Oral & Maxillofacial Pathology - Bone Lesions - PDF

# Oral&Maxillofacial Pathology ## Bone Lesions ### Fibro-osseous Lesions A group of lesions characterized microscopically by fibrous stroma containing various combinations of bones and/or cementum-like material fall under the term benign fibro-osseous lesions. They include a wide variety of lesions...

# Oral&Maxillofacial Pathology ## Bone Lesions ### Fibro-osseous Lesions A group of lesions characterized microscopically by fibrous stroma containing various combinations of bones and/or cementum-like material fall under the term benign fibro-osseous lesions. They include a wide variety of lesions of developmental, dysplastic, and neoplastic origins with different clinical and radiographic presentation & behavior. Because of the histologic similarities between these diverse diseases, proper diagnosis requires clinical findings, radiographic features, surgical notes and histopathologic correlation to establish a specific diagnosis. Among the fibro-osseous lesions of the jaw are the following: 1. Fibrous dysplasia. 2. Cemento-osseous dysplasia. 3. Ossifying fibroma. ### Fibrous Dysplasia (FD) FD is a skeletal anomaly in which normal bone is replaced and distorted by poorly organized & inadequately mineralized, immature, woven bone & fibrous connective tissue. The disease may affect a single bone *(monostotic)* or multiple bones *(polyostotic)*. #### Etiology & Pathogenesis: The nature of this condition has not been firmly established. FD is a sporadic condition that results from a postzygotic mutation in the *GNAS1* *(guanine nucleotide binding protein, a-stimulating activity polypeptide 1)* gene. Clinically FD may manifest as a localized process, as a condition involving multiple bones, or as multiple bone lesions in conjunction with cutaneous & endocrine abnormalities depending on the time that the mutation of *GNAS1* occurs. 1. Mutation occurs in early embryonic life - mutation in one of undifferentiated stem cells, presented as multiple bone lesions, cutaneous pigmentation & endocrine disturbances. 2. Mutation occurring during later stages of embryonic development of the skeletal system - multiple bone involvements. 3. Mutation during postnatal life - mutated cells confines to one site FD of a single bone. ### Clinical Features of FD: The condition presents commonly an asymptomatic, slow enlargement of the involved bone. - **Monostotic FD** is the term used to describe the process in one bone. - **Polyostotic FD** applies to cases in which more than one bone is involved. Its types are:- - **McCune-Albright syndrome** consists of polyostotic FD, cutaneous melanotic pigmentations *(café-au-lait macules)* and endocrine abnormalities. - **Jaffe-Lichtenstein syndrome** is characterized by multiple bone lesions of FD & skin pigmentations. - **Monostotic FD** much more common than the polyostotic form, accounting 80% of cases. Jaw involvement is common in this form of disease. Other bones that are commonly affected are the ribs & femur. 1. Occurs more often in the maxilla than in the mandible. 2. Maxillary lesions may extend to involve the maxillary sinus, zygoma, sphenoid bone and the floor of the orbit. This form of the disease, with the involvement of several adjacent bones, has been referred to as **craniofacial FD**. 3. Jaw involvement is usually slow & painless, typically a unilateral swelling. 4. Teeth displacement may occur, with malocclusion and interference with tooth eruption, without tooth mobility. 5. The condition characteristically has its onset during the 1st & 2nd decade of life. 6. FD usually exhibits an equal sex distribution & the polyostotic form tends to occur more commonly in females. ### Radiographic Findings: FD has a variable radiographic appearance that ranges from a radiolucent lesion to a uniformly radiopaque mass. Classical presentation is **ground-glass effect**, which results from the superimposition of poorly calcified bone trabeculae arranged in a disorganized pattern. Radiographically, the lesions of FD are not well demarcated. An important feature of FD is the poorly defined radiographic and clinical margins of the lesion that blend into the surrounding normal bone. ### Lab Findings: Serum calcium, Phosphorus & Alkaline phosphatase are normal in monostotic FD, but altered in McCune-Albright syndrome. ### Histopathology: FD consists of a slight to moderate cellular fibrous connective tissue stroma that contains foci of irregularly shaped trabeculae of immature bone. The bone trabeculae assume irregular shapes linked to *Chinese letters*, and they do not display any functional orientation, without osteoblastic activity at the bone trabeculae margins. ### Treatment & Prognosis: After a variable period of prepubertal growth, FD stabilizes, although a slow advance may be noted into adulthood. - Small lesions - No treatment - Large lesions - Cosmetic or functional deformity-----surgical recontouring. ### Cemento-osseous Dysplasia (COD): The term COD refers to a disease process of the jaws for which the precise etiology is unknown. COD includes: - Periapical COD: - Focal COD: - Florid COD: All the 3 disease processes have the same features, only distinguished on the basis of the extent of involvement of the affected portions of the jaw. 1. **Periapical COD:** A common phenomenon that occurs at the apex of vital teeth. Represents a reactive or dysplastic process rather than a neoplastic one. It may represent an unusual response of periapical bone & cementum to some undetermined local factor. 