Fibrous dysplasia is a benign fibro-osseous lesion caused by a mutation in the GNAS1 gene. It involves the replacement of normal bone by fibrous tissue and irregularly shaped trabeculae of woven bone. Common sites are the craniofacial bones. Cherubism is a related condition restricted to the jaws, caused by SH3BP2 mutations. Ossifying fibroma is a benign neoplasm composed of cellular fibrous tissue with variably sized calcified deposits. Differential diagnosis includes Paget's disease, osteosarcoma, and other fibro-osseous lesions.

1. Dr.Roohia

2. 

3. 
 FD is derived from osteoprogenitor, fibroblastlike Cells
 Activating, somatic mutation in the GNAS1 gene found on
chromosome 20q13.
 2 distinct missense mutations in the alpha subunit of a G
stimulatory protein have been identified that account for disease
processes.
activation of adenylyl cyclase
cyclic adenosine monophosphate.
alteration in the transcription and expression of several downstream
target genes, including c-fos, a proto-oncogene
FD

4. 
 “Arrest of bone maturation in woven bone with ossification
resulting from metaplasia of a nonspecific fibro-osseous
type“
 FD can occur in both types of bones, endochondral and
membranous.
 FD involves maxillary bone,also as the zygoma,
sphenoid, temporal, orbital, nasal, frontal, and occipital
bones.
 Involvement of facial and cranial bones in FD occurs in
nearly 50% of patients with the polyostotic form and in 10-
27% of patients with MFD.
 <1% malignant tranformation.

5. 
 First or second decades of life.
 slow-growing, painless
 expansion of the bone.
 Facial asymmetry may be apparent.
 Visual disturbances, proptosis, orbital dystopia, nasal
malfunction, dental problems and sensory
disturbances in the affected regions.
FD

6. 
 Extraosseous Manifestations:
 McCune-Albright syndrome (MAS):
 polyostotic FD,
 skin hyperpigmentation (café au lait spots),
 multiple endocrinopathies - gonadal hyperfunction
- sexual precocity
(especially in
females).
 hyperthyroidism,
 adenomas of various endocrine glands including the pituitary
gland, Cushing syndrome, acromegaly,
 benign ovarian cysts, linear epidermal nevi, and
 Neonatal cholestasis.
 The skin spots often are unilateral and ipsilateral to the FD
Fibrous dysplasia

7. 
 Mazabraud syndrome:
 polyostotic FD and intramuscular myxomas
FD

8. 
 Osteoma is the most common tumor of the paranasal sinuses.
 male predominance.
 Etiology:3 theories
 Developmental theory:
 apposition of membranous and endochondral tissues traps
some of these embryonic cells, eventually leading to unchecked
osseous proliferation.
 Traumatic theory:
 inflammatory process as the inciting force for bony tumor
formation.
 Infectious theory:
 infectious theory suggests that osteitis resulting from chronic
infection is to blame.

9. 
 surface of an osteoma is
smooth and lobulated
 H/E:3 types
 Eburnated type- ivory or
compact type, is very dense
and lacks haversian canals.
 The mature type- or
osteoma spongiosum, is
composed of softer bone
more similar to cancellous
bone.
 The mixed type of osteoma
contains elements of both
the eburnated and mature
forms

10. 
Fibrous
dysplasia
 Early FD usually exhibits
a moderately cellular,
fibrous stroma containing
haphazardly arranged,
uniform, spindle-shaped
to ovoid fibroblasts.
variable number of small,
ovoid blood vessels are
seen within the stroma,
and collagen bundles
often are scant.

