Benign Bone Tumours

Question 1

Osteochondroma

Answer 1

Bony outgrowth on external surface with a cartilaginous cap
Causes local pain, no invasion
Chance of malignancy = very low, 1%

Question 2

Enchondroma

Answer 2

Intramedullary (metaphyseal) cartilaginous tumour caused by failure of normal enchondral ossification of growth plate
Usually appear lucent on imaging but can show patchy mineralisation

Question 3

Unicameral Bone Cyst

Answer 3

Simple bone cyst - single fluid filled cavity (often from physeal growth defect)

Question 4

Aneurysmal Bone Cyst

Answer 4

Multi-cavity cyst filled with blood/serum caused by an arteriovenous malformation
Causes local invasion and cortical destruction (with pain)

Question 5

Giant Cell Tumour

Answer 5

Locally aggressive tumour made of multi-nucleate giant cells

Occurs after fusion of the physis

Question 6

Treatment for most benign bone tumours?

Answer 6

Curettage +/- bone graft +/- stabilisation

Question 7

What can all of these cause?

Answer 7

Pathological fracture

Question 8

What does a giant cell tumour look like on x-ray?

Answer 8

soap bubble

Question 9

Can giant cell tumours metastasise?

Answer 9

5% metastasize to the lung

Question 10

How is giant cell tumour treated?

Answer 10

Intralesional excision with either phenol, bone cement, or liquid nitrogen to destroy the remaining tumour material - reduces risk of recurrence

Question 11

Fibrous Dysplasia

Answer 11

Genetic mutation causes lesions of fibrous tissue and immature bone
Stress fractures occur
Adolescence

Bisphosphonates may reduce pain & pathologic fractures should be stabilised with internal fixation, & cortical bone grafts used to improve strength

Simple intralesional excision alone has a high recurrence rate

Question 12

Where is shepherd’s crook deformity seen?

Answer 12

Extensive involvement of the proximal femur in fibrous dysplasia

Question 13

Fibrous dysplasia:
One bone
Two bones

Answer 13

Monostotic

Polystotic

Question 14

Osteoid Osteoma

Answer 14

Small nidus of immature bone surrounded by an intense sclerotic halo

Occur in adolescence
Most often in proximal femur, diaphysis of long bones, & vertebrae

Pain is worse at night, relieved by NSAIDs

Lesion is seen on X-ray
Bone scan (intense uptake) and CT confirm diagnosis
May resolve spontaneously but some require CT guided radiofrequency ablation/excision

Question 15

Brodie’s abscess

Answer 15

Subabcute osteomyelitis

Presents with a lytic bone lesion

Question 16

Brown tumours

Answer 16

lytic bone tumour associated with hyperparathyroidism