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FRCR 2A (Crack The FRCR 2A) > 2. MSK (Bone Tumours) > Flashcards

2. MSK (Bone Tumours) Flashcards

Bone Tumours

1
Q

Commonest primary osseous malignancies (3)

A

1) Myeloma/plasmacytoma (27%)
2) Osteosarcoma (20%)
3) Chondrosarcoma (20%)

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2
Q

Osteosarcoma - Subtypes

A

Conventional intramedullary (85%)
Paraosteal (4%)
Periosteal (1%)
Telangectatic (rare)

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3
Q

Conventional Intramedullary Osteosarcoma (general info)

A

Higher grade than surface subtypes
Typically younger pt (10-20)
Typically femur (40%) and proximal tibia (15%)

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4
Q

Periosteal reactions (buzzwords)

A

Sunburst - Agressive periosteal reaction, looks like sunburst
Codman triangle - New periosteum doesn’t have time to completely ossify, so only raised edge ossifies
Lamellated (onion skin) - multiple layers of parallel periosteum

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5
Q

High yield trivia (osteosarcoma)

A

Osteosarcoma met to lung is classic cause of occult pneumothorax
Reverse zoning - denser matrix in centre, less dense periphery

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6
Q

Risk factors for pathologic fractures (3)

A

1 - Lytic lesions
2 - Lesions >3cm in size
3 - Lesions involving >50% of cortex

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7
Q

Parosteal osteosarcoma (general) (5)

A

Low grade, bulky, parosteal bone formation.
BIG tumours.
Early adult/middle age.
Commonly posterior distal femur. 90% metaphysis.
String sign: radiolucent line separating bulky tumour from cortex.

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8
Q

Periosteal osteosarcoma (5)

A

Worse prognosis than parosteal, better than conventional intramedullary.
15-25YO.
More commonly diaphyseal.
Classically medial distal femur.
No marrow extension unlike parosteal (50%).

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9
Q

Telangectatic Osteosarcoma (general) (4)

A

15% have narrow zone of transition.
Fluid-fluid level on MRI is classic.
T1 bright (methaemoglobin).
Tumour nodularity and enhancement differentiates from CGT and ABC

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10
Q

Fluid-fluid levels DDx (3)

A

Telangectatic Osteosarcoma
Aneurysmal Bone Cyst
Giant Cell Tumour

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11
Q

Chondrosarcoma (4)

A

Usually older adults (M>F)
Flat bones, proximal tubular bones, limb girdles.
Central (intramedullary) or peripheral (end of osteochondroma)
Usually low grade

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12
Q

Chondroblastoma in adult

A

Clear cell chondrosarcoma

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13
Q

Ewings sarcoma (3)

A

Permeative lesion in the diaphysis of child
Usually mets bone to bone
Mimic osteosarcoma due to marked sclerosis (occurs in bone only, not soft tissue like osteosarcoma)

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14
Q

Chordoma (3)

A

Age 30-60, younger in clivus, older in sacrum
Very T2 bright
Sacrum > Clivus > Vertebral body

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15
Q

Chordoma trivia (3)

A

Commonest primary malignancy of spine or sacrum
Most common spinal location is C2
Almost always midline

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16
Q

Fibrosarcoma (4)

A

Can be primary or secondary (Pagets, infarct etc).
Lytic malignant tumours that DONT produce osteoid or chondroid matric.
Almost always lytic, may be permeative or moth eaten
NOT T2 bright (most tumours are)

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17
Q

MFH (5)

A

Malignant Fibrous Histiocytoma (Now called Pleomorphic Undifferentiated Sarcoma (PUS)).
More common than fibrosarcomas, most common soft tissue sarcoma in adults.
Look radiologically similar to fibrosarcoma.
Bone infarcts can turn into MFH (Buzzword: Sarcomatous transformation of infarct)

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18
Q

Synovial sarcoma - features (3)

A

Commonest in lower extremities of patients aged 20-40.
Close to (but not in) joint.
10% get secondary invasion into the joint (for multiple choice, they “never involve joint)

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19
Q

Synovial sarcoma - imaging (3)

A

Triple sign
- High, medium and low signal in the same mass on T2 (usually knee)
Bowl of grapes
- Bunch of fluid-fluid levels in a mass (probably knee)
Plain film
- Soft tissue component with calcifications, least likely way to show it.

