Case:

This was posted on YouTube as Case of the Day 209.

A mid-30s individual presented with a long standing history of waxing waning pain and swelling of the knee

What did this mean?

• Synovial hypertrophy?

• Blood/hemosiderin?

• Tenosynovial giant cell tumor?

• Infection?

• Fat?

The video discusses the case and the final diagnosis.

Other Differentials

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• 71 Cases

• 16 Cases of the Day

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Case:

This was posted on YouTube as Case of the Day 208.

40-year old presented two years ago with a mass in the distal left thigh.

Post surgery, there was recurrence two years later.

In such situation we also do a whole thigh survey.

The full case is at

The lesson here is to always trace the nerve and look at the whole limb for skip lesions.

Other Soft Tissue Sarcoma Cases

About Skip Lesions

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• 70 Cases

• 16 Cases of the Day

• 5 Lectures

Case:

A 67-year old presented with elbow pain.

The radiograph (Fig. 1) shows an osteolytic lesion in the metaphysis involving the lateral condyle with a sclerotic rim, but with a shaggy periosteal reaction. Despite the sclerotic rim, this should be assumed to be an aggressive lesion, unless proven otherwise.

The MRI (Fig. 2) shows the osteolytic lesion with marrow edema (arrow in B) with crenated margins with extra-osseous spread anteriorly (arrows in A and C).

This was also confirmed on the CT scan (Fig. 3).

This is the stage where you ponder the next step. Biopsy or further imaging.

A biopsy was done and showed a clear cell malignant tumor, likely a renal primary.

A PET (Fig. 4) showed the primary lesion arising from the upper pole posteriorly.

In any person above the age of 34, unless there are specific findings pointing towards a primary bone tumor (chondroid or osteoid matrix) or infection (marrow edema, abscess, sequestrum), a focal bone lesion should be assumed to be metastasis, myeloma or lymphoma unless proven otherwise.

Last year’s lecture on Approach to Bone Tumors covered this

The first case was also about this

Other Metastases Cases

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• 69 Cases

• 16 Cases of the Day

• 5 Lectures

Case:

37-years old presented with a knee swelling. Only films were available for review.

The radiograph shows an expansile osteolytic lesion in the distal femur with thinning of the anterior cortex with a narrow zone of transition without periosteal reaction or cortical break, epimetaphyseal and extending into the diaphysis (Fig. 1).

This suggests a slow-growing, perhaps benign or low grade malignant lesion.

An epi-metaphyseal, juxtamedullary lesion in this age group should trigger a diagnosis of giant cell tumor (GCT), but GCTs rarely have sclerotic rims.

More importantly there is a matrix (arrow in Fig. 1B), which shows a rings and arcs appearance, suggestive of cartilage.

A cartilage tumor like this is too big and eccentric for an enchondroma, though rarely a chondroblastoma or chondromyxoid fibroma could be this big. Both would show marrow edema on MRI presenting as “benign aggressive lesions”. If not, then this is a chondrosarcoma, either Gd 1 or Gd 2.

The CT (Fig. 2) confirms the chondroid matrix.

The axial T2 MRI (Figs. 3, 4) shows the typical lobulated septate appearance of a cartilage tumor with no marrow edema on the sagittal STIR (FIg. 5) image.

The histopathology (Figs. 6, 7) show a Gd II chondrosarcoma.

A careful perusal of the radiographs often allows us to make a reasonable diagnosis. The MRI then helps confirm and the histopath then validates. Reading an MRI without the radiograph can lead to all sorts of problems

Other Chondrosarcoma cases

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• 16 Cases of the Day

• 5 Lectures

Case:

24 years old known to have hereditary multiple osteochondromas (HMO) earlier called multiple hereditary exostoses (MHE), presented with a growing lesion in the left upper arm.

X-ray (Fig. 1) shows an osteochondroma arising from the lateral aspect of the proximal left humerus with no worrisome features. Note the sessile osteochondroma medially, which is atypical appearance in patients with HMO.

