Bone Cysts & Tumor-like Bone Pathologies Flashcards
What are 2 alternative names for a simple bone cyst?
- Unicameral bone cyst
- Solitary bone cyst
What causes a simple bone cyst?
disturbance of bone growth following trauma
What age group is primarily affected by simple bone cysts?
<20 years
What is the preferential location of simple bone cysts?
proximal metaphysis
- humerus
- femur
- tibia
Describe the pathogenesis of a simple bone cyst
- trauma –> hematoma forms & resolves
- formation of fibrous lining
- fibrous tissue pulls serous fluid into lesion
- fluid pressure leads to bone resorption
- some reactive bone formation (solid)
- produces lytic lesion with thin, well-defined margin and sclerotic border
A simple bone cyst occurs over the course of ____
months
What pattern of destruction is seen in a simple bone cyst?
geographic lytic
A simple bone cyst has a ____ zone of transition
short/narrow
How does the cortical bone appear in a simple bone cyst?
thinning of cortex due to resorption of bone, may lead to pathologic fractures
Why is a simple bone cyst referred to as a “migrating tumor”?
Lesion tends to develop in metaphysis, and can go into diaphysis with age
(NOT a neoplasia)
Is a simple bone cyst a true cyst? Why or why not?
- not a true cyst because there is no distinct cell lining/membrane (which would completely separate it from surrounding tissues)
- has a fibrous lining that allows serous fluid in
What type of cells are found in a simple bone cyst?
- osteoclastic giant cells
- macrophages
- chronic inflammatory cells
- osteoclasts in advancing area of cyst
What type of periosteal reaction may be present in a simple bone cyst?
solid (non-aggressive)
How would a patient present clinically with a simple bone cyst?
- asymptomatic
- incidental finding, usually due to patho. Fx
What are the radiographic characteristics of a simple bone cyst?
- unilocular radiolucent lesion with sclerotic border
- “fallen fragment” sign
- usually centrally located
What is the treatment for a simple bone cyst?
- intralesional corticosteroids
- curettage (scoop out) and bone grafting (pack with bone chips)
- tends to recur
How is a simple bone cyst prevented from recurring?
inject with phenol to kill fibrous lining
What is an aneurysmal bone cyst?
multiloculated lytic lesion with septa composed of fibrous tissue and reactive bone
What age group is primarily affected by aneurysmal bone cysts?
<20 years
What is the preferential location of aneurysmal bone cysts?
80% occur in metaphyseal region of long bones & in the spine
What parts of the spine do aneurysmal bone cysts prefer?
posterior elements:
- articular processes
- pedicles
- lamina
- SPs
What is a primary aneurysmal bone cyst?
(genetic) USP6 overexpression, which leads to ^proteases and transcription factors that upregulate cystic resorption of bone
What is a secondary aneurysmal bone cyst?
develop with other primary tumors
eg. giant cell tumor, osteosarcoma
What does multiloculated mean?
multiple chambers
Aneurysmal bone cysts are filled with ____
blood
Simple bone cysts are filled with ____
serous fluid
What does the appearance of an aneurysmal bone cyst resemble?
“soap bubble” appearance or sponge filled with blood and blood clots
Aneurysmal bone cysts grow (rapidly/slowly)
rapidly
Simple bone cysts grow (rapidly/slowly)
slowly
Are aneurysmal bone cysts typically central or eccentric?
can be either
Are simple bone cysts typically central or eccentric?
central
What are the radiographic characteristics of aneurismal bone cysts?
- expansile
- intact periosteum & cortex, with thinning of cortex (balloon-like)
- multilocular radiolucent lesion
What pattern of destruction occurs in an aneurysmal bone cyst?
geographic lytic
An aneurysmal bone cyst has a ____ zone of transition
short/narrow
What does expansile mean?
enlarged bone
How will a patient with an aneurysmal bone cyst present clinically?
- pain
- swelling
- cyst may blow out and cause local hemorrhage
- patho. Fx (rare)
- possible neurological deficits
Why would a patient with an aneurysmal bone cyst present with neurological deficits?
central canal stenosis when in posterior spinal elements
(this is odd in young ppl!!!)
What is the treatment for an aneurysmal bone cyst?
- curettage and bone grafting
- variable recurrence rate
Which is more likely to be removed:
simple bone cyst // aneurysmal bone cyst
aneurysmal bone cyst due to severe pain
What are the 3 categories of fibrous cortical defect?
- fibrous cortical defect
- non-ossifying fibroma
- fibrous xanthoma
How are the categories of fibrous cortical defect differentiated?
age
(all appear the same histologically, just written about at different times & ages)
What is the term for a fibrous cortical defect that occurs in patients younger than 8 years old?
fibrous cortical defect
What is the term for a fibrous cortical defect that occurs in patients ages 8-19 years?
non-ossifying fibroma
What is the term for a fibrous cortical defect that occurs in patients 20 years and older?
fibrous xanthoma
What is the preferential location of fibrous cortical defect?
- metaphyseal region
- tibia or femur
How would a patient with fibrous cortical defect present clinically?
- usually asymptomatic
- pathologic fracture (thin cortex) -> pain
- may be associated with neurofibromatosis type 1 & Jaffe-Campanacci syndrome
At what point is a patient with fibrous cortical defect at increased risk of pathologic fracture?
When tumor occupies at least 50% of diameter of bone
An 18-year-old patient presenting with multiple non-ossifying fibromas (NOFs) and cafe au lait spots may have what associated condition?
Jaffe-Campanacci syndrome
(associated w/ fibrous cortical defect)
If a patient has multiple fibrous cortical defects, non-ossifying fibromas, or fibrous xanthomas, what 2 conditions might you be concerned about?
