7. Soft tissue Masses

Question 1

Here is the simple part

Answer 1

only about 20-30% of them can be accurately diagnosed on MRl.

That’s because they are almost all T2 bright and enhance

Question 2

Here is the list I would know:

Answer 2

1. MFH — Malignant Fibrous Histiocytoma aka - Pleomorphic Undifferentiated Sarcoma
2. Synovial Sarcoma
3. Lipoma, Atypical Lipoma, Liposarcoma
4. Hemangioma
5. Myxoma

Question 3

Malignant Fibrous Histiocytoma (MFH)

Answer 3

Yes - they changed the name to Pleomorphic Undifferentiated Sarcoma “PUS.”

OLD people + CEntral (Prox arms and legs)

Thigh - most common

Association: Spontaneous Hemorrhage

Trivia: Bone infarcts can turn into MFH - “sarcomatous transformation o f infarct ” Trivia: Radiation is a risk factor.

Question 4

Answer 4

Features -About halfthe time it’s dark to intermediate on T2 (remember most soft tissue tumors are T2 bright). The way I remember this is the word “fibrous” - makes me think scar (which is dark).

Question 5

Synovial Sarcoma

Answer 5

Peripheral lower extremities
20-49

Close to the joint - But not in the joint

NEVER involve the joint

Question 6

Baker’s Cyst Fuckery

Answer 6

Baker’s Cyst MUST be located between the medial head of the gastrocnemius and the semimembranosus.

If it’s NOT - you should think Synovial Sarcoma - and “next step” MRI.

Question 7

There are 3 other ways to show Synovial Sarcoma

Answer 7

There are 3 other ways to show Synovial Sarcoma

(1) as the “triple sign”, which is high, medium, and low signal all in the same mass (probably in the knee) on T2,

(2) as the “bowl of grapes” which is a bunch of fluid -fluid levels in a mass (probably in the knee), or

(3) as a plain x-ray with a soft tissue component and calcifications - this would be the least likely way to show it.

Question 8

Synovial Sarcoma Trivia:

Answer 8

• Most sarcomas don’t attack bones; Synovial Sarcoma Can
• Most sarcomas present as painless mass; Synovial Sarcomas Hurt
• Soft tissue calcifications + Bone Erosions are highly suggestive
• ] They are slow growing and small in size, often leading to people thinking they are B9. D 90% have a translocation of X -18.

Question 9

Most common malignancy in teens/young adults of the foot, ankle, and lower extremity

Answer 9

Synovial Sarcoma

Question 10

When I say ‘‘Ball-like tumor” in the extremity o f a young adult, you say

Answer 10

Synovial Sarcoma

Question 11

When I say “Soft Tissue Tumor in the Foot ”of a young adult

Answer 11

Synovial Sarcoma

Question 12

Malignant Fibrous Histiocytoma (MFH ) vs Synovial Sarcoma

Answer 12

Question 13

Lipoma vs Atypical Lipoma vs Liposarcoma

Answer 13

*Liposarcomas tend to be DEEP (retroperitoneum) *Liposarcomas tend to be BIG
*Lipomas tend to be Superficial

Question 14

the most common liposarcoma in patients < 20.

Answer 14

Myxoid Liposarcoma

Question 15

Hemangioma

Answer 15

If they show you soft tissue plileboliths then hemangioma is the answer.

Question 16

Answer 16

Hemangioma

Hemangiomas don’t respect fascial boundaries
- they will infiltrate into stuff (this is a
somewhat unique feature).

• T2 bright (like most tumors)
• Flow voids. They have to show you flow voids
  (buncha dark holes).

Question 17

Myxoma

Answer 17

If this shows up on the exam, it is almost certainly going to be shown in the setting of Mazabraud Syndrome.

Question 18

Answer 18

Myxoma

What do Myxomas Look Like?

They are T2 bright (like every tumor),

but tend to be lower signal than muscle on T1 - which makes them sorta unique.

Question 19

CT vs MRI
for Lesion Characterization

Answer 19

Question 20

Pigmented Villonodular Synovitis (PVNS)

Answer 20

Synovial Proliferation + Hemosiderin Deposition

MRI will be obvious with blooming on gradient echo

Question 21

Primary Synovial Chondromatosis

Answer 21

The primary type is an extremely high yield topic.

It is a metaplastic / true neoplastic process
(not inflammatory) that results in the formation of multiple cartilaginous nodules in the synovium of joints, tendon sheaths, and bursae.

Question 22

Pigmented Villonodular Synovitis (PVNS) vs Primary Synovial Chondromatosis

Answer 22

Question 23

Secondary Synovial Chondromatosis

Answer 23

This is secondary to degenerative change, and typically seen in an older patient. There will be extensive degenerative changes, and the fragments are usually fewer and larger when compared to the primary subtype.

Question 24

Diabetic Myonecrosis

Answer 24

infarction of the muscle seen in poorly controlled type 1 diabetics

almost always involves the thigh (80%), or calf (20%)

Question 25

Lipoma Arborescens

Answer 25

The buzzword is “frond-like” deposition of fatty tissue.

can develop in a normal knee, it’s often associated with OA, Chronic RA, or prior trauma

Question 26

Answer 26

Lipoma Arborescens

On MRI it’s going to behave like fat - T1 and T2 bright with response to fat saturation.

Question 27

Answer 27

Tumoral Calcinosis

Question 28

Answer 28

Primary Synovial Chondromatosis
(it is “secondary” if there are degenerative changes)

Question 29

Answer 29

Metastatic Calcification

Seen in People with Renal Failure (or Hyperparathyroidism)
— people with Hypercalcemia

Can look similar to Tumor Calcinosis - although the labs are different (this has elevated Calcium) and Tumoral Calcinosis can have Fluid-Calcium Levels.