Table 2 Differentiation of OFD from adamantinoma and fibrous dysplasia

Age (years)

10 ~ 20

OFD-like AD: 10 ~ 20

Classic AD: 30 ~ 40

Dedifferentiated AD: ~20

10 ~ 30 [65]

Nature

Benign

Biphasic

Benign

Common location

(1) Tibia and/or fibula

(2) Arising within the anterior cortex of the diaphyseal [4, 23]

(1) Tibia and/or fibula, followed in the humerus, ulna, and radius

(2) Almost exclusively in the anterior cortex of the diaphysis [62]

(1) Femur and craniofacial bones

(2) Arising within the medullary canal [62]

Clinical presentation

(1) Pain (25%~50%) or painless

(2) Bony deformities (bowing)

(3) Pathologic fractures [4, 23]

(1) Pain and swelling (19%)

(2) A palpable mass

(3) Bony deformities

(4) Pathologic fractures (16%~23%) [66, 67]

(1) Swelling (56.7%)

(2) Pain or tenderness (35.6%)

(3) Pathological fracture (14.4%)

(4) Limping (7.8%)

(5) Maine cafe ́-au-lait spots [65, 68]

Imaging findings

(1) A single or multiple, variably sized, sharply marginated radiolucencies within the cortex of the tibia or fibula, with a surrounding sclerotic rim

(2) An anterior bowing deformity or pathologic fracture may be observed

(3) Soft tissue extension is not present, and intramedullary involvement is unusual

(4) A CT scan and MRI are useful for confirming the intracortical location of the lesion [69]

(1) OFD-like AD: Like OFD

(2) Classic AD and dedifferentiated AD:

 a) Well-demarcated, lobulated, radiolucent lesion within cortical bone, imparting a “soap bubble” appearance

 b) Skip lesions and/or multicentric lesions involving the tibia and/or fibula may be present

 c) May breach the cortex, extending into the medullary cavity or adjacent soft tissues

 d) A CT scan and MRI are useful for documenting multifocality, cortical destruction, and soft tissue extension [69]

(1) The healthy bone is replaced with a more radiolucent, ‘‘ground-glass’’ appearing pattern, with no visible trabecular pattern

(2) The periosteal surface is smooth and nonreactive

(3) Shepherd’s crook deformity [65]

Cross features

(1) exclusively intracortical lesion with a tan-gray, solid cut surface and a gritty consistency

(2) The perioseum is intact, and the surrounding cortical bone is usually sclerotic and thickened

(3) Intramedullary involvement is not typically seen [69]

(1) Solid, well-demarcated, lobulated lesions, with tan-white cut surfaces

(2) Centered within the cortex with variable involvement of the medullary space or extraperiosteal soft tissue [69]

(1) A well-circumscribed, tangrey mass that is dense and variably fibrous with a gritty quality

(2) May be prominent cyst formation

(3) A glassier, blue-tinged appearance may be found in cases with chondroid metaplasia

Microscopic features

(1) A loose storiform, fibrovascular stroma, and woven bony trabeculae with osteoblastic rimming [70]

(2) individual keratin-immunoreactive cells can be detected

(1) OFD-like AD: widely scattered, clearly visible small epithelial nests

(2) Classic AD: a predominant epithelial component, embedded in an inconspicuous OFD-like bland spindled or fibro-osseous stroma. Besides, the epithelial component forms nests, large anastomosing groups, or sheets of monomorphic cells, displaying tubular or glandular structures, basaloid architecture with peripheral palisading of neoplastic cells, squamous differentiation with associated keratinization

(3) Dedifferentiated AD: the abrupt transition of classic AD morphology into a less differentiated, usually pleomorphic sarcoma, losing epithelial differentiation and gaining increased mitoses. Additionally, osteoid or chondroid matrix may be identified in the dedifferentiated foci [71]

(1) It is composed of a bland fibrous stromal proliferation admixed with randomly distributed woven bone

(2) Keratin-immunoreactive stromal cells are never observed

(3) Nodules of benign hyaline cartilage may be present

(4) A key feature is the conspicuous absence of osteoblastic rimming

Immunohistochemical features

Epidermal growth factor receptor was not detected [48]

Epidermal growth factor receptor was detected [48]

Immunohistochemistry serves no purpose in the diagnosis of FD other than to rule out the possibility of a malignant lesion with a pertinent history

Genetic studies

Trisomies of chromosome 7, 8 and 12 [46, 47]

(1) Trisomies of chromosome 7, 8 and 12

(2) extra copies of 19 and/or 21 [46, 47]

(3) KMT2D mutations [72]

(4) P53 mutations [17]

(5) The chromatin remodeling-related gene histone-lysine N-methyltransferase 2D was “recurrently altered” [72]

(1) GNAS mutations [47]

(2) Gs-alpha mutations [47]