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That's kind of confusing.

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Pseudo-rheumatoid nodule.

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I've heard that kicked around

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and palisading granuloma.

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I've heard that.

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Kicked around as well.

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These are usually painless subcutaneous lesions.

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I encounter them in my practice about twice

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a year because I see so many knee MRIs in the

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pre-tibial region and it does like that region.

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Sometimes, these lesions will grow fast.

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Now, I'm not sure if the annular

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word is related to the shape of it.

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In fact, I think it's not.

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But I will say, if you go back and

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look at the T1-weighted image, it does

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have this kind of annular shape to it.

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And that has been my experience

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even with the pre-tibial ones too.

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It's kind of a long, moderately

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long, sessile lesion.

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So the final diagnosis here

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was granuloma annulare.

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The take-home message is that it

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occurs in children and young adults.

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It likes the pre-tibial region.

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This happens to be a freaky

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diagnosis in this case.

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We gave you a reasonable differential diagnosis.

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Dr. P signing out.