Musculoskeletal #18 – Flashcard

27-year-old patient with neurofibromatosis-type 1 (NF-1). Bone lesions found on PET-CT

What are the imaging findings?

Multiple bilateral multiloculated eccentric metaphyseal lucent lesions with thin sclerotic rim

What is the most likely diagnosis?

Multiple non-ossifying fibromas in a patient with NF-1

Teaching points

Very common benign lesion in young adults. Tend to heal or involute. Vast majority asymptomatic. Large lesions may be painful or weaken the cortical predisposing to pathological fracture (rare). Multiple in NF-1

Musculoskeletal #17 – Long Case

2-year-old girl, referring to emergency department after a fall.

What do you see?

Click here to see the answer

– An expansile lytic lesion with ill-defined margins (green arrow) is seen on the diaphysis of fibula.

– Lamellated periosteal reaction (red arrow) suggests an aggressive lesion.

Differential diagnosis of an aggressive lytic lesion in a 2-year-old child includes:
– Osteomyelitis
– Ewing’s sarcoma
– Langerhans cell histiocytosis
– Leukemia/lymphoma

What should be done next?

An MRI scan

Intramedullary hyperintense lesion with extensive surrounding soft tissue and bone marrow edema on coronal STIR image (a) is seen. The lesion is hypointense on T1 WI (b).

Cortical destruction is shown on axial PD image (arrow in c).

Postcontrast coronal (a) and axial fat-suppressed (b) T1-weighted images show extensive enhancement in the lesion and the surrounding soft tissue

Histopathologic examination revealed Langerhans cell histiocytosis.

Langerhans Cell Histiocytosis (LCH)

– LCH is characterised by idiopathic infiltration and accumulation of abnormal histiocytes within various tissues.

– Bone is the most commonly affected tissue in children, with a predilection for axial bones, and femur is the most commonly affected long bone.

– Radiographic appearance of the lesions depends on the site of involvement and the phase of the disease.

Skull: Calvarium is more affected than the skull base, typically seen as single or multiple well-defined lytic lesions on radiography; T1 hypointense, T2 hyperintense with significant enhancement on MRI. Temporal bone is the most common affected part of skull base seen as destructive lesions with a soft tissue component.
Spine: Vertebral bodies are affected with relative sparing of posterior elements. A typical vertebra plana appearance may be encountered with total collapse.
Long bones: Ill-defined lytic lesions with/without cortical destruction are seen usually located at diaphysis or metaphysis. Periosteal reaction may be present. Extensive bone marrow and soft tissue signal changes on MRI may also be helpful in the diagnosis.

Musculoskeletal #16

63-year-old patient with knee pain. What do you see?

Click here to see the answer

IMAGING FINDINGS

Lucent distal femur epiphyseal lesion with thin sclerotic borders and rings-and-archs calcifications, characteristic of chondral matrix

What is the most likely diagnosis?

Enchondroma

CASE 2

Malignant counterpart chondrosarcoma in spinous process of lumbar spinal vertebra

What do you see?

Click here to see the answer

Teaching points

Enchondroma
Characteristic findings: location epiphysis, thin sclerotic borders and rings-and-archs calcifications
It might be indistinguishable from chondrosarcoma on imaging, and pain may raise the latter suspicion
If bone aggressive lysis, striking endosteal scalloping or soft tissue component is present,

Musculoskeletal #15 – Flashcard

This is the third and last case of the musculoskeletal series. Check the first one and second one on this blog.

What do you see on the following images?

Click here to see the answer

Osteoblastoma: Osteoblastoma is histologically similar to osteoid osteoma but they are larger (usually accepted more than 1 cm), often involving the posterior column

Musculoskeletal #12 – Flashcard

43-year-old healthy patient:
– with fibromyalgia
– No other relevant medical history

What do you see on the following images?

Click here to see the answer

IMAGING FINDINGS:

Multiple focal sclerotic bone lesions clustered around joints in both knees and sacroiliac joints

DIAGNOSIS:

Osteopoikilosis

TEACHING POINTS:

Sclerosing bony dysplasia characterized by multiple enostoses
Typically clustered around joints, aligned parallel to trabeculae. Usually 1-3 mm, they can reach up to 20 mm
Rare condition; inherited; asymptomatic; incidental
Important to avoid misdiagnosis with other relevant pathologies such as metastasis

Musculoskeletal #11

68-year-old male:
* Presents with a mass around knee which has been present for seven years and has been enlarging since then

What do you see?

A sclerotic ill-defined soft tissue mass around the knee was present on radiographs.
The mass is located in the soft tissue around the knee with no apparent bone destruction.

Coronal fat-suppressed T2 WI (a) shows a hyperintense lobulated mass which was hypointense on T1 WI (b) and has peripheral heterogeneous enhancement on postcontrast T1 WI (c); cortical bone is preserved.

The mass encircles a pedunculated lesion which continues with cortical and medullary bone (arrows), consistent with an osteochondroma.
Histopathologic diagnosis of the mass is chondrosarcoma.

Osteochondromas

* Osteochondromas are developmental lesions rather than true neoplasms and are often referred to as an osteocartilaginous exostosis (or simply exostosis).
* An osteochondroma is composed of cortical and medullary bone protruding from and continuous with the underlying bone; cortical and medullary continuity between the osteochondroma and parent bone is well depicted on MRI.
* Malignant transformation, almost invariably due to chondrosarcoma arising in the cartilage cap of the lesion, occurs in approximately 1% of solitary osteochondromas.
* Lesions that grow or cause pain after skeletal maturity should be suspected of malignant transformation since osteochondromas only rarely enlarge after this time.

Musculoskeletal #10 – Flashcard

29-year-old long-distance athlete presenting with 3 weeks of sciatica associated with an increase of running training loads

What do you see?

Click here to see the answer

IMAGING FINDINGS:

Unilateral sacral bone edema T2W, STIR hyperintensity associated with hypointense fracture line

DIAGNOSIS:

Fatigue stress fracture

TEACHING POINTS:

The sacrum is a frequent site for stress fractures
They can be related to overload occurring in a healthy bone as in this case, or related to osteoporosis (insufficiency stress fractures) in which cases they tend to be bilateral and “h- shaped”

Musculoskeletal #9 – Flashcard

12-year-old boy, asymptomatic:

Radiograph a

Radiograph b

What do you see?

Lytic lesion on distal fibular metaphysis with well-defined sclerotic borders is seen on both anteroposterior (a) and oblique (b) radiographs

What do you see?

NOF: non ossifying fibroma

– Most common fibrous bone lesion
– Same as fibrous cortical defect but larger version
– If large enough, may cause pathological fractures
– One of DON’T TOUCH lesions

Musculoskeletal #8 – Flash card

What do you see on the following images?

CT scout view

CT soft tissue window

CT bone window

Click here to see the answer

Skull eosinophilic granuloma
Well defined lytic lesion with scalloped edges. It involves both the inner and outer table. Narrow zone of transition, no cortical breakthrough and no soft tissue component.