11. 
FD
 Scattered, irregularly shaped
trabeculae of woven bone are
seen throughout the stroma.
 Delicate and curvilinear and
have been likened to Chinese
scrip-writing.
 The lesional bone fuses with
the adjacent uninvolved bone.
 Focally scattered, small, ovoid
calcifications also may be
seen.
 Artifactual separation of the
lesional bone from the
surrounding stroma

12. 
 Cherubism formerly was described as familial fibrous
dysplasia.
 Cherubism is a rare, autosomal dominant, self-
limiting disorder that exhibits 100% male and 50% to
70% female penetrance.
 Clinical manifestations of cherubism are restricted to
the jawbones.
 Mutations in the SH3BP2 gene, found on
chromosome 4p16, have been identified
CHERUBISM

13. 
 identified during early
childhood.
 Patients typically have
painless, bilateral, symmetric
jaw enlargement resulting in
marked facial expansion.
 continues until puberty, after
which the lesions tend to
undergo spontaneous
resolution.
 Diffuse involvement of the
maxilla also may occur.If so,
the midface may become
expanded, resulting in
exposure of the inferior portion
of the sclerae. As a result, the
patient’s eyes may appear to
be looking upward.

14. 
 numerous fibroblasts ,
extravasated RBCs
,and multinucleate giant
cells .

15. 
OSSIFYING FIBROMA
 OFs are considered to be
true benign fibro-osseous
neoplasms that develop
mainly within the
jawbones.
 third and fourth decades
of life.
 small asymptomatic
lesions, slow-growing,
expanding lesions that
often average more than
3 cm in diameter at the
time of diagnosis.

16. 
 balanced translocations with recurring breakpoints at
Xq26 and 2q33.
 OF is a well-circumscribed, occasionally
encapsulated mass that may show a variety of
different microscopic patterns.

17.  moderately cellular, relatively
avascular, dense fibrous stroma.
 cells appear spindle-shaped to
ovoid and may be haphazardly
arranged or organized in a vague
storiform pattern.
 The nuclei are bland appearing
and contain single, inconspicuous
nucleoli.
 calcified material may consist of
thin, irregularly shaped
trabeculae of woven bone;
 scattered trabeculae of lamellar
bone; deposits of basophilic
staining, round or ovoid, cellular
or acellular calcified deposits that
have been likened to cementum.

18. 
 Owing to the presence
of the calcified
spherules,“cemento-
ossifying fibroma” or
“cementifying fibroma.”
 the lesional bone in
OFs does not fuse to
adjacent uninvolved
cortical bone

19. 
 Hyperparathyroidism–jaw tumor syndrome is an
autosomal dominant disease.charactarised as OF.
 Adenoma induced,primry hyperparathyroidism and
well-circumscribed BFOLs of the jawbones.
 renal anomalies-
-renal hamartomas,
-polycystic kidney disease,
-multiple degenerative cysts

20. 
Juvenile ossifying
fibroma
 Trabecular variant (TJOF)
 Psammomatoid variant (PJOF)
 the first and second decades of
life.
 75% of PJOFs develop in the
orbit, paranasal sinuses, and
calvaria,
 Whereas 25% of all cases involve
the maxilla or mandible.
 95% of the documented cases of
TJOF have developed within the
jawbones, with maxillary lesions
occurring more frequently.
 Occasionally of TJOF have arisen
within the fronto-ethmoid complex
and sinonasal bones.

21.  unencapsulated lesion composed
of a cell-rich stroma, usually with
little collagen.
 Reactive bone may be seen at
the periphery of the lesion, but
the lesional tissue often is seen
infiltrating the surrounding normal
bone.
 cells are spindle-shaped to ovoid,
contain bland-appearing nuclei
and inconspicuous nucleoli, and
may be arranged in a storiform
pattern.
 Focally scattered, typical mitotic
figures may be seen.

22. 
 TJOF, delicate “seams” of
osteoid rimmed by
osteoblasts seem to arise
from within the stroma.3
Plump, eosinophilic
osteoblasts often are
incorporated within the
osteoid. Scattered, irregularly
shaped trabeculae of woven
bone and occasional calcified
spherules also are seen.
 PJOF usually are basophilic,
acellular, and round or ovoid
and may resemble
psammoma bodies.