- neurofibromatosis type 1
- Jaffe-Campanacci syndrome
What are the radiographic characteristics of fibrous cortical defect?
- cortical location
- eccentric
- geographic lytic
- scalloped margin
- radiolucent lesion with sclerotic border
What periosteal reaction is observed in fibrous cortical defect?
none
Fibrous cortical defect has a ____ zone of transition
short/narrow
What matrix calcification is observed in fibrous cortical defect?
none (purely lytic)
Is there any soft tissue mass involved with fibrous cortical defect? How could you tell?
no
- no mass extending beyond bone
- no (aggressive) periosteal reaction
- no displacement of fascial planes
What is the treatment for fibrous cortical defect?
- spontaneous resolution (no recurrence) -> replaced by normal bone
- curettage & bone grafting (for expanded or symptomatic lesions)
- fracture repair
What age group is primarily affected by fibrous dysplasia?
children/young adults
(usually <10 yrs)
What is the etiology of fibrous dysplasia?
- mutation of GNAS1 gene
- abnormal cellular development
What are the 3 forms of fibrous dysplasia? Which is most common?
- monostotic (MC)
- polyostotic
- McCune-Albright syndrome
The term “fibrous dysplasia” is referring to which form?
monostotic
What is fibrous dysplasia?
failure to form mature lamellar bone in the lesion, resulting in fibrous replacement of bony stroma
How does a fibrous dysplasia lesion begin?
focal, slowly expanding lesion
What does a lesion of fibrous dysplasia consist of?
- fibroblasts
- collagen
- irregular trabeculae
- cystic degeneration + hemorrhage
How common is malignant transformation of fibrous dysplasia, and what would it transform to?
<1% of cases
- osteosarcoma
- chondrosarcoma
- fibrosarcoma
What are the radiographic characteristics of fibrous dysplasia?
- geographic lytic lesions (well-defined borders, thin cortex)
- expansile
- bony deformation (Sheppard’s crook)
- ground glass matrix (uniform density)
What is the most common benign tumor of the rib?
fibrous dysplasia
Fibrous dysplasia has a ____ zone of transition
short/narrow
What age group is primarily affected by monostotic fibrous dysplasia?
10-30 years old
How would a patient with monostotic fibrous dysplasia present clinically?
- asymptomatic
- patho Fx (incidental finding)
- bone enlargement or deformation
- possible altered gait biomechanics
What are the most common locations of monostotic fibrous dysplasia?
- ribs
- femur
- tibia
- facial bones
What populations are primarily affected by polyostotic fibrous dysplasia?
- usually observed in childhood
- may be quiescent in puberty
- lesion growth may increase with pregnancy
How would a patient with polyostotic fibrous dysplasia present clinically?
- > 50% skeleton effected
- bone deformities (size & shape)
- limb length discrepancies
- spine alignment issues
- patho Fx
- Mazabraud syndrome
What is a Sheppard’s crook deformity?
excessive curvature of proximal femur seen in fibrous dysplasia due to bone softening
(bowing deformity of hips)
What is Mazabraud syndrome?
Soft tissue myxomas (benign mesenchymal tumors)
What is the preferential location of polyostotic fibrous dysplasia?
- any bone
- can be unilateral or monomelic
What does monomelic mean?
Affecting 1 limb
What matrix calcification is seen in polyostotic fibrous dysplasia?
ground glass
What form of fibrous dysplasia is exclusive to females?
McCune-Albright syndrome
What is McCune-Albright syndrome?
Polyostotic fibrous dysplasia + endocrine abnormality
What endocrine dysfunctions may present with McCune-Albright syndrome?
- acromegaly
- Cushing syndrome
- hyperthyroidism
- vit D resistant rickets
How does precocious puberty present in females?
- Premature onset of menstrual cycle (~age 8)
- Premature closure of growth plates —> shorter stature
How would a patient with McCune-Albright syndrome present clinically?
- asymptomatic
- patho Fx (incidental finding)
- bone enlargement or deformation
- cafe au lait spots on skin with “coast of Maine” borders
What is the treatment for Fibrous Dysplasia?
- depends on monostotic vs polyostotic
- curettage
- fracture repair
- prevent deformities (bracing)
- manage endocrine hormones
A 5 year old has pain after a fall. In the proximal humerus, there is a geographic lytic lesion with a pathologic fracture, and a cortical fragment inside the lesion. What is your diagnosis?
Simple bone cyst
- <20yrs
- incidental finding (patho Fx)
- prefers proximal metaphysis (humerus)
- geographic lytic
- fallen fragment sign
An 18 year old patient was x-rayed because they twisted their ankle. There is a geographic lytic lesion in the distal tibia. It has a narrow zone of transition, no periosteal reaction, no matrix calcification, and no soft tissue mass. The lesion occupies 10% of the diameter of the tibia. If left alone, what will the likely outcome be?
Spontaneous resolution
(Non-ossifying fibroma)
What lesion MUST be eccentric and cortically based?
fibrous cortical defect/non-ossifying fibroma/fibrous xanthoma
Precocious puberty is associated with ____
Fibrous dysplasia (McCune-Albright Syndrome)
Which lesion does NOT have a geographic lytic appearance on radiograph?
A) aneurysmal bone cyst
B) paget disease
C) enchondroma
D) non-ossifying fibroma
Paget disease
What age group is primarily affected by fibrous cortical defect?
<8 years
What age group is primarily affected by non-ossifying fibroma?
8-19 years
What age group is primarily affected by fibrous xanthoma?
20+ years
