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LEFT ORBITAL BENIGN FIBRO-OSSEUS LESION
Authored By: Joanna Fair and Jerold Wallis, Assoc Prof of Radiology.
Patient: 47 year old female
History: Breast cancer.
Image Size:[small][as-submitted]

Fig. 1
Whole-body bone scan images.

Fig. 2
Spot images from the bone scan.

Fig. 3
Axial CT images through the orbits with bone windows.

Fig. 4
Coronal CT image through the orbits with bone windows and axial CT image through the orbits with soft tissue windows.

Fig. 5
axial T2 FLAIR and pre-contrast T1 MR images

Fig. 6
coronal and axial T1 post-contrast MR images
Image Size:[small][as-submitted]

Findings: 19.8 mCi Tc-99m MDP i.v.

Findings:

There is a focal region of intense radiopharmaceutical uptake in the left superolateral orbit. There is also mildly increased radiopharmaceutical uptake in both shoulders, knees, ankles and feet.


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CT orbits:

Well-defined lytic lesion in the superolateral left orbital wall with associated small extraconal soft tissue mass.


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MRI orbits without and with contrast:

5 x 8 mm, uniformly enhancing soft tissue mass within the left lateral orbital wall which corresponds to lesion seen on bone scintigraphy and computed tomography.







DDx: 1.  Metastatic breast cancer

2.  Benign primary bone tumor (e.g., epidermoid, ossifying fibroma, fibrous dysplasia)

3.  Malignant primary bone tumor
Diagnosis: Benign fibro-osseous lesion of the left superolateral orbital wall.
General Discussion: Full patient history:

47-year-old female with newly diagnosed stage II left breast cancer. She reported no bone pain.  The uptake in the left orbit seen on bone scintigraphy was thought to be more intense than typically seen as a normal variant in this region, and metastasis should be considered. The appearance on the orbital CT was thought to favor a benign condition such as epidermoid; however, given the history of breast cancer, metastatic disease was not excluded. On MRI, the lesion was thought not have to have signal characteristics of a dermoid or epidermoid lesion, and metastasis was not not excluded.

The patient then underwent excisional biopsy.


Pathology:

The lesion consists of fibroconnective tissue with interspersed bone spicules. Foamy histiocytes are also present.  These findings indicate a benign fibro-osseous lesion.  The term 'fibrous dysplasia' is used by some pathologists, and the term 'ossifying fibroma' is used by others, to describe this entity.  No malignancy is seen.

Followup:  The patient had several subsequent bone scans, which showed no additional metastatic lesions, and interval decrease in uptake at the excision site.

Discussion: 

Benign fibro-osseus lesions include ossifying fibroma and fibrous dysplasia.  These entities are often not distinguishable on histopathologic evaluation. 

Ossifying fibromas occur predominantly in women in the 3rd/4th decades.  In the early stage, lesions may appear as solitary, radiolucent, cyst-like masses with minimal or absent internal calcified components.  Later, lesions become radiodense. On MRI, lesions are typically intermediate signal intensity on T1-weighted sequences and hypointense on T2-weighted sequences.  These lesions typically show moderate enhancement following intravenous administration of contrast on T1-weighted sequences.
 
Fibrous dysplasia has several major types.  The pagetoid type is characterized by bone expansion and alternate areas of radiodensity and radiolucency, while the sclerotic type appears as bone expansion with homogeneous radiodensity, often referred to as 'ground-glass' lesions on CT.  The cyst-like type is solitary and round or oval and appears as a well-defined radiolucent image with sclerotic margin; when lamellar, onion peel-like sclerosis appears, it is often referred to as an 'egg-shell lesion' on CT.



References: Papadaki ME, Troulis MJ, Kaban LB, "Management of the Pediatric Maxillofacial Patient,"  Oral and Maxillofacial Surgery Clinics of North America 17(4): 415-434 (2005). 

MacDonald-Jankowski DS, "Fibro-osseous lesions of the face and jaws," Clinical Radiology 59, 11-25 (2004).
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Additional Details:

Case Number: 173604Owner(s): Joanna Fair and Jerold Wallis, Assoc Prof of RadiologyLast Updated: 02-07-2013
Anatomy: Skeletal System   Pathology: Benign Mass, Cyst
Modality: CT, MR, Nuc MedAccess Level: Readable by all users, writable by NucMed Certifiers
Keywords: bsnm, bone scintigraphy, ossifying fibroma, fibro-osseus lesion, fibrous dysplasiaACR: 40000.31390

Case has been viewed 33 times.
Certified by Jerold Wallis on 06-24-2009

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