23. 
 The term dysplasia refers to the abnormal production
and disordered development of bone and cementum-
like material.
 3 nonhereditary subtypes
–periapical osseous dysplasia.
- focal osseous dysplasia.
- florid osseous dysplasia.
Osseous dysplasia

24. 
 Periapical Osseous Dysplasia:
 Periapical osseous dysplasia is almost always
asymptomatic and nonexpanding.
 found in intimate association with the root apices of the
mandibular anterior teeth.
 Focal Osseous Dysplasia:
 asymptomatic, manifesting most commonly as a small,
solitary, relatively well-demarcated lesion in the posterior
mandible, either in close association with the apices of
teeth or in areas where a tooth has been extracted
previously.

25. 
 Florid Osseous Dysplasia:
 an innocuous, self-limiting disease.
 involves the posterior regions of the mandible,
manifesting as bilateral, relatively symmetrical
lesions.
 simultaneous, bilateral involvement of both jaws is
very common.
 dull, intermittent, poorly localized pain, especially in
lesions that are infected secondarily.

26. 
 hypercellular, fibrous
connective tissue
containing numerous
small, round or ovoid,
vascular channels.

27. 
 Numerous irregularly
shaped trabeculae of
woven bone embedded
within a fibrous stroma
containing numerous
small blood vessels .

28. 
 Round, cementum-like
calcifications

29. 
 Large aggregate of
acellular bone that has
coalesced in a patient
with florid osseous
dysplasia.

30. 
Familial Gigantiform
Cementoma
 Another autosomal dominant
disorder that is
characterized by florid
osseous dysplasia–like
lesions of the jawbones.
 no sex, age, or racial
predilection for FGC.76,77
Lesions often manifest at an
early age and may cause
substantial rapid bony
expansion and facial
asymmetry.
 polyostotic benign fibro-
osseous disease

31. 
 trabeculae of immature
bone and irregular
basophilic cemental
masses in a moderately
cellular fibrous
connective tissue
stroma

32. 
 Disease Processes That May Be Included in the Differential Diagnosis
of a Benign Fibro-osseous Lesion
 Paget disease of bone
 Low-grade osteosarcoma
 Osteoblastoma
 Osteoid osteoma
 Cementoblastoma
 Central odontogenic fibroma
 Proliferative periostitis
 Renal osteodystrophy
 Central giant cell granuloma
 Brown tumor
 Aneurysmal bone cyst
 Cherubism

33. 
Pagets disease
 PDB may be a monostotic or
a polyostotic disease.
 The maxilla is involved more
commonly than the
mandible.
 Associated nasal obstruction
and sinus obliteration also
are typically seen.
 A fibro-osseous pattern
typically is seen. However,
prominent basophilic
reversal lines usually are
observed within many of the
bony trabeculae

34. 
Central Giant Cell
Granuloma
 CGCGs may develop within
the maxilla, most cases
manifest within the mandible.
 hypervascular, hypercellular,
collagenous stroma exhibiting
a variable number of
osteoclast-like multinucleated
giant cells.
 stromal cells are bland
appearing and spindle-
shaped to
 ovoid and often are arranged
in a haphazard manner

35. 
 Bone lesions develop in an estimated 10% to 15% of
patients with hyperparathyroidism
Brown Tumor
(Hyperparathyroidism)

36. 
Aneurysmal Bone Cyst
 About 10% of ABCs develop in
the maxillofacial bones.
 association with FD, OF, JOF,
osteoblastoma, and
osteosarcoma.
 overlap between ABCs
 and CGCGs.3,129,134 The
only significant difference is
that
 ABCs exhibit numerous large,
blood-filled, sinusoidal spaces
that are surrounded by
multinucleated giant cells.
 Extravasated hemorrhage and
hemosiderin deposits also are
seen.

37. 
Thank you