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Dr. P here. This is a 34-year-old man who had a mass

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3 00:00:05,010 --> 00:00:08,119 on his foot that was biopsied, and the biopsy came

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back nodular fasciitis, and that is a good lesson.

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And the lesson is, when you have pathology in

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either the bone or soft tissues, you want a bone

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or soft tissue bone pathologist looking at your

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stuff because that was not the correct diagnosis.

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And he presents somewhat later with this mass.

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There's a few characteristics of

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this mass on T2, T1, and contrast

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enhanced T1 with extensive enhancement

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that support the diagnosis

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of an aggressive neoplasm.

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First, the enhancement is intense.

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Even though it's not dynamic,

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it's an equilibrium-phase enhancement.

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There's a lot of enhancement.

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Then you look at the lesion,

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and it is very heterogeneous inside.

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In fact, when you look very carefully

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at it, it's very heavily septated,

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which plays into the differential diagnosis.

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Next, it has incredible disrespect for boundaries.

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It's even disrespecting the skin.

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It's growing into the dermis.

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If you look at the T1-weighted image and the

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contrast-enhanced image, it's crossing into

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the volar or plantar aspect of the foot.

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So that too suggests an aggressive process.

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So, the differential diagnosis here has to

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include a large complex primary soft

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tissue neoplasm, and the one that would

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work the best here is synovial sarcoma.

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Now there is a differential diagnosis.

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You can get

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synovial chondromas, but they are small.

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You can get an extra-articular soft

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tissue osteogenic sarcoma, but they like

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the upper extremities, they like the

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thigh, and they like the buttock region,

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so this is not a good place for that.

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Soft tissue fibrous sarcoma.

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They're not going to be as heterogeneous

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or as bright on the T2-weighted image,

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so the T2-weighted image is very helpful here.

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One lesion that might be tough to

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differentiate from this lesion,

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but doesn't necessarily like the foot,

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is soft tissue hemangiopericytoma.

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Malignant fibrous histiocytoma,

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it doesn't really have a predilection for

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the foot, it really likes the thigh.

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Whereas this lesion, synovial sarcoma,

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which is the answer, likes the knee and the foot,

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and occasionally will occur in the thigh.

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Giant tophus.

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Well, you'd like to see some erosions

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and some signs of gout, but this would be

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the biggest tophus that I've ever seen.

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And tophagous gout doesn't

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enhance like this, so that is out.

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Myositis ossificans can look really ugly and

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really aggressive, but you get the zonule

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phenomenon, where you get enhancement around

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the outside, and then progressively over time,

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the enhancement may encroach into the center.

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So that's out as well.

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And then you have tumoral calcinosis,

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where you have calcification in the center and

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a bursa-like structure around the outside.

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And on laboratory evaluation, you have

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an abnormal calcium phosphorus product.

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Sometimes they have renal insufficiency.

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So this is synovial sarcoma.

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Now you hear the word synovium.

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There is a benign synovioma of

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the knee joint or of the joint.

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That is not the same lesion.

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It is non-aggressive,

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it is benign, and they're extremely rare.

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These lesions tend to occur in the soft tissues.

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They like to be near tendons,

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tendon sheaths, bursa, less commonly fascia,

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and aponeuroses and the interosseous membrane.

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Again, they're extra-articular,

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which belies their name.

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And, as said, they have a predilection

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for the knee and the foot.

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The average age is about 35 years of age,

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and they tend to calcify about 25% of the time.

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Now, when they calcify heavily,

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they have a better prognosis.

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But for the most part, this lesion

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does not have a great prognosis.

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It does metastasize to the lung.

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And even the lung lesions may calcify.

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Despite its large size, one weird

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aspect about this lesion is it doesn't

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really eat away at bone very much.

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Now because it's composed of epithelium and

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fibrous septa, you get this glandular-like

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appearance with this heavy septation, although

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it's not the organized, brain-like, collagenous,

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parallel septations that you see with very

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aggressive, large, giant, desmoid-like lesions,

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including plantar fibromatosis, which is something

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that occurs in the plantar fascia most commonly.

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About 90% of these have

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translocation of chromosome X to 18.

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And it is believed that these arise from

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pluripotential stem cells from the limb bud.

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There are a few types of these,

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and these include the biphasic type, in which

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you have fibrous and glandular tissue.

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That's this type right here.

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Then monophasic, where either

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fibrous or glandular tissue dominate.

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Those are much less common.

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You have the poorly differentiated type which

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very difficult to differentiate from any other

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poorly differentiated sarcoma other than location.

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You have pure glandular types and then

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you have the heavily calcified type

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which has a pretty good prognosis.

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There is some histologic similarity

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to hemangiopericytoma which can

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make this diagnosis very difficult.

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So, we have some 3D images here that we acquired

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to map out this lesion for potential resection.

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Here is the short axis, the sagittal

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long axis, and the coronal long axis.

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And the lesion has this

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necrotic-looking center to it.

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And you can see its intimate

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contact with the adjacent bone.

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Then we reconstructed it sagittally.

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We reconstructed it in the axial projection.

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It's a nasty lesion.

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It's extra-articular, it likes the foot,

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it likes the knee, it has septations

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and glandular components to it.

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It is the synovial sarcoma.

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Dr. P out.