MRI (Fig. 2) was interpreted to be worrisome for malignant transformation and a biopsy was done.

A close look at the MRI shows (Fig. 3) shows an average cartilage cap thickness of 4 mm and the maximum at two different areas of 8 mm with no osteolytic or bone destruction or extralesional soft tissue. There is truly no suggestion of malignant transformation, which was proven on biopsy as well.

Osteochondroma is defined as a benign cartilaginous neoplasm consisting of a bony projection covered by a cartilage cap, arising at the external surface of bone and containing a marrow cavity that is continuous with that of the underlying bone.

Fig. 4 shows how to measure the cartilage cap and the features that suggest malignant transformation.

Fig. 5 shows that the way I had shown the measurement in Fig. 2 is incorrect (A) and the correct way would be as shown in Fig. 5B, in which the cartilage cap thickness is just 3.6 mm.

Fig. 6 is a new paper on the subject that says the following.

1. Secondary chondrosarcomas are typically seen in patients above the age of 30

2. While the rate of malignant transformation is 1% in patients with solitary osteochondromas, it rises to 5% in those with HMO. In this paper, patients with HMO were 8 times more likely to undergo malignant transformation than those without.

3. A cartilage cap thickness of > 3.0 cm has a high specificity for malignant transformation

4. A cartilage cap < 2.0 cm has a high specificity to rule out malignant transformation.

5. Sessile osteochondromas are more likely to undergo malignant transformation than pedunculated ones.

Other Osteochondroma Cases

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• 67 Cases

• 16 Cases of the Day

• 5 Lectures

Case:

14-years old presented with a leg swelling.

The radiograph (Fig. 1) shows an expansile, osteolytic lesion with a narrow zone of transition and a sclerotic rim, diaphyseal in location, central medullary. No marrow edema, cortical break or extra-osseous extension is seen.

This is a benign lesion. Trabeculated, expansile lesions like these in general can be

1. Non-ossifying fibroma / osteofibrous dysplasia / fibrous dysplasia

2. Giant cell tumor

3. Aneurysmal bone cyst (ABC)

4. Hemangioma

5. Desmoplastic fibroma

6. Brown tumor

The location and age rule out all except aneurysmal bone cyst. Hemangioma is very rare. The serum calcium and alk phos were normal.

The MRI (Fig. 2) shows an expansile T2 intermediate to dark lesion (axial - A, coronal - B and sagittal - C). There are no fluid levels. The lesion is arterially enhancing (Fig. 3) lesion.

A biopsy (Fig. 4) shows a giant cell containing benign tumor.

This combination of a giant cell containing tumor with an expansile, trabeculated appearance in the diaphysis is consistent with a solid-variant ABC.

When a lesion looks like an ABC on a radiograph but does not have fluid levels and pathology shows a giant cell containing benign lesion, that is when we can make a diagnosis of solid variant ABC.

The video (YouTube Members Only) discusses the case, 2 other similar cases, the literature, then subperiosteal and surface ABCs that can also have solid variants and ends with the concept of USP6 positive neoplasms.

Other ABC Cases

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• 66 Cases

• 16 Cases of the Day

• 5 Lectures

Case:

48 years old had progressive knee pain.

Radiograph (Fig. 1) shows large articular margin erosions (arrows) along the peripheral margins with mild periarticular osteopenia.

The T2 sagittal image (Fig. 2) shows large synovial nodules (arrows), T2 dark with an enlarged popliteal node (red arrow).

The PD fat sat coronal image (FIg. 3) shows marrow edema with free margin erosions and large central erosions (arrows).

The erosions (arrows) are much better appreciated on the T1 coronal image (Fig. 4).

This is a mono-articular arthropathy. While tenosynovial giant cell tumor (see case below) may occur with T2 dark large intra-articular nodules, they rarely produce free edge erosions and marrow edema.

A mono-articular arthopathy should be assumed to be infective unless proven otherwise and this pattern is commonly seen with tuberculosis.

