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Core > MSK: Soft Tissue Masses > Flashcards

MSK: Soft Tissue Masses Flashcards

1
Q

What are the salient soft tissue masses?

A
  • Malignant fibrous histiocytoma (AKA pleomorphic undifferentiated sarcoma)
  • Synovial sarcoma
  • Lipoma/atypical lipoma/liposarcoma
  • Hemangioma
  • Myxoma
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2
Q

What is the most common location for a pleomorphic undifferentiated sarcoma?

A

Proximal extremities (the thigh is the most common)

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3
Q

Pleomorphic undifferentiated sarcoma is most commonly seen in what pt population?

A

Older pts

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4
Q

Elderly female develops a thigh muscle hematoma after standing up from a chair…

A

Think pleomorphic undifferentiated sarcoma (these have a high risk of hemorrhage)

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5
Q

Classic imaging feature of pleomorphic undifferentiated sarcoma

A

Soft tissue mass that is often T2 dark/intermediate (most soft tissue masses are T2 bright)

Note: This used to be called a malignant fibrous histiocytoma (fibrous should make you think dark on MRI).

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6
Q

Bone infarctions can undergo malignant transformation to…

A

Pleomorphic undifferentiated sarcoma (AKA sarcomatous transformation)

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7
Q

Risk factors for pleomorphic undifferentiated sarcoma

A
  • Old age
  • Prior radiation
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8
Q

Synovial sarcoma is most common in what pt population?

A

Ages 20-40

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9
Q

What is the most common location for synovial sarcoma?

A

Peripheral lower extremities (close to a joint, but not in the joint)

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10
Q

Complex appearance of a Bakers cyst with internal flow on color Doppler…

A

Think synovial sarcoma

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11
Q

Popliteal fossa cyst that is not located between the semimembranosus tendon and medial head of gastrocnemius…

A

Not a Bakers cyst, be suspicious for synovial sarcoma and recommend an MRI

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12
Q
A

Synovial sarcoma

Note: “Triple sign” on T2 image (mass contains T2 high, intermediate, and low signal).

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13
Q
A

Think synovial sarcoma

Note: “Bowl of grapes sign” (multiple fluid-fluid levels in a soft tissue mass).

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14
Q
A

Irregular soft tissue calcifications near a joint, think synovial sarcoma

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15
Q

Soft tissue calcifications with adjacent bone erosions…

A

Think synovial sarcoma

Note: Most soft tissue sarcomas don’t cause bone erosions but synovial sarcomas can.

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16
Q

Clinical presentation of synovial sarcoma

A

Painful soft tissue mass

Note: Most other sarcomas are painless.

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17
Q

90% of synovial sarcomas have what genetic abnormality?

A

Translocation of X-18

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18
Q

What is the most common malignancy in teenagers to involve the foot/ankle/lower extremity?

A

Synovial sarcoma

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19
Q

Are synovial sarcomas fast growing?

A

No, they are usually slow growing (which can make radiologists mistake them for a benign lesion)

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20
Q

Ball-like tumor in the extremity of a young adult…

A

Think synovial sarcoma

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21
Q

Soft tissue tumor in the foot of a young adult…

A

Think synovial sarcoma

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22
Q
A

Think retroperitoneal liposarcoma

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23
Q

Imaging features that should make you suspicious for liposarcoma rather than a simple lipoma

A
  • Thick, nodular septations
  • Minimal fat content
  • Enhancing components

Note: Liposarcomas also tend to be deeper (e.g. retroperitoneal) rather than superficial.

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24
Q

What is the most common subtype of liposarcoma in pts under age 20?

A

Myxoid liposarcoma

Note: These are tricky because they usually appear dark on T1 and bright on T2 (and can be confused for a cyst). If you aren’t completely sure its a cyst, get post contrast imaging.

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25
Q
A

Think soft tissue venous malformation

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26
Q

6 m/o

A

Think infantile hemangioma

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27
Q
A

Think hemangioma

Note: Phleboliths on radiography and flow voids and macroscopic fat in a soft tissue mass on MRI.

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28
Q

Do sot tissue hemangiomas respect fascial boundaries?

A

No, they will infiltrate through fascial boundaries (a somewhat unique feature for a soft tissue mass)

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29
Q

Polyostotic fibrous dysplasia and multiple soft tissue myxomas…

A

Mazabraud syndrome (rare)

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30
Q

Next step: MRI demonstrates an avidly-enhancing soft tissue mass with flow voids…

A

Get radiographs (to look for phleboliths, which would be consistent with a soft tissue hemangioma/vascular malformation)

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31
Q
A

Think myxoma

Note: Soft tissue mass that is T1 dark relative to muscle, T2 bright,and peripherally or heterogeneously enhancing.

32
Q
A

Think Mazabraud syndrome (polyostotic fibrous dysplasia and multiple soft tissue myxomas)

33
Q

Treatment for osteosarcoma

A

Neoadjuvant chemotherapy (to kill micro metastases), followed by wide excision

34
Q

Treatment for Ewings sarcoms

A

Neoadjuvant chemotherapy and radiation, followed by wide excision

35
Q

Treatment for chondrosarcoma

A

Usually just wide local excision

36
Q

Treatment for giant cell tumor

A

Usually excision with arthroplasty (because these extend to the articular surface)

37
Q

Pigmented villonodular synovitis

A

An uncommon benign neoplastic process that results in synovial proliferation and hemosiderin deposition

38
Q

What is the most common location for pigmented villonodular synovitis?

