Fibro-osseous lesions introduction

FIBRO-OSSEOUS LESIONS

INTRODUCTION

• The term ‘FOL’ is a generic designation of a group of bone disorders characterized by the replacement of bone by a benign connective tissue matrix that displays varying degrees of mineralization in the form of woven bone or cementum.

• Group include:

• developmental lesions

• reactive / dysplastic lesions

• neoplastic lesions

Importance of Specific Diagnosis

• The histopathology of all FOL is identical, although they range widely in clinical behavior.

• More specific diagnosis is important because the treatment of these pathoses varies from none to surgical recontouring to complete removal.

CLASSIFICATION

• FOL of medullary bone origin

• FD

• Fibro osteoma

• Cherubism

• Juvenile OF

• Giant cell tumor

• ABC

• Jaw lesions in hyperparathyroidism

• Paget’s disease

WHO classification of Odontogenic tumors (2nd ed, 1992)

• (a) Fibrous dysplasia

• (b) Cemento – ossifying fibroma

• - Spectrum of COF: CF-COF-OF

• - Juvenile Ossifying Fibroma

• WHO type

• Psammous type

• (c) Cemento-osseous dysplasia

• -PCOD

• -Focal COD

• -Florid COD

• -Familial gigantiform cementoma.

Modified WHO classification (Speight and Carlos)

• Fibrous dysplasia

• Monostotic

• Polyostotic

• Craniofacial

FIBROUS DYSPLASIA

• Developmental or hamartomatous condition

• Unknown etiology

• Characterized by proliferation of cellular fibrous connective tissue mixed with bony trabeculae

• Sporadic condition, resulting from post zygotic mutation in GNAS– 1 gene

• Clinical severity depends on the point of time during embryonic, fetal or post natal life at which mutation of GNAS – 1 occurs

Clinical Features

• Monostotic fibrous dysplasia

• Limited to single bone

• 80 – 85% of all cases

• Jaws among most common sites

• Diagnosed during second decade

• No sex predilection

• Painless swelling – most common feature.

• Slow growth, become static with skeletal growth completion

Craniofacial fibrous dysplasia

• Craniofacial fibrous dysplasia

• Peculiar form affecting skull bones

• Not restricted to single bone, but confined to single anatomic site.

• Primarily affect maxillae, but may cross sutures into sphenoid, zygoma, frontonasal bones and base of skull.

Polyostotic FD

• Polyostotic FD

• Involvement of two or more bones other than craniofacial bones

• Number of bones – a few to 75% of skeleton

• With café au lait (coffee with milk) pigmentation, Jaffe – Lichtenstein syndrome

• With café au lait pigmentations and multiple endocrinopathies – sexual precocity, pituitary adenoma or hyperthyroidism, McCune – Albright syndrome

May present with facial asymmetry

• May present with facial asymmetry

• Clinical features usually dominated by symptoms related to long bone lesions – Pathologic fractures

• Length discrepancy due to involvement of upper portion of femur (hockey stick deformity)

• Café au lait pigmentation – generally unilateral tan macules on the trunk and thighs.

• - May be congenital

• - Oral cavity can be involved

• - Margin typically irregular (Coastline of Maine)

Radiographic Features

• Site – Most often involves maxilla

• Posterior aspect. Unilateral

• Periphery ill defined. Gradual blending

• Internal structure.

• Variation pronounced is maxilla

• More uniform in mandible

Radiolucent

• Radiolucent

• Mixed radiolucent-radiopaque

• Heterogenous pattern

• Orange peel – pathognomonic

• Ground glass

• Radiopaque – cottonwool or diffuse

Effect on surrounding structures

• Effect on surrounding structures

• Thinning of cortex

• Displacement of antral walls

• Loss of lamina dura

• Displacement of teeth

• Interference with normal eruption

• Inferior alveolar canal – displaced superiorly / inferiorly

• Superior displacement – unique to FD.

CT

• To define extent of involvement of cranial base.

• 34 – 513 HU

• Heterogeneous pattern of CT densities associated with scattered or confluent islands of bone formation

MRI

• Intermediate signal on T1 weighted and proton weighted images

• Heterogenous hypointense signal of T2 weighted scan

• Moderate to significant contrast enhancement after i.v. Gd contrast infusion.

Management and Prognosis

• Small lesions can be resected entirely

• Most lesion stabilize with skeletal maturation

• Surgical recontouring after skeletal maturation

• Osteosarcoma-especially in those who received radiation.