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20
Q

Synovial sarcoma - trivia (6)

A

Most sarcomas don’t attach bones, these can.
Most present as painless mass, these hurt.
Soft tissue calcifications + bone erosions are highly suggestive.
Show growing & small, often lead people to call them benign.
90% have translocation of X-18.
Most common malignancy in teens/young adults of foot, ankle and lower extremity

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21
Q

Ball like tumour in extremity of young adult

A

Synovial sarcoma

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22
Q

Liposarcoma (4)

A

2nd commonest soft tissue sarcoma.
Common in middle aged, commonly in retroperitoneum (can also happen in extremities).
Most common type is well differentiated (least aggressive).
Fatty mass in the retroperitoneum = Liposarcoma

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23
Q

Liposarcoma vs lipoma (3)

A

Imhomogenous attenuation - soft tissues masses in the fat
Infiltration of adjacent structures
Deep and big

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24
Q

Myxoid liposarcoma (3)

A

Commonest liposarcoma in <20yo.
Can be T2 bright but T1 dark, not a cyst.
Needs gadolinium imaging

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25
Q

Treeatment of agressive lesions (4)

A

Osteosarcoma - Chemo (to kill micro mets) then wide excision.
Ewings: Chemi and Radiation, then wide excision.
Chondrosarcoma: Usually just wide excision (low grade, main concern is local recurrence)
Giant Cell Tumour: Usually requires arthroplasty as it extends to articular surface.

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26
Q

Myositis ossificans (3)

A

Circumferencial calcifications with lucent centre.
Can look scare on MRI if imaged early due to oedema and avid enhnacement.
Benign, don’t biopsy

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27
Q

Avulsion injury (2)

A

Typically near pelvis, can have aggressive periosteal reaction.
Benign, don’t biopsy.

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28
Q

Cortical desmoid (3)

A

Classically on posterior medial epicondyle of distal femur.
Can be hot on bone scan.
Benign, don’t biopsy.

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29
Q

Synovial Herniation Pit (4)

A

Aka pitt’s pit.
Characteristic location in femoral neck.
Lytic appearing lesion.
Benign, don’t biopsy

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30
Q

Bone biopsy (5)

A

D/W ortho to avoid contaminating parts not involved by tumour.
Pelvis: Avoid crossing gluteal muscles (may be needed for reconstruction).
Knee: Avoid joint space via crossing suprapatellar bursa or other communicating bursae.
Avoid crossing Quads tendon unless involved.
Shoulder: Avoid posterior 2/3 (axillary nerve courses post to anterior, therefore posterior resection will denervate antererior third)

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31
Q

Cystic bone lesions - DDx (8)

A

<30: EG (eosinophilic granuloma), ABC, NOF, Chondroblastoma, Solitary Bone Cysts
>40: Mets, Myeloma
Any age: Infection

32
Q

Epiphyseal lesions - DDx (5)

A

ABC (usually metaphyseal, but after growth plate closes it can extend into epiphysis)
Infection
Giant Cell
Chondroblastoma

Beware of epiphyseal equivalents (carpals, patella, greater trochanter and calcaneus)

33
Q

Malignant epiphyseal lesion (2)

A

Clear Cell Chondrosarcoma
- Slow growing, varied appearance (lytic, calcified, lobulated, ill defined)

34
Q

Metaphyseal lesions DDx (3)

A

Fastest growing area with best blood supply.
Increased predilection for mets and infection.
Most of the cystic bone lesions can occur here

35
Q

Diaphyseal lesions DDx

A

Most things can occur here, like the metaphysis, only less often

36
Q

Fibrous dysplasia features (5)

A

Skeletal developmental anomaly of osteoblasts (failure of normal maturation and differentiation).
Can occur at any age
- Monoostotic in 20s and 30s, polyostotic in <10.
Likes ribs and long bones.
Can occur in the pelvis, where it also affects ipsilateral femur (Shepherd Crook Deformity).
Multiple ones like skull and face (Lion-like faces)

37
Q

Fibrous dysplasia - imaging (4)

A

Very variable appearance, buzzword is groundglass.
Buzzword: long lesion in long bone
Textbook: Lytic lesion with hazy matrix.
No periosteal reaction or pain.

38
Q

McCune Albright vs Mazabraud syndrome (5)

A

Both Polyostotic Fibrous Dysplasia.
Girls vs Middle aged women
Cafe-au-lait spots vs Soft tissue myxomas.
Precocious puberty vs Increased risk of osseous malignant transformation.

39
Q

Adamantinoma (2)

A

Tibial lesion that resembles fibrous dysplasia (mixed lytic and sclerotic).
Potentially malignant.

40
Q

Enchondroma (5)

A

Tumour of medullary cavity composed of hyaline cartilage.
Lytic lesion with irregularly speckled calcification of chondroid matrix, classically described as arcs and rings.
Chondroid matrix is not found in the fingers or toes (high yield).
Enchondroma is most common cystic lesion of hands and feet.
No periostitis - like fibrous dysplasia

41
Q

Enchondroma vs Low grade chondrosarcoma

A

History of pain suggests chondrosarcoma

42
Q

Ollier’s syndrome vs Maffucci syndrome (2)

A

Only enchondromas
vs
Enchondromas and Haemangiomas, with malignant potential (20% turn into chondrosarcoma, other cancers such as GI and ovarian)

43
Q

Eosinophilic granuloma (7)

A

Seen usually in <30yo.
Can be solitary (usually) or multiple.
3 classic appearances
- Vertebra plana in a child
- Skull with lucent “beveled edge” lesions in a child
- “floating tooth” with lytic lesion in alveolar ridge
Varied appearance, can be lytic or blastic, with or without sclerotic border, with or without periosteal response.
Can have osseous sequestrum.