A biopsy confirmed the diagnosis.

This case also shows Phemister’s triad.

Other Tuberculosis Cases

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• 65 Cases

• 16 Cases of the Day

• 5 Lectures

Case:

66-years old man with gradually progressive pain, without fever in the right shoulder.

MRI showed a destructive arthropathy, as did a CT scan. Neuroarthropathy was ruled out with an MRI cervical spine.

The video describes the findings and the final diagnosis obtained on USG guided aspiration.

Full Video

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Case:

23-years old known to have tenosynovial giant cell tumor - the gradient image (lower left image) shows blooming of hemosiderin (green arrows).

The nodular synovitis is T2 dark in the sagittal and axial images. This used to be earlier called pigmented villonodular synovitis (PVNS).

To know more about the tumor.

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Case:

25-years old with knee pain.

X-ray shows an osteolytic lesion with a sclerotic rim - this is a benign lesion.

MRI shows marrow edema - this is now a “benign aggressive” lesion.

The lesion is partly T2 dark and shows a lamellated pattern of enhancement and is eccentric juxtamedullary.

A biopsy was done.

The findings are characteristic of chondromyxoid fibroma.

To know more about the tumor.

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Case:

26-years old presented with progressive pain in the left thigh and fever.

The first MRI showed marrow edema with mild periosseous edema and no other pathology. The radiograph 16 days later showed permeative cortical involvement and then a PET was done followed by a CT scan and CT guided biopsy.

The video discusses the case and shows the rapid progressive of disease in 24 days and the evolution of a sequestrum, involucrum and cloaca.

The final diagnosis was Staphylococcus aureus hematogenous osteomyelitis of the femur.

Video

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Case:

16-years old with an osteolytic lesion in this specific Diard 6 area of the calcaneum.

Is it cyst? lipoma? Does it matter? Are they perhaps part of the same continuum?

The video describes the case and revisits another case -

- to understand all these concepts and the possible etiology of these uniquely situated lesions.

Video

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Previous Case of the Day Posts

Previous Similar Case

Case:

10-years old girl with a left 1st metatarsal lesion with marrow edema, but no cortical break or extra-osseous soft tissue mass or collection.

A biopsy showed inflammation, ruled out tumor, with no evidence of obvious infection.

A whole body MRI was done to clinch the diagnosis.

The video explains the case and the final diagnosis.

Video

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Previous Case of the Day Posts

Previous Similar Case

Case:

15-yrs old diagnosed with osteosarcoma of the distal left femur.

This video describes the case, the different aspects of staging, specifically why it is important to look for transphyseal spread - epiphyseal involvement and skip lesions in the same bone and how to go about doing this.

Video

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Previous Case of the Day Posts

Case:

13-yrs old with a proximal tibial, bone forming, aggressive lesion, likely osteosarcoma with one failed biopsy.

What do you biopsy? How? Why?

The video discusses the case and the thought behind the path chosen and the final diagnosis.

Video

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Previous Case of the Day Posts

Case:

A 70-years old presented with a slowly growing mass in the right thigh.

An MRI was done.

Eventually a CT guided biopsy was done.

What do you think is the diagnosis?

The answer is up

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Previous Case of the Day Posts

MRI shows a typical appearance that is characteristic of FAVA, a newly introduced term.

The video explains the diagnosis and shows another similar case..

Video

Case:

A 60-years old presented with a 2-years history of throbbing pain in the distal phalanx of the thumb.

What do you think is the diagnosis?

The answer is up.

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Case of the Day Series

Lecture:

This is a lecture I gave on 15th Feb 2025 at an Orthopedic Infections conference.

It discusses common mimics of osteomyelitis in the appendicular skeleton including tumors with and without marrow edema, CNO and fractures. Many of these cases have already been discussed on this site.

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Case:

A 22-year old presented with pain and swelling in the right thigh for a month with a history of fall 3 weeks prior to the symptoms.

What do you think is the diagnosis?

The answer is up

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