Juvenile ossifying fibroma: a case study

SAIZ-PARDO-PINOS AJ, OLMEDO-GAYA M-V, PRADOS-SÁNCHEZ E, VALLECILLO-CAPILLA M. JUVENILE OSSIFYING FIBROMA: A CASE STUDY. MED ORAL PATOL ORAL CIR BUCAL 2004;9:454-8

ABSTRACT

We present the case of an 8-year-old patient with a juvenile ossifying fibroma in the right mandibular angle and a radicular cyst in the left mandibular angle, which produced a major swelling at the level of the mandibular angles and prevented the correct eruption of the lower first molars. After the clinical and radiological (panoramic X-ray and dental scan of the mandible), the corresponding surgical treatment (cystectomy and remodelling) and histopathological study were carried out. Although juvenile ossifying fibroma is an uncommon clinical entity, its aggressive local behaviour and high recurrence rate mean that it is important to make an early diagnosis, apply the appropriate treatment and, especially, follow the patient up over the long term.

Key words: Juvenile ossifying fibroma, fibro-osseous lesions, aggressive ossifying fibroma, reticular desmo-osteoblastoma, radicular cyst.

INTRODUCTION

Juvenile ossifying fibroma (JOF) is an expansive intraosseous lesion of the jaw, comprising fibrous cell tissue that contains spheroid calcifications and randomly oriented irregular bone structures. It is presented by patients under 15 years old. Over time, lesions with this morphology have been variously described as juvenile ossifying fibroma (1), active juvenile ossifying fibroma (2), aggressive ossifying fibroma (3), reticular desmo-osteoblastoma (4) or active fibrous dysplasia (5).

They are non-odontogenic lesions that imitate odontogenic lesions (6).They are histologically characterised by the presence of fibrous stromal cells along with mineralised particles.

Clinically, it is a large asymptomatic tumour of aggressive appearance due to the bone destruction it produces. The lesion is not encapsulated, although it is well demarcated from the surrounding bone. The essential characteristics of this clinical entity are as follows: the early age of onset, the bone pattern, the high tendency to recurrence and the aggressive local behaviour (7). In the jaw, JOF is considered to develop from undifferentiated cells of the periodontal ligament, usually in the premolar and molar region.

The differential diagnosis with other fibro-osseous lesions of the jaw, such as cemento-ossifying fibroma, osteoid osteoma or bone dysplasia, should be made with a mandatory pathological study, and is largely based on the nature of the calcified products of the tumour (7).

The treatment consists of a simple surgical excision. Because they are well-differentiated lesions, they are not radiosensitive and radiotherapy is contraindicated because it can cause malignisation. The purpose of this article was to present a clinical case of JOF and to analyse its clinical, radiological and histological characteristics, in order to assist us in our daily practice to distinguish this clinical entity from other fibrous lesions and carry out the appropriate treatment. A minimum 5-year follow-up of these patients is essential.

CASE REPORT

An 8-year old boy with no general history of interest was referred by his dentist to the Oral Surgery and Implantology Masters Clinic of the School of Dentistry of Granada University in February 2001 for a bilateral tumour localised in the mandibular angles and with an evolution of several months.

The clinical examination revealed a bilateral swelling of the external cortical layer at the mandibular angles, which produced a facial asymmetry. It was painless to palpation. Initially, a panoramic X-ray was taken, which showed two independent and well-differentiated lesions. Thus, the left mandibular angle showed a rounded radiolucent image with osteosclerotic edges related to the first permanent molar in eruption, whereas the right mandibular angle showed a less well-defined radiolucent image (Figure 1). A computed tomography (CT) scan with coronal sections and tridimensional reconstruction was carried out to show the true extent of the lesion. The scan revealed two extensive tumours at the mandibular angles and a major periosteal reaction of the right side that may have been due to the rupture of the external cortical layer, as shown by octagonal sections 11 and 12 of the scan (Figure 2).