44
Q

DDx for Vertebral Plana (5)

A

MELT
Mets/myeloma
Eosinophilic Granuloma
Lymphoma
Trauma/TB

45
Q

DDx for Osseous Sequestrum (5)

A

Osteomyelitis
Lymphoma
Fibrosarcoma
EG
Osteoid Osteoma can mimic a sequestrum

46
Q

Giant cell tumour (5)

A

Criteria
- Physis MUST be closed
- Non-sclerotic border
- Abuts the articular surface
Considered “quasi-malignant” because they can be locally invasice and 5% have pulmonary mets.
These are curable and should be resected with wide margins

47
Q

Giant cell tumour - trivia (5)

A

Most common in the knee - abutting articular surface
Most common in age 20-30 (physis must be closed)
Associated with ABCs
Quasi-malignant - 5% have lung mets
Fluid levels on MRI

48
Q

Non-ossifying fibroma (6)

A

Common, seen in children
Will spontaneously regress (becoming more sclerotic before disappearing).
Rare in children not yet walking.
Tend to occur around the knee
Classically “eccentric with thin, sclerotic border” (GCTs don’t have sclerotic border).
If <2cm, called fibrous cortical defects (Fibroxanthoma is term for both)

49
Q

Osteoid osteoma (5)

A

Buzzwords
- Pain at night, relieved by aspirin
- Large amount of oedema for size of lesion
Seen in meta/diaphysis of long bones and posterior elements of spine, most commonly lumbar spine.
Associated with painful scoliosis with convexity pointed away from lesion.
Can be treated with percutaneous radiofrequency ablation (as long as not within 1cm of nerve or other vital structure, usually avoided in hands, spine and pregnant patients)

50
Q

Associations of osteoid osteoma (4)

A

Painful scoliosis
Growth deformity - increased length and girth of long bones
Synovitis: can be intra-articular, leading to early arthritis
Arthritis - due to primary synovitis or secondary from altered joint mechanics

51
Q

Osteoblastoma (3)

A

Osteoid osteoma >2cm
Seen in <30YO
Usually in posterior elements or long bones (35%), usually diaphyseal (75%)

52
Q

Metastatic disease (4)

A

Differential for anyone over 40 with lytic lesions.
Renal cancer mets are ALWAYS lytic.
Classic blastic lesions - prostate, carcinoid, medulloblastoma
Classic lytic lesions - renal, thryoid

53
Q

Multiple myeloma - features (3)

A

Plasma cell proliferation increases surounding osteolytic activity.
Usually older patients (40s-80s)
Plasmacytomas can precede clinical or haematologic evidence by 3 years

54
Q

Multiple myeloma - imaging (5)

A

Usually discrete margins, can be solitary or multiple.
Vertbral body destruction with sparing of posterior elements is classic.
Bone scan often negative.
Skeletal survey is better, MRI is most sensitive.
MM can manifest as diffuse osteopenia

55
Q

Plasmacytoma (4)

A

Discrete, solitary mass of neoplastic monoclonal plasma cells in bone or soft tissue.
Associated with latent systemic disease in most cses.
Can be considered singular counterpart of multiple myeloma.
Geographic lytic area, sometimes with expansile remodelling
Mini Brain Appearance - plasmacytoma in vertebral body

56
Q

POEMS (7)

A

Myeloma with sclerotic mets
Rare medical syndrome with plasma cell proliferation (myeloma) with neuropathy and organomegaly
- Polyneuropathy
- Organomegaly
- Endocrinopathy
- Monoclonal Gammopathy
- Skin changes

57
Q

Aneurysmal Bone Cyst (6)

A

Aneurysmal lesions of bone with thin walled, blood filled spaces (fluid-fluid level on MRI).
Usually <30YO.
May develop them following trauma.
Location: Tibia > vertebrae > femur > humerus
Primary or secondary, associated with another tumour (classicallyl GCT)
Commonly associated with other benign lesions

58
Q

Lucent lesion in posterior elements - DDx (3)

A

Osteoblastoma
ABC
TB

59
Q

Solitary (Unicameral) bone cyst (6)

A

Usually <30
More common in tubular bones (usually humerus or femur)
“Always located centrally”
Imaging
- 1) Fracture through it in the humerus w/fallen fragment sign
- 2) Lucent lesion in the calcaneus (probably w/fallen fragment sign)
Fallen fragment sign: Bone fragment in the dependent portion of lucent bone lesion is pathognomonic of solitary bone cyst.

