Fibro-Osseous Lesions Flashcards
What is a Fibro-osseous lesion
A lesion in which bone is replaced by cellular fibrous tissue, which grows and then gradually matures back to bone. The degree o maturation varies between diseases and takes many months or years. Sometimes the maturation never proceeds beyond woven bone, or the woven bone may mature further to disorganised lamellar bone or very dense sclerotic amorphous mineralisation
Why is the concept of Fibro-osseous lesions difficult
Because:
- Are defined by their histology - all appear the same
- All share some radiological features - radiolucency, diffuse or patchy sclerosis
- Diagnosis is based on clinical and Radiographic Findings - avoid biopsy
What is fibrous dysplasia and what are the types
- Benign, self-limited replacement of the normal bone by cellular fibrous tissue containing islands or trabeculae of metaplastic bone with no defined margin
- May affect one bone (monostotic), or many (polyostotic) or many in Albright’s syndrome
What is the aetiology of monostotic fibrous dysplasia
- GNAS1 mutation that occurs late in development, so the clone of affected cells is present only in one bone
- In the affected region, the activated fibroblasts and osteoblasts grow excessively , but they remain under some degree of growth control
- Progressive growth and expansion usually develop at a time when the bone would normally be growing and ceases around the time the bone would l normally be mature (skeletal maturation)
What are the clinical features and how is monostotic fibrous dysplasia diagnosed
Features
- Enlargement of one bone, one jaw - usually maxilla (zygomatic process)
- Localised swelling
- Often painless and smoothly rounded
- Initially the teeth are aligned, but if the mass becomes large it will displace teeth
- May have missing teeth and enamel Hypoplasia, but the dental defects are mild
Two key diagnostic features:
- Lesions merge imperceptibly with normal bone at margins
- Always expansion of bone
What are the radiographic features of monostotic fibrous dysplasia
- Radiolucent
- Ground glass or orange peel pattern
- No clear margin
- Loss of normal bone pattern: trabeculae, cortex and lamina dura
- The degree of radiopacity increases, and late lesions are sclerotic and lack the trabecular pattern of normal bone
What are the histological features of monostotic fibrous dysplasia
- Normal bone replaced by fibrous connective tissue containing slender trabeculae of woven bone in C, S and Y shapes
- Gradual maturation to lamellar bone
What is the treatment of monostotic fibrous dysplasia
- The disease is self-limiting, but lesions become quiescent rather than resolve
- The lesion is not well demarcated and cannot be excised
- Treatment must be delayed until growth of the bone has ceased
What are the complications of monostotic fibrous dysplasia
- Development of sarcoma 1% (usually osteosarcoma)
- Higher risk if treated by radiotherapy, GNAS mutation increase growth
What are the features of polyostotic fibrous dysplasia
- Involves head and neck in as many as 50% of cases
- A jaw lesion may then be the most conspicuous feature and polyostotic disease should be screened of involvement of other bones and for the features of Albright’s syndrome
- Long bone involvement causes most problems, with bowing of weight bearing bones, bone pain and pathological features
- Histologically and radiographically, the individual lesions are indistinguishable from the monostotic form
What are the features of Albright’s syndrome
- Comprises polyostotic fibrous dysplasia, skin pigmentation and endocrine abnormalities
- Most pts are girls aged less than 10 at onset
- Bone lesions are more numerous than in non-syndromic polyostotic fibrous dysplasia
- More than 75% of cases have one or both jaws involved
- Nearly all have skull involvement
- Skin pigmentation: brown macula’s with irregular outlines
- Histologically and radiographically the lesions are indistinguishable from monostotic form
What are cemento-osseous dysplasias and what are the three presentations
- Non-neoplastic disturbances of growth and remodelling of alveolar bone and cementum
- 3 presentations: periapical, focal, florid
- All have similar histological and radiological features
- Differ mainly in their extent and radiographic appearances
- Asymptomatic, often chance radiographic finding
- Strong predilection for females and africans 30-50y
- Most common Fibro-osseous disease of jaw
Clinical features of periapical cemento-osseous dysplasia
- In the periapical form, several adjacent teeth are affected, usually lower incisors
- Often chance finding of rounded radiolucent areas related to apices of the teeth. These stimulate periapical granulomas
- Over a few years, the separate lesions enlarge and may fuse and develop internal calcification. Mineralisation starts centrally and gives each lesion a target-like appearance radiographically
- Eventually lesions cease to enlarge, rarely exceeding 8-10mm and become densely radiopaque
- All stages of development may be seen at the same time in different lesions in the same pt
- Teeth remain vital throughout
Clinical features of focal cemento-osseous dysplasia
- This term is given to changes similar to florid osseous dysplasia but forming a single lesion on one tooth
- Lesion resembles a cemento-osseous fibroma radiographically but shows the maturation sequence typical of this group of lesions
- Lesions are usually in the posterior mandible
Clinical features of florid cemento-osseous dysplasia
- Multiple teeth are affected in more than one quadrant
- Affected areas are frequently symmetrically distributed and may involve all teeth in all four quadrants, although the mandibular teeth are more commonly and more severly affected in most cases
- Individual lesions develop around the root apices exactly as in periapical form but become larger and occasionally expand the jaw
- The target-like appearance with central sclerosis resembling cementum on the root apex, surrounded by radiolucent trim with further outer zone of sclerosis in the surrounding bone is characteristic
- Eventually dense radiopaque irregular masses of sclerotic bone without radiolucent border develop, producing radiographic appearance similar to chronic osteomyelitis
- Tooth vitality unaffected
- Solitary bone cysts can develop in association with lesions