2. **Focal COD:** When not associated with a tooth apex. ### Clinical Features: A biopsy is unnecessary because the condition is usually diagnosed by clinical & radiographic features. Females are affected more than males. *(around 40 years)*. The mandible, especially the anterior periapical region, is far more commonly affected than other areas. More often, the apices of two or more teeth are affected. #### Radiographic features - The condition appears 1st as a periapical lucency that is continuous with the periodontal ligament space. To be differentiated from **Periapical granuloma – vitality test**. - As the condition progresses, the lucent lesion develops into a mixed or mottled pattern because of bone repair. - The final stage appears as a solid, opaque mass that is surrounded by a thin, lucent ring. 3. **Florid COD:** The FCOD is an exuberant form of PACOD. FCOD represents the severe end of the spectrum of this unusual process. The patient is asymptomatic except when complication of osteomyelitis occurs. Females are more commonly affected *(black women)*; between 25-60 years of age. The condition is typically bilateral & may affect all four quadrants. Radiographically, FCOD appears as diffuse radiopaque masses throughout the alveolar segment of the jaw. A *ground-glass* or cyst-like appearance may also be seen. ### Diagnosis: | Clinical | Radiographical | Histopathology to confirm if necessary | |---|---|---| | Black female&nbsp; | PA - single&nbsp;<br> Florid&nbsp;<br>Multiple&nbsp; | + Vital teeth | - Lucent Stage: Less bone trabeculae - Mature radiopaque: Solid sclerotic masses of bone or cementum ### Histopathology of COD: All 3 types show a mixture of benign fibrous tissue, bone, and cementum. The calcified tissue is arranged in trabeculae, spicules or larger irregular masses. Numerous small blood vessels & free hemorrhage is typically noted throughout the lesion. The proportion of the mesenchymal component to the mineralized material is *variable* depending on the stage and from area to area in the same lesion. ### Treatment: No treatment. ### Ossifying Fibroma OF is a benign neoplasm of bone that has the potential for excessive growth, bone destruction & recurrence. Clinically & microscopically similar to cementifying fibroma, it is composed of a fibrous connective tissue stroma in which new bone is formed. OF is a true neoplasm with a significant growth potential. Recently, mutations in a tumor suppressor gene were identified. ### Clinical Features: The epidemiology of Ossifying fibroma is unclear because many previous diagnosed cases were confused with focal cemento-osseous dysplasia (COD). For that reason what was thought to be OF, a common neoplasm, is now considered to be uncommon because most of the cases were in reality focal COD tends to occur during the 3rd & 4th decades of life, in females more than in males. It is a slow growing asymptomatic & expansile lesion. OF may be seen in the jaw & craniofacial bones. Lesions in the jaw arise in the tooth-bearing region, mostly in the molar & premolar area. The tumor may cause expansion of the buccal and lingual cortical plates, however perforation is very rare. OF is mostly a solitary lesion, although multiple lesions have been reported. ### Radiographic Findings of COF: Well circumscribed, sharply demarcated border is the most common presenting radiographic feature, although OF may present as relatively lucent or opaque depending on the density of the calcification present. Also they may be unilocular or multilocular, mixed radiolucent-radiopaque image may be seen. The roots of the teeth present may be displaced & less commonly resorption is seen. ### Histopathology: Cementifying fibroma, cemento-ossifying fibroma (COF), ossifying fibroma are terms used to describe the same condition, since the origin is the stem cells in the periodontal ligament which may give rise to both cementoblasts & osteoblasts forming both cementum & bone which cannot be differentiated on H&E stain. The last term (COF) is the one used by WHO classification. COF is composed of fibrous connective tissue with well- differentiated spindle fibroblasts. Cellularity is uniform but may vary from one lesion to the next. Bone trabeculae or islands are evenly distributed throughout the fibrous stroma. The bone is immature & often surrounded by osteoblast *(osteoblast rimming)*. Osteoblasts are infrequently seen. ### Treatment & Prognosis: Surgical removal using curettage or enucleation. The lesion can typically be separated easily from the surrounding bone. Recurrence is rare. ### Juvenile Ossifying Fibroma: Is a well circumscribed rapidly growing neoplasm lack the continuity with adjacent normal bone. Two different neoplasm have been reported: 1. Trabecular and 2. Psammomatoid. The latter neoplasm occur more than the trabecular type in a ratio of approximately 4:1.