Fibrous Lesions

Question 1

What is Fibrous Dysplasia?

Answer 1

Failure of normal bone elements to differentiate into mature bone

Question 2

What percentage of Fibrous Dysplasia cases are Monostotic?

Answer 2

0.7

Question 3

What percentage of Fibrous Dysplasia cases are Polyostotic?

Answer 3

0.3

Question 4

What is the histology of Fibrous Dysplasia?

Answer 4

Local intramedullary fibrous lesion with curved woven bone ‘Chinese letters’, no osteoblast rimming

Question 5

What is the mutation associated with Fibrous Dysplasia?

Answer 5

GNAS-1 mutation

Question 6

What syndrome is associated with Fibrous Dysplasia?

Answer 6

McCune-Albright Syndrome

Question 7

What are the characteristics of McCune-Albright Syndrome?

Answer 7

Triad → Polyostotic fibrous dysplasia, café-au-lait spots, endocrine dysfunction

Question 8

What is Fibrous Cortical Defect (FCD)?

Answer 8

Benign fibrous lesion that starts in the cortex of the metaphysis of long bones

Question 9

What happens when Fibrous Cortical Defect expands?

Answer 9

It can expand into the medullary cavity and be called a non-ossifying fibroma

Question 10

What is the size of a Fibrous Cortical Defect (FCD)?

Answer 10

< 0.5 cm, cortical

Question 11

What is a Non-Ossifying Fibroma (NOF)?

Answer 11

A larger fibrous lesion that expands into the medullary cavity and has a risk of pathologic fracture