Age / Sex : 18 / F

Chief complaint: left hip pain after fall down

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(Quiz는 quiz일 뿐이오니 답안은 한개만 보내주시기 바라오며, 복수의 답안을 보내주시는 분은 정답이 포함되어 있더라도 부득이 semi-correct answer로 처리토록 하겠습니다.)

Courtesy: 정선관(Jung Seon Kwan), 원광대병원(Wonkwang University School of Medicine & Hospital)
 

Cystic fibrous dysplasia

Discussion

Findings:

Plain radiograph of both hips shows
a focal osteolytic lesion surrounded by band of sclerosis (geographic type Ia)
in the right femoral neck eccentrically. 

MRI shows a well defined intramedullary lesion having the greater portion
of cystic lesion having bright increased SI on T2WI and the smaller portion of
solid lesion in the distal area of the mass in the right femoral neck.

Differential Diagnosis:

ABC

GCT

Diagnosis:
Cystic fibrous dysplasia

Discussion:

A hazy “ground glass” density is the
most common finding of fibrous dysplasia on plain radiographs. The pathology
usually is typical. However, the classical findings can be modified causing
diagnostic confusion when hemorrhage, myxoid degeneration, secondary aneurysmal
bone cyst formation, nonspecific cystic change supervenes.

Prominent
lysis with rapid expansion of fibrous dysplasia lesion has been described to
result from nonspecific cystic change, secondary aneurysmal bone cyst, or
malignant transformation. So-called cystic fibrous dysplasia is not uncommon in
the skull, facial bones, and ribs, but only sporadically has been reported in
the long bone.

Jaffe and
Schlesinger et al described cases of rapidly enlarging bone tumor caused by
hemorrhagic cystic degeneration in a “fibrodysplastic” lesion. The affected
site was the rib and tibia, respectively. Since then only several cases have
been reported in the long bone..

On MRI two
different signals of fibrous dysplasia lesion and cystic lesion favors the
diagnosis of benign nature of a lesion.

Distinct
phenomenon of cystic change in fibrous dysplasia should not automatically be
interpreted as secondary aneurysmal bone cyst.  Indeed, aneurysmal bone
cyst is not a common complication of fibrous dysplasia. It is common in giant
cell tumor and chondroblastoma but rare in fibrous dysplasia, chondromyxoid
fibroma, nonossifying fibroma, osteoblastoma, and osteosarcoma. Both
nonspecific degenerative cyst and secondary aneurysmal bone cyst can almost
completely obliterate underlying fibrous dysplasia.  

 Open biopsy is seldom necessary to diagnose
fibrous dysplasia but may be indicated to confirm the diagnosis when the
presentation is non-classical. The fact that difficulty in differentiate nonspecific
cyst form secondary aneurysmal bone cyst based on MRI features requires a
biopsy. Surgical treatment is indicated when pain is disturbing, deformity is
disabling, or pathologic fracture supervenes..

References:

1.    
Bahk WJ,
Kang YK, Rhee SK, Chung YG, Lee AH, Bark YH. Cystic fibrous dysplasia in the
long bone. Orthopedics  2007;30:

2.    
DeIure F,
Campanacci L. Clinical and radiographic progression of fibrous dysplasia:
cystic change or sarcoma? Description of a case and review of the literature.
Chir Organi Mov. 1995; 80:85-89.

3.    
Okada K,
Yoshida S, Kumiko O, Sageshma M. Cystic fibrous dysplasia mimicking giant cell
tumor: MRI appearance. Skeletal Radiol. 2000; 29:45-48.

4.    
Simpson AH,
Creasy TS, Williamson DM, Wilson DJ, Spivey JS. Cystic degeneration of fibrous
dysplasia masquerading as sarcoma. J Bone Joint Surg Br. 1989; 71:434-436.