Pathology of fibro osseous lesions

pathology

1. PATHOLOGY OF FIBRO OSSEOUS LESIONS Dr.Roohia

2. 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

3. “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. I nvolvement 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 .

4. F irst or second decades of life. slow-growing, painless expansion of the bone. Facial asymmetry may be apparent. V isual disturbances, proptosis , orbital dystopia, nasal malfunction, dental problems and sensory disturbances in the affected regions.  FD

5. 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 lesions . Fibrous dysplasia

6. Mazabraud syndrome: polyostotic FD and intramuscular myxomas FD

7. 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.

8. surface of an osteoma is smooth and lobulated H/E:3 types E burnated 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

9. 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.

10. FD Scattered, irregularly shaped trabeculae of woven bone are seen throughout the stroma . D elicate and curvilinear and have been likened to Chinese scrip-writing. T he 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

11. 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

12. 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. D iffuse 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.

13. numerous fibroblasts , extravasated RBCs , and multinucleate giant cells .

14. 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 .

15. 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.

16. 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 .

17. 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

18. 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

19. Juvenile ossifying fibroma T rabecular 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.

20. 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.

21. 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.

22. 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

23. 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.

24. 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.

25. hypercellular , fibrous connective tissue containing numerous small, round or ovoid, vascular channels .

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

27. Round, cementum -like calcifications

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

29. 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

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

31. 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

32. 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

33. 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

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

35. 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.

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