Rapidly Growing Expansile Lesion of the Left Jaw in a 15-Year-Old Boy.
The periodontal examination revealed a profound buccai expansion of the left posterior mandible extending from the distal side of the second primary molar to involve the ramus. The lesion clinically felt firm and appeared unilocular with no detectable bruit or thrill. The panoramic radiograph depicted a radiolucent, poorly circumscribed expansile mass extending from the distal left mandibular first premolar and beyond the unerupted mandibular third molar into the ramus, angle, and coronoid process, measuring 4.0 x 3.0 x 2.5 cm (Figure 1). The patient underwent a diagnostic biopsy and subsequently a therapeutic enucleation and aggressive curettage. Surgical specimens from both the original biopsy and succeeding therapeutic procedure were processed for light microscopic examination.
Hematoxylin-eosin-stained sections revealed a predominance of spicules of irregular woven bone and nonuniformly distributed trabeculae of lamellar bone, both of which were embedded within a highly cellular, spindle-shaped, fibroblastic stroma in a storiform arrangement. In addition, variable numbers of scattered osteoclast-like giant cells and brisk osteoblastic rimming of the trabecular bone were noted. Cytologic atypia was absent and mitotic figures were not seen (Figure 2).
What is your diagnosis?
Pathologic Diagnosis: Juvenile Aggressive (Active) Ossifying Fibroma Presenting as a Posterior Mandibular Mass
Since the first description of this entity as osteoid fibroma with an atypical calcification by Benjamins in 1938, juvenile active ossifying fibroma has confounded clinicians and pathologists for decades. It was not until 1952 that Johnson et al coined the term juvenile active (aggressive) ossifying fibroma (JAOF). The term was further established by a comprehensive review of 112 cases selected from 3000 fibro-osseous lesions collected at the Armed Forces Institute of Pathology during a period of more than 45 years. Regrettably, many synonymous nomenclatures of this single entity exist, such as least differentiated form of fibro-osteoma, ossifying fibroma (OF), young OF, cementifying fibroma, and psammomatoid OF. These variations have been a source of much confusion and debate in the literature and underscore the propensity for this lesion to be misdiagnosed. In general, fibro-osseous lesions of the craniofacial skeleton are rare and present a diagnostic dilemma for clinician and pathologist alike, owing to overlapping clinical and histomorphologic findings.
Establishing a histologic distinction among these entities is difficult, as is reproducing the results, even with rigorous application of strict criteria. It has been proposed that the mesenchymal cells of the periodontal membrane (connective tissue that anchors the tooth to the alveolar ridge) serve as multipotential precursor cells capable of differentiation into cementum, osteoid, or fibrous tissue and give rise to a spectrum of fibro-osseous lesions. In general, JAOF commonly occurs in patients between the ages of 5 and 15 years and is more often seen in males than females.
In 84% of the patients with JAOF, the tumors are located in the facial bones, but calvaria (12%) and extracranial sites (4%) can be involved. Among the facial tumors, 90% arise from the paranasal sinuses and the remaining 10% involve the mandible. It is believed that lesions involving such extragnathic sites may not represent the same pathologic process, because the histopathologic features are different and their behavior is more aggressive.
The mandibular lesions typically occur in a posterior region and frequently are found in the angle of the mandible. According to some investigators, they perhaps originate from maldevelopment of the tissue generating the bony septa between the roots of molar teeth. There are no well-defined morphologic criteria to distinguish this tumor from the more common forms of OF; however, the juvenile tumors behave differently by their painless and rapidly expanding growth and so are referred to as "active" or "aggressive" OF.
