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In addition to the peripheral giant cell granuloma, mesenchymal cells of the periodontal ligament are capable of producing another unique inflammatory hyperplasia, the peripheral ossifying fibroma, also referred to as the peripheral cementifying fibroma, depending on whether or not bone or cementum is seen microscopically. The pluripotential cells of the ligament have the apparent ability to transform or metaplastically alter into osteoblasts, cementoblasts or fibroblasts. The reader is reminded that this is a reactive lesion, not the peripheral counterpart of the intraosseous neoplasm called central cemento-ossifying fibroma. Odontogenic lesions of the gingiva, moreover, may produce various calcified materials and are discussed elsewhere in this book.
By definition, the peripheral ossifying fibroma must be associated with gingival
tissues, and the diagnosis cannot be used for lesions of other oral sites.
The presence of teeth is not, however, required for the diagnosis, as periodontal
ligament fibers remain within and above alveolar bone long after their associated
teeth have been extracted. Shepherd first reported this entity
as alveolar exostosis in 1844.
Peripheral ossifying fibroma presents as a painless, hemorrhagic and often lobulated mass of the gingiva or alveolar mucosa (Figures 1 & 2), perhaps with large areas of surface ulceration. Early lesions are quite irregular and red, but older lesions may have a smooth salmon pink surface and may be indistinguishable clinically from the more common irritation fibroma. Most lesions are 1-2 cm. in size, but some may slowly enlarge to more than 4 cm. Early growth is often alarmingly rapid.
A lesion may vary somewhat in size over time, depending on the amount of
superficial inflammation and edema. While this tumor is typically diagnosed
in teenagers and young adults, it may occur at any age, especially in individuals
with poor oral hygiene. Radiographs may show irregular, scattered radiopacities
in the lesion (Figure 3).
Pathology and Differential Diagnosis
An aggregated submucosal proliferation of primitive oval and bipolar mesenchymal cells is the hallmark of peripheral ossifying fibroma. The lesion may be very cellular or may be somewhat fibrotic, but scattered throughout are islands and trabeculae of woven or lamellar bone, usually with abundant osteoblastic rimming (Figures 4 & 5). Metaplastic bone may also be seen. The calcified tissues may have the dark-staining, acellular, rounded appearance of cementum, in which case the term peripheral cementifying fibroma has traditionally been used (Figure 6). Many examples show an admixture of bone and cementum, i.e. peripheral ossifying/cementifying fibroma, and early lesions may contain only small ovoid areas of dystrophic calcification. While the lesional stroma is similar to that of peripheral giant cell granuloma, the erythrocyte extravasation of the latter lesion is not a feature of peripheral ossifying fibroma and osteoclast-like cells are quite rare.
The lesional nidus is not encapsulated but is rather well demarcated from
the surrounding fibrovascular stroma. Surrounding tissues are often edematous,
with neovascularity and variable numbers of chronic and acute inflammatory
cells. By way of differential diagnosis the exuberant callus
common to the long bones is almost never found at the surface of jawbones,
hence, is not a serious diagnostic distinction from peripheral ossifying
fibroma. Some gingival masses, however, contain large areas of classic
pyogenic granuloma, irritation fibroma or peripheral giant
cell granuloma, as well as peripheral ossifying fibroma. In such cases the
pathologist usually chooses for the appropriate diagnosis the lesional type
that predominates. Also, individual cells must be carefully examined for
dysplastic changes in order to rule out osteoblastic
osteosarcoma or juxtacortical
osteosarcoma, but frequent mitotic figures of normal configuration are
acceptable for the benign diagnosis, especially in lesions found in children.
Treatment and Prognosis
Conservative surgical excision must be followed by diligent curettage of the wound and root planing of adjacent teeth if recurrence is to be avoided. With simple removal the recurrence rate is greater than 20%. Malignant transformation has not been reported for this lesion.
References (Chronologic Order)
Note: General references can be found by clicking on that topic to the left.
Shepherd SM. Alveolar exostosis. Am J Dent Sc 1844; 4:43-44.
Buchner A, Hansen LS. The histomorphologic spectrum of peripheral ossifying fibroma. Oral Surg Oral Med Oral Pathol 1987; 63:452-461.
Kenney JN, Kaugers GE, Abbey LM. Comparison between the peripheral ossifying fibroma and peripheral odontogenic fibroma. J Oral Maxillofac Surg 1989; 47:378-382.
Zain RB, Fei YJ. Fibrous lesions of the gingiva: a histopathologic analysis of 204 cases. Oral Surg Oral Med Oral Pathol 1990; 70:466-470.
Poon CK, Kwan PC, Chao SY. Giant peripheral
ossifying fibroma of the maxilla - report of a case. J Oral Maxillofac Surg 1995; 53:695-698.
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