Pathological significance of soft tissue and fat planes

1. PATHOLOGICAL SIGNIFICANCE
OF SOFT TISSUE AND FAT
PLANES

2. • These lesions range from non-neoplastic conditions to
benign and malignant tumors.
• Presently, imaging provides a limited ability to reliably
distinguish between benign and malignant soft-tissue
lesions.
• The primary goal for the imaging referral is to confirm the
presence of a mass and to assess its extent in
preparation for possible treatment

3. • In an important subset of cases, characteristic clinical and
imaging information can help to narrow the differential
diagnosis.
• These characteristics include
o Clinical history,
o Lesion location,
o Mineralization on radiographs,
o Signal intensity (SI) characteristics on magnetic resonance
(MR) images.

4. • Soft tissue arises from the
mesenchyme, which
differentiates during
development to become
fat, skeletal muscle,
peripheral nerves, blood
vessels, and fibrous tissue
Lipomas contain cells that produce fat; however, lipomas
do not necessarily arise from fat cells.

5. Pathology
• Soft-Tissue Tumors and Tumor like Lesions
• Soft tissue injury

6. Imaging techniques for the evaluation
of soft tissue tumors
• X-Ray
• Ultrasound
• CT
• MRI
• Bone scan

7. • It is impossible to arrive at a single diagnosis for many of the
lesions encountered.
• applying a systematic approach,
(a) can arrive at a diagnosis for the subset of lesions that have
characteristic appearances
(b)can narrow the differential diagnosis for lesions that
demonstrate indeterminate characteristics.

8. • Aim for evaluate whether the soft tissue tumor is
actually originating from the bone and is in fact an
osseous lesion
• provide an assessment of osseous involvement by a
truly soft tissue tumor (such as remodeling,
periosteal reaction, or overt cortical destruction).
• Radiographs also evaluate for the presence of
mineralization

10. • It is highly dependent on the skill of the radiologist/sonographer
and the quality of the equipment.
• US is ideally suited as initial triage imaging modality
• Following the confirmation of a soft tissue mass, sonographic
assessment of its nature (ie, solid versus cystic), size, shape,
number, vascularity (color or power Doppler), location, and
anatomical relationships to adjoining structures aids in
characterization and determining whether further imaging or biopsy
is required

12. Signs of malignancy on U/S
• Large size at presentation (>5 cm),
• Rapid growth,
• Deep location,
• Hyperemic chaotic-type vasculature on Doppler
Tumors that have the one or more of this feature should be evaluate with
other modality and go for biopsy

13. • The best soft tissue contrast,
• Multiplanar capability, and lacks ionizing radiation; thus,
Vascular structures can also be more easily recognized, even
without the need of intravenous contrast agents.
• MRI should be considered instead of (or in addition to)
US whenever there is clinical suspicion of malignancy and/or
painful, deep-seated, or (fast)-growing masses.

14. • At least two orthogonal planes and include T1-weighted and
fluid-sensitive weighted sequences, with or without fat
suppression.
• Additional sequences to consider include gradient-echo
imaging for the detection of hemorrhage,
• T1-weighted fat-suppressed images to differentiate fat from
hemorrhage,
• static-enhanced imaging after contrast administration.

15. T1
Low
T2
Low
Cortical bone
Mature fibrous tissue
(ligaments and tendons)
Calcification
Blood vessels
T1
Low
T2
High
Fluids as:
CSF
Effusion
Ascites
Urine
Vitreous humorous
T1
High
T2
Low
Fat as:
Subcutaneous fat
Bone marrow
Dermoid
Hamartomas
T1
Low
T2
High
Blood (subactue
hemorrhage)

16. • Should carefully evaluate the lesion in terms of its
o Size,
o Site,
o Morphology and borders,
o Relationship to adjacent structures, and multiplicity
o Internal signal characteristics on all imaging
sequences.

18. • Ill-defined borders;
• Infiltration or invasion of adjacent
structures;
• Size greater than 5 cm;
• Deep location;
• Heterogeneous T1 and T2 signal
intensity;
• High T2 signal intensity of surrounding
tissues,
• Indicative of edema disproportionate
to the size of the lesion,
• Necrosis;
• Intralesional hemorrhage;
• Bone or neurovascular involvement;
• Early contrast enhancement, followed
by plateau or washout; and
• Peripheral, nodular, or heterogeneous
internal enhancement
MRI features of soft-tissue lesions that are
suggestive of malignancy

20. • Ill-defined borders;
• Infiltration or invasion of adjacent structures;
• Size greater than 5 cm;
• Deep location;
• Heterogeneous T1 and T2 signal intensity;
• High T2 signal intensity of surrounding tissues,
• Necrosis
• heterogeneous internal enhancement

27. v• Site: ankle
• Location:
superficial
• Size: <5 cm
• Borders/
morphology:
regular smooth/
homogenous
• Adjacent
structures: intact

28. Site: hand
Location: deep
Size: >5 cm
Borders/ morphology: ill defined /Inhomogenous
Adjacent structures: involved
Heterogonous post contrast enhancement

29. Site: wrist
Location: deep
Size: >5 cm
Borders/ morphology: well defined lobulated
/Inhomogenous
Adjacent structures: intact

30. Significance of Soft tissue pathology in trauma
• Soft tissue swelling involving fat planes should conform to the
area of underlying soft tissue or bone injury.
• "Swelling seen in an area not associated with an observed
fracture should initiate a search for an additional abnormality
to explain the swelling.

31. Effusion/Lipohaemarthrosis
• The lateral horizontal ray knee view is the one projection
where we see this appearance most commonly.
• A lipohaemarthrosis indicates that there is a fracture that
communicates with the knee joint.

32. • There are two fat pads in the knee
• The suprapatellar fat pad
• The prefemoral fat pad

35. Ankle Effusion- The Tear drop Sign
• suggests a significant injury to the ankle joint.
• The anterior and posterior juxta-capsular region of a normal
ankle joint should appear as a fat-like density.
• In the presence of an ankle effusion, the capsule can become
distended and may appear to have a fluid-like density

37. Kager's Fat Pad
• it is not uncommon for ankle injuries to involve Kager's fat pad.
• A careful examination of the density, shape and borders of
Kager's fat pad can provide indicators of bony injury to the ankle.
An abnormal Kager's fat pad does not indicate definite bony
injury to the ankle.

39. Vacuum Phenomenon
• Is a possible sequelae of a traction force to the humerus.
• The traction force results in a pressure reduction in the gleno-
humeral joint. The reduction in joint pressure causes nitrogen
to be released from solution.

41. The Supinator Fat pad Sign
• raised or obliterated as a result of bony injury, particularly to
the radial head.
• It is one of those unreliable soft tissue signs, but is useful as a
guide to potential bony injury, particularly to the radial head.

43. • The elbow fat pad sign (sail sign)

44. • Pronator (Quadratus) Fat Pad Sign
• The dorsal cortex of the distal radius can be seen to deviate
from a smooth curve suggesting a buckle fracture.
-The pronator fat pad is raised suggesting a significant wrist
injury

46. Scaphoid Fat Pad Sign
• Scaphoid fractures are the most common fracture of the carpal
bones, accounting for 70% of carpal bone fractures
The scaphoid fat pad sign refers to a propensity for distortion
or obliteration of the juxtaposed fat stripes in the presence of
a scaphoid fracture.

48. Air in Soft Tissues
• In the context of trauma, this is an important finding because it
indicates that the patient has a open/compound fracture.

50. CASES

51. • 46-year-old man shows
large painless elbow
mass

52. • 34-year-old woman with plantar mass