A

The knee (65-80%)

39
Q

Radiographic findings seen in pigmented villonodular synovitis

A
  • Joint effusion
  • +/- marginal erosions (with preservation of the joint space)

Note: It is not possible to distinguish pigmented villonodular synovitis from synovial chondromatosis on radiography alone.

40
Q

GRE

A

Pigmented villonodular synovitis

Note: Blooming artifact from hemosiderin deposition on GRE.

41
Q

Treatment for pigmented villonodular synovitis

A

Complete synovectomy

Note: Recurrence is common (20-50%).

42
Q

Pigmented villonodular synovitis is unusual in pediatric pts, but when it occurs it is usually…

A

Polyarticular

43
Q

What are the major types of synovial chondromatosis?

A
  • Primary
  • Secondary (due to degenerative changes)
44
Q

Pathophysiology of primary synovial chondromatosis

A

Primary synovial chondromatosis is a neoplastic precess resulting in the formation of multiple cartilaginous nodules in the synovium of joints, tendon sheaths or bursae. These nodules then progress to loose bodies.

45
Q

What is the most common location for primary synovial chondromatosis?

A

The knee (70%)

46
Q

Primary synovial condromatosis is most common in what age group?

A

40s-50s

47
Q

What is the characteristic appearance of intraarticular loose bodies in primary synovial chondromatosis?

A

Numerous, uniformly sized loose bodies +/- chondroid calcification

48
Q
A

Primary synovial chondromatosis

49
Q

Treatment for primary synovial chondromatosis

A

Removal of intraarticular loose bodies +/- synovectomy

50
Q
A

Primary synovial chondromatosis

51
Q

Is pigmented villonodular synovitis or primary synovial chondromatosis associated with hemarthrosis?

A

Pigmented villonodular synovitis (this is why there is hemosiderin deposition in PVNS)

52
Q

Which often calcifies: pigmented villonodular synovitis or synovial chondromatosis?

A

Synovial chondromatosis

Note: PVNS never calcifies.

53
Q
A

Think secondary synovial chondromatosis

Note: This usually has fewer and larger intraarticular loose bodies.

54
Q

What is the most common location for diabetic myonecrosis?

A
  • Thigh (80%)
  • Calf (20%)
55
Q

Poorly-controlled type 1 diabetic

A

Diabetic myonecrosis

Note: Do NOT biopsy this (delays recovery time and has a high complication rate).

56
Q
A

Lipoma arborescens

Note: “Frond-like” deposition of fatty tissue in the synovial lining of joints/bursa.

57
Q

Lipoma arborescens is most common in what age group?

A

50s-70s

58
Q

What is the most common location for lipoma arborescens?

A

The suprapatellar bursa of the knee

59
Q

Risk factors for lipoma arborescens

A
  • Prior trauma
  • Osteoarthritis
  • Rheumatoid arthritis
60
Q
A

Lipoma arborescens

Note: “Frond-like” deposition of fatty tissue in the synovial lining of joints/bursa. It behaves like fat (responds to fat saturation).

61
Q

Knee joint ultrasound

A

Lipoma arborescens

Note: “Frond-like” deposition of fatty tissue in the synovial lining of joints/bursa.

62
Q
A

Think tumoral calcinosis

Note: Big, lobular calcium near a joint.

63
Q
A

Think tumoral calcinosis

Note: Big, lobular/cystic calcium deposits near a joint with fluid-calcium levels (arrows).

64
Q

What is the most common location for tumoral calcinosis?

A

Greater trochanteric bursa

Note: Hips, elbows, and shoulders are common. Knee is rare (helps distinguish from synovial chondromatosis).

65
Q

Pathophysiology of tumoral calcinosis

A

Hereditary phosphate metabolism issue (calcium levels are normal, but phosphate levels are usually abnormal)

66
Q
A

Think metastatic calcification

Note: Seen in pts with hypercalcemis (e.g. renal failure or hyperparathyroidism).

67
Q

Which features should make you think metastatic calcification rather than tumoral calcification?

A
  • Presence of renal and lung calcifications
  • Hypercalcemia (tumoral calcinosis will have normal calcium levels)

Note: If you see fluid-calcium levels, think tumoral calcinosis.

68
Q
A

Think myositis ossificans

Note: Circumferential calcifications with a Lucent center. Do NOT biopsy. This can look scary on MRI if imaged during early phases (due to edema and avid enhancement).

69
Q
A

Cortical desmoid

Note: This is not actually a desmoid, but a tug lesion from the medial gastrocnemius and ADDuctor magnus.

70
Q
A

Synovial herniation pit (do not touch lesion)

Note: Characteristic location in the anterosuperior femoral neck. This likely has an association with femoroacetabular impingement.

71
Q
A

Osteoid osteoma

Note: This was originally mistaken for a synovial herniation pit on MRI.

72
Q
A

Synovial herniation pit

73
Q

Special considerations when performing a pelvic bone biopsy

A

Avoid crossing the gluteal muscles (which may be needed for reconstruction)

74
Q

Special considerations when performing a knee bone biopsy

A
  • Avoid the joint space (including communicating bursa, such as the supra patellar bursa)
  • Avoid crossing the quadriceps tendon
75
Q

Special considerations when performing a shoulder bone biopsy

A

Avoid the posterior 2/3 (the axillary nerve runs posterior to anterior, so a posterior resection will denervate the anterior 1/3)

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