Bone and Soft-Tissue Disorders
= encapsulated circumscribed benign neoplasm closely related to fibrous dysplasia + adamantinoma
Incidence: peaks in 3rd–4th decade
Age: 2nd–4th decade; M <F
Histo: highly cellular fibrous connective tissue composed of spindle cells with osteoblastic activity producing varying amounts of osteoid in a pattern of uniform small round lamellated “psammoma-like” ossicles; irregular spicules / trabeculae of lamellar bone rimmed by osteoblasts (DDx from fibrous dysplasia)
Subtypes:
- cementifying fibroma
- cemento-ossifying fibroma
- juvenile ossifying fibroma: aggressive destructive, most common in boys <15 years of age
Location: frequently in face / posterior mandible
- asymptomatic
- tooth displacement; facial asymmetry ← bone expansion
- intense focal uptake on bone scan
- Tibia
- eccentric ground-glass lesion (resembling fibrous dysplasia)
- initially lucent (= nonmineralized osteoid) + later often opaque lesion (depending on degree of calcification) similar to fibrous dysplasia
- surrounded by thin line of lucency (= fibrous capsule) + thin outer rim of sclerotic (reactive) bone
- ± soft-tissue enhancement
- Mandible, maxilla
Site: premolar / molar region
- painless swelling of tooth-bearing portion of jaw
- 1–5 cm well-circumscribed round / oval tumor
- moderate unilocular expansion of intact cortex
- homogeneous tumor matrix
- dislodgment of teeth
- NO halo of low attenuation; sclerotic border (occasionally)
Cx: significant potential for centrifugal growth perpendicular to long axis of bone; frequent recurrences
DDx:
- Fibrous dysplasia (longitudinal growth pattern, nondisplaced teeth, crossing of sutures, osteoblastic rimming, NO radiolucent boundary)
- Odontoma
- Sequestrum
- Vascular lesion
Juvenile Ossifying Fibroma
= PSAMMOMATOID OSSIFYING FIBROMA
= nonmetastasizing benign tumor that arises in sinonasal region of young patients often involving orbit with tendency for locally aggressive behavior
Age: children and adolescents; M÷F = 1÷1
Location: facial bones (85%), esp. paranasal sinuses; more than one sinus in ½
Site: ethmoid region / superior orbital plate of frontal bone
- proptosis, headache, sinusitis
- facial swelling, nasal obstruction
- visual / ocular motility disturbance
- intracranial extension
Radiography:
- monostotic round / ovoid well-demarcated expansile lesion of mixed lytic + sclerotic density
- ballooned / bowed appearance of sclerotic margin
CT:
- predominantly soft-tissue attenuation with multiple foci of calcifications
- ± multiloculated internal composition with sclerotic septa / enhancing septa of soft-tissue attenuation
- lower-attenuation areas ← cystic changes
- usually surrounded by a possibly partially disrupted sclerotic rim / shell
- enhancement of shell + solid tumor portions
MR:
- lesion isointense relative to muscle on T1WI
- hypointense relative to muscle on T2WI
- foci of high T2-signal intensity ← fluid-filled cystic spaces
DDx: fibrous dysplasia, cementifying fibroma (arises from periodontal ligament in molar teeth), aneurysmal bone cyst (infrequently in sinonasal region, fluid levels throughout its cystic component)