Imaging studies including a plain film are essential in the evaluation of patients and provide helpful clues toward the diagnosis. However, in general, there are no reliable radiologic differences among the various fibro-osseous lesions. Radiographically, OFs are classically described as circumscribed unilocular lesions that are often surrounded by an eggshell-thin rim of bone. Aggressive forms of OF tend to show more of an expansile growth pattern than the typical variety; however, they still tend to exhibit sharp demarcation from the normal adjacent bone. The clinical differential diagnosis in conjunction with radiographic findings in this patient initially included non-odontogenic primary tumors of bone, such as osteoblastoma, aneurysmal bone cyst, central giant cell granuloma, osteogenic sarcoma, progressive monostotic fibrous dysplasia (FD), and juvenile OF. In addition, less likely consideration included locally aggressive odontogenic lesions, such as ameloblastic fibro-odontoma, as well as other entities consisting of calcifying odontogenic cyst (Gorlin cyst), adenomatoid odontogenic tumor, and primordial cysts (keratocyst). Vascular tumors also can have rapid growth and should be considered in the differential diagnosis. For example, central hemangiomas grow rapidly and commonly present as a radiolucent mandibular mass in children and young adults. Arteriovenous malformations also exhibit rapid growth, but usually display thrills or bruits on examination.
On gross inspection, JAOF appears as a yellow-white, homogeneous, and firm lobulated mass with a gritty consistency. Cystic spaces, although rare, can be present. Histologically, aggressive and nonaggressive forms of OF show analogous morphologic features. Perhaps the most significant diagnostic pitfall is an accurate distinction from FD. As described by Fechner classic FD and OF represent opposite ends of the microscopic spectrum of benign proliferative fibro-osseous lesions. A histologic hallmark of OF includes irregularly distributed woven and interconnecting lamellar bone with prominent osteoblastic rimming within a hypercellular spindle cell, fibroblast-like stroma admixed with variable numbers of randomly distributed osteoclast-like giant cells. The cytologic atypia is minimal, and mitotic figures are rarely seen. This is in contrast to the closely related FD, which at times is indistinguishable morphologically from JAOF. However, the following parameters have been suggested to separate these entities: the lack of circumscription, a generally uniform bone-to-fibrous tissue ratio, with evenly scattered bony trabeculae amidst the fibrous background, and lack of consistent osteoblastic rimming of the trabecular bone are said to favor FD. The differentiation between these 2 entities is of great importance and merits careful consideration because of their divergent clinical behavior. Fibrous dysplasia is usually a self-limiting disease, and therefore a complete resection is unnecessary and in most instances is impossible. In contrast, JAOF is a genuine neoplasm, which should be completely removed.
Treatment of JAOF has been controversial. Complete removal by enucleation alone or with curettage as well as en block resections are common therapeutic options. As much of the mass as possible must be removed while protecting adjacent vital structures to prevent recurrences. The current case required curetting of adjacent normal-appearing surrounding tissue to ensure total excision of the mass. The reported recurrence rate ranges between 30% and 58%. Radiotherapy has been proven ineffective and is contraindicated due to an increased incidence of malignant transformation, ranging from 0.4% to 40%. Despite the aggressive behavior, no metastasis has been reported. Therefore, conservative treatment of the jaw lesions by enucleation and curettage has been reported to be successful. Our patient had an uneventful postoperative course, and after 10 months of close clinical and radiographic follow-up, there was no evidence of residual or recurrent disease.
In summary, JAOF is a rapidly growing benign but aggressive neoplasm that is encountered most commonly in children and young adults. Histologic criteria for accurate classification remain complicated and are often controversial, secondary to confusing terminology as well as overlapping morphologic features shared by several closely related entities. Consequently, accurate and reliable diagnosis of JAOF requires a multidisciplinary approach with close attention to pertinent clinical history, radiographic impression, and correlation with histomorphologic findings. The management of these lesions is directed at primarily surgical intervention and must consist of a complete resection, since partial removal is associated with the hazard of recurrence.
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Accepted for publication December 14, 2000.
From the Departments of Pathology and Laboratory Medicine (Drs Javadzadeh and Park) and Surgery (Dr Means), East Carolina University, Brody School of Medicine, Greenville, NC.
Reprints not available from the authors.
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|Author:||Javadzadeh, Barry; Means, Charles R.; Park, H. Kim|
|Publication:||Archives of Pathology & Laboratory Medicine|
|Date:||Aug 1, 2001|
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