The patient underwent surgery under general anaesthesia. On the right side, there was a paracrestal approach to the attached gingiva, osteotomy ofthe vestibular wall of the mandible, resection of the fibrous tumour, which was hard and of fibrous consistence throughout its extension, and curettage of the remnant bone bed. On the left side, a cystectomy was performed, allowing physiological eruption of the lower left first molar.

The histopathological study revealed a neoformation of mesenchymal type in the right mandibular angle, composed of mature bone trabeculae and, less frequently, osteoid-type neoformation, leading to its diagnosis as a JOF (Figure 3). In contrast, the left mandibular angle showed the presence of a radicular cyst due to the cystic structure covered by flat multi-stratified epithelium that presented with oedema and exocytosis phenomena. The age of the patient and the close association with a permanent first molar in eruption suggested a paradental cyst or infected mandibular cyst. However, it was diagnosed as a radicular cyst because of the presence of caries in a deciduous molar and based on the histological study.

In conclusion, the post-operative follow-up at six months, one year and two years has demonstrated the benefit of the conservative surgical treatment, with excision of the fibroma and enucleation of the radicular cyst at the left mandibular angle (Figure 4). As a result of this approach, a progressive bone neoformation and consequent diminution of the initial radiolucent areas were observed. In addition, there was a physiological eruption of the molars that were initially seen to be affected by the lesions. Normal growth, mastication, aesthetics and mandibular neural function were preserved.

DISCUSSION

The main characteristics of juvenile ossifying fibroma are the early age of onset, the localization of the tumour, the radiological pattern and a tendency to recurrence.

As the term “juvenile” underlines, the tumour largely develops in children, 79% of whom are under 15 years old. (8). In reviews published by Hamner et al. (9) and Slootweg et al. (10) , the mean age of onset was 11.5 and 11.8 years, respectively. This characteristic was also observed in the present case of an 8-year old boy. In addition, lesions localised in the jaw are commonly associated with the eruption of permanent molars, as also occurred in our case.

Authors differ in their reports of the localization of the lesion. Slootweg et al. (10) and Makek (11) described the maxilla as the most frequent site, with Johnson et al. (12) even reporting that 90% of facial bone fibromas occur in the paranasal sinuses and only 10% in the mandible. On the other hand, Hamner (9), Leimola et al. (13), Brannon and Fowler (14) and Sánchez Cuéllar et al. (15) reported a mandibular predominance. According to most authors, there is no predilection for either sex, although Johnson et al. (12) found a higher incidence in females.

In general, JOF has a more aggressive growth compared with ossifying fibroma, which chiefly appears in the third and fourth decades of life. Most cases of JOF are asymptomatic, as is reflected in the present case, and the first clinical manifestation is a swelling of the mandibular cortical layer, which produces a marked extra-oral facial asymmetry. There is a tendency to aggressive growth, as shown by Hall et al. (16) and Zupi et al. (17), and also to recurrence, ranging from the 30% rate observed by Johnson et al. (12) to the 58% rate reported by Makek (11). Local recurrence is likely if the tumour is not completely removed, although it can also be caused by dysplastic processes in the bone metabolism. Nevertheless, it is important to perform a clinical and radiological follow-up for as many years as possible, because of the possibility of recurrence in this type of neoformation. Noffke (18) carried out a radiological follow-up of a mandibular JOF and found, at eight years of its enucleation, an aneurysmatic bone cyst and a reduction in the bone content.

Radiographically, the demarcation of the tumour from the surrounding bone is well-defined by a radio-opaque border, and this characteristic is important in the differential diagnosis between JOF and fibrous dysplasia, because the latter presents a radiographic image with a diffuse border. The radiolucency of the lesion varies, depending on the maturation stage and amount of calcification (19).

In the follow-up orthopantomography performed at one and two years, a favourable clinical evolution of the patient was observed, given that the permanent molars had erupted and no radiolucent areas could be seen in the mandibular angles where the JOF and radicular cyst had been enucleated.

ACKNOWLEDGEMENTS

The authors thank Dr. José Aneiros Cachaza for his invaluable collaboration in the histopathological study.

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