Clinical radiological and histological correlation in the diagnostic work-up of cemento-ossifying fibroma of the maxilla: apropos a case

Introduction
Benign fibroosseous lesions of the jaws present problems in diagnosis and classification. The 1992 WHO classification groups under a single designation (cementoossifying fibromas) two histologic types (cementifying fibroma and ossifying fibroma) that may be clinically and radiographically indistinguishable (1, 2). Cementoossifying fibroma is an uncommon lesion of possible osteogenic (non-odontogenic) origin with variable expressiveness. It is defined as a well demarcated and occasionally encapsulated lesion consisting of fibrous tissue containing variable amounts of mineralized material resembling bone (ossifying fibroma), cementum (cementifying fibroma) or both (3, 4). It is believed to derive from the cells of the periodontal ligament (5-7). This is a layer of fibrous connective tissue surrounding the roots. It contains multi-potential cells capable of forming cementum, lamellar bone and fibrous tissue. Under pathological conditions neoplasms containing any or all of the components may be produced (8). More aggressive lesions usually involve the maxillary antrum where extensive growth is unimpeded by anatonic obstacles. Because all cementum containing lesions are theoretically of periodontal membrane origin, maxillary sinus spread after origin from an upper premolar or molar tooth is a distinct possibility (8). They usually follow a silent clinical course, except of those affecting the gingivae which present as an enlarging mass that grow progressively finally producing a facial deformity. Diagnosis requires careful clinical, radiological and histological correlation (2).

Case report
A 36-year-old woman was referred for evaluation of a mass in the right cheek (fig. 1). The patient stated that the mass had first appeared 4 years ago and was slightly becoming larger ever since. The host had no complaint of pain, visual field disturbances, dysphagia or dyspnea. Her past medical history was uninteresting. The physical examination revealed a maxillary enlargement and an intraoral lesion, which had almost effaced the jugogingival groove. The teeth were agile and displaced. Oral mucosa was normal. Imaging studies demonstrated a mixed density mass in the superior right maxilla with expansile remodeling of bone and focal loss of cortical bone. The mass invaded the maxillary sinus. It was well defined and showed radiolucent and radio-opaque features (fig. 2). CT scan also showed a mixed density mass with diffuse scattered calcification involving the maxillary alveolar ridge, occupying and expanding the right maxillary sinus. A tissue sample was obtained for histopathological study and showed a fibrous connective tissue with bone trabeculae (fig. 3). The most distinctive component was the presence of mineralized or calcified psammomatoid bodies or ossicles. The ossicles were small with an oval shape without associated osteoblastic rimming. The fibrous stroma was characterized by a spindle cell proliferation that showed a storiform pattern. The lining was a non-keratinized stratified squamous epithelium with overlying ulceration and the superficial parts of the lesion consisted of granulation tissue. The lesion was quite hypocellular with no cytological atypia and absence of mitotic activity. A diagnosis of COF was rendered, and the patient underwent surgical resection via a Weber-Fergusson approach (fig. 4).

Discussion
Fibroosseous lesions of the jaws continue to present problems in diagnosis and classification to clinicians and pathologists, despite the advances in our understanding of this entity (3, 9). Wladrom and Giasanti established the basis on benign fibroosseous lesions in 1973. They made three main categories: fibrous dysplasia, reactive lesions (periapical cementoosseous dysplasia, focal cementoosseous dysplasia and florid cementoosseous dysplasia) and fibroosseous neoplasms (3). COF is actually considered as a fibroosseous dysplasia, included in the group of non odontogenic tumors since the 1992 WHO classification (3, 4). It includes different pathologic entities arising from blastic mesenchymal cells from the periodontal ligament. These cells have potential capability to form bone, cementum and fibrous tissue in combination (2,4). Most of these tumors occur in the third and forth decades of life, with a predilection for women (2-4, 9-11). They are commonly located in dentolous maxillary areas (10), with a higher incidence on premolar-molar mandibular area (70%-80%)(2-4, 9-11), although they might appear in ascending ramus of the mandible (3). It has a slow clinical progression which conferes a benign nature. This lesion appears within the bone although in some occasions it involves the gingivae soft tissues (2, 4). Bony tumors have the highest incedence in mandible, followed by the maxilla, zygoma and even the ethmoid bone and premastoid region (2, 3). The clinical evolution of the tumor usually is as follows: Initially asymptomatic, the tumor progressively grows up to a point in which its size causes pain, as well as functional alterations and cosmetic deformities (2, 4). Histologically it is typical to encounter a fibroblastic connective tissue stroma with varying cellularity, although mitoses are rare. Within the fibrous stroma are mineralized tissue masses of basophil aspect that correspond to osteoid or cementoid material. This is distributed throughout the tumor in a greater or lesser quantity and is accompanied by dystrophic calcifications that adopt a basophilic or darker color (12). According to Voytec et al (13) the differences between fibrous dysplasia and COF are not always exhibited in each and every section of the tumor, the reason for which some cases are poorly diagnosed. The histologic pattern of the two lesions coincide in what the authors expressed (12, 14, 15) with respect to a predominantly fibrous cellularity and the presence of masses of cementifying tissues, with greater or lesser grade of calcification. Other differentials include osteoid osteoma, osteoblastoma, chronic osteomyelitis and sclerosing osteomyelitis of Garre (2-4, 9-11) Clinical and radiologic information becomes imperative. Radiographically COF may follow different patterns based on the amount of mineralized tissue. It presents as a well demarcated unilocular lesion, that might have different degrees of opacification inside. It can cause root resorption and teeth displacement (2-4, 9-11). Treatment is surgical and prognosis is excellent. Recurrence is rare if it is correctly managed (2,4). We have not found any case of malignant transformation in the literature.
There is a type of COF called juvenile active, that is seen in children and young people ranged between 5 and 15 years old. It involves the upper maxilla, having a rapid evolution and a tendency to erose surrounding bone. Histologically it consists of cellulo-vascular stroma with varying degrees of giant cells and poor collagen production. Treatment is enucleation and curettage. This type of COF has a higher recurrence rate because of its poorer demarcation, and its higher rate of bone infiltration (3, 4, 11).

References
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