60
Q

Brown tumour (4)

A

Associated with hyperparathyroidism.
Brown tumour represents localised accumulation of giant cells and fibrous tissues.
Lytic or sclerotic lesions with other findings of hyperparathyroidism (subperiosteal bone resorption, classically on side of finger, edge of clavicle or under a rib)
They resorb and can become totally sclerotic/healed when hyperparathyroid is treated.

61
Q

Chondroblastoma (4)

A

Seen in kids
1) Epiphysis of tibia on teenager or 2) in an epiphyseal equivalent.
Epiphyseal equivalents:
- Patella, Calcaneus, Carpal bones
- Apophyses (Greater and lesser trochanter, tuberosities, etc)

62
Q

Chondroblastoma - features (8)

A

Thin sclerotic rim.
Extension across physeal plate
Periostitis
Location: Femur > humerus > tibia.
May show marrow oedema and soft tissue oedema on MRI.
One of few bony lesions often NOT T2 bright.
Tend to reoccur afte rresection.
Chondroblastomas of the hip tend to favor the GT more than femoral epiphysis.

63
Q

Chondromyxoid fibroma (4)

A

Least common benign cartilage lesion.
Usually <30yo.
Osteolytic, elongated in shape, eccentrically located, metaphyseal lesion with cortical expansion and bit like confugiration.
Sort of looks like NOF

64
Q

Greater trochanter - DDX (3)

A

It’s an epiphyseal equivalent and the chondroblastomas prefer it to the femoral epiphysis.
ABC, Infection and GCT happen here too
Avulsions of the gluteus (minimus and medius)

65
Q

Lesser trochanter - DDx

A

Avulsion fracture without significant clinical Hx should make you think of pathologic fracture

66
Q

Intertrichanteric region DDx (3)

A

Lipoma,
solitary bone cyst and
monoostotic fibrous dyslplasia

67
Q

Calcaneal lesions - DDx (8)

A

Solitary bone cyst
- Sharp edges, thick sclerotic edge with multiloculated appearance is helpful.
- Fallen fragment will be more in the bottom if shown (but fractures of the calcaneus are less common)
Pseudocyst
- Variation in normal trabecular pattern, creates a central triangular radiolucent area
- Persistence of thin trabeculae and visible nutrient foramen, along with classic location, are helpful signs of this
Interosseous lipoma
- Fat density on CT or MRI
- Central fragment, stuck in the middle of the fat
- Calcification & fat necrosis occurs about 50% in the real world
Epiphyseal equivalent
- therefore ABC, infection, GCT and Chondroblastoma can occur here, tend to be more posterior calcaneus
Geode can mimim cystic lesion in older people with arthritis

68
Q

No periostitis or pain - DDx (4)

A

Fibrous dysplasia
Enchondroma
NF
Solitary Bone Cyst (unless fractured)

69
Q

Multiple lesions DDx (5)

A

Fibrous dysplasia
EG
Enchondroma
Mets/myeloma
Hyperparathyroidism

70
Q

Liposclerosing myxofibroma (3)

A

Characteristic location: Intertrochanteric region of femur
Geographic lytic lesion with sclerotic margin
10% undergo malignant degeneration so needs following

71
Q

Osteochondroma (5)

A

Most common benign tumour.
Can be radiation induced, making them the only benign skeletal tumour associated with radiation.
Small risk of malignant transformation (cartilage cap >1.5cm is concerning)
Point away from joint
Bone marrow flows freely into the lesion

72
Q

Multiple hereditary exostosis (2)

A

AD, multiple osteochondromas.
Increased risk of malignant transformation.

73
Q

Trevor disease (Dysplasia Epiphysealis Hemimelica (DEH)) (3)

A

Osteochondromas develop in epiphyses causing significant joint deformity (commonest in ankel and knee).
Can see in young children.
Osteochondroma looks like irregular mass.
Tend to be treated with surgical excision.

74
Q

Supracondylar spur (4)

A

aka avian spur.
Normal variant.
Osseous process, usually does nothing but can compress the median nerve if the ligament of Struthers smashes it.
Points towards joint (unlike osteochondroma)

75
Q

Periosteal chondroma (3)

A

aka Juxta-cortical chondroma
Lesion in finger of child
Rare, of cartilaginous origin,
Saucerization of the adjacent cortex with sclerotic periosteal reaction can be seen.

76
Q

Osteofibrous dysplasia (3)

A

Benign lesion in tibia or fibula in children.
looks like NOF but centered in the anterior tibia
Associated anterior tibial bowing.
Can occur with adamantinoma, 2 cannot be differentiated with imaging

FRCR 2A (Crack The FRCR 2A) (55 decks)

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