Bilateral Nonossifying Fibroma of the Mandible: A Case Report of a Rare Entity

Abstract

Nonossifying fibroma (NOF) is a benign lesion confined to the bone marrow and connective tissues without exhibiting osseous metaplasia. NOF of long bones in children is more common than its gnathic counterpart. Mandibular NOF is rare, and there is a paucity of information in the literature. NOF of the jaws clinically presents as a nodular, fibrous, asymptomatic, gingival, or alveolar mucosal enlargement, with or without facial swelling. NOF differs from the ossifying type by the presence of metastatic woven bone in ossifying type. This article reports an example of bilateral, multilocular, NOF of the mandible in a 15-year-old female patient with unilateral, asymptomatic facial asymmetry. The radiographic features were characteristic of NOF. It was treated successfully with surgical excision and curettage. A 2-year postoperative follow-up showed recurrence of the right lesion and needed secondary surgical intervention, and the tumor on the left side, however, healed well without recurrence.

INTRODUCTION

Nonossifying fibroma (NOF) was first reported in 1941 by Sontag and Pyle.^[1] It is classified as per the histologic classification of bone tumors by the WHO as a nonneoplastic tumor-like lesion.^[2,3] It was described as “nonosteogenic fibroma” by Jaffe and Lichtenstein in 1942.^[4] Fibrous cortical defect (FCD) and NOFs are synonymously used and represent the most common lesions of the skeletal system^[1,5] NOF is most commonly reported in long bones (33% of healthy children exhibit FCD),^[7] While the mandibular NOF cases are few.^[6,7] NOFs of the jaws are often seen in children of 10–15-year age group, whereas the long bone variant exhibits itself at an earlier age.^[8] Long bone NOF lesions show male predilection, while the mandibular lesions show female predilection. NOF of the jaws are asymptomatic or show diffuse swelling at the involved site.^[6,8–10] Histologic features show an abundance of fibroblasts laid on connective tissue matrix with giant cells and histiocytes.^[7] Traumatic irritation, dystrophic calcification, and growth disturbance are the probable etiologic causes of these lesions.

NOF can be associated with other skeletal anomalies such as Jaffe–Campanacci syndrome,^[11] Fanconi syndrome with osteomalacia, and others.^[11–13] Differential diagnosis includes fibromatosis, fibrous dysplasia, nonosteogenic fibroma, FCD, aneurysmal bone cyst, neurofibromatosis, cortical desmoid, enchondroma, eosinophilic granuloma, nodular fibrous oral lesions, desmoplastic fibroma, and fibroxanthoma. Surgical intervention is not recommended in nonexpansile, NOFs unless they tend to expand and show a tendency to fracture the involved bone. NOF may or may not be associated with neurofibromatosis.^[14,15] Although the typical radiographic features and clinical presentation of NOF suggest the condition, a definitive diagnosis is confirmed by histological examination.^[16] A treatment plan is based on the stage of NOF to prevent bone fracture. Staging or fracture risk assessment for NOF of the jaws can be referred from Ritschl^[17–19] fracture risk criteria. The author categorized fibrous metaphyseal defect of long bones accordingly: Stage A: a small, oval-polycyclic eccentric corticular lesion near the epiphyseal plate without a sclerotic border; Stage B: a polycyclic-shaped lesion with thin but clear sclerotic borders, thinning the cortex, usually away from the epiphysis, sometimes showing protrusion without periosteal reaction, resembling hourglass shape; Stage C: Stage A and Stage B resemble each other with diffuse sclerosis extending from diaphysis; and Stage D: total sclerosis of the lesion.

CASE REPORT

A 15-year-old female patient complained of pain in the lower right posterior teeth for the past 2 to 3 months. There was no clinical history of patients regarding trauma, medical illness, and gave no relevant familial history. On extraoral examination, a diffuse facial asymmetry [Figure 1] was noted on the left side with no remarkable facial enlargement on the right side. The swelling was nontender and firm on palpation. On intraoral examination, the tumor on the left mandible extended from the distal aspect of the first molar to the anterior border of the ramus of the mandible with vestibular obliteration. A similar finding was noticed with vestibular obliteration on the right lower posterior region of the mandible, extending from the distal of the first molar to the coronoid process. On intraoral palpation, swelling on the lower right side of the mandible was tender, whereas, on the lower left side, it was nontender. The growth on both sides had increased gradually in size. The teeth involved were not carious.

Figure 1: Preoperative photograph of a 15-year-old patient with NOF showing diffuse enlargement of the left side of the face. NOF: Nonossifying fibroma

Radiographic findings showed multilocular radiolucencies with mandibular buccal and lingual cortical bone expansion on the right and left sides, extending from the distal of the first molar to the coronoid process on the right and extending from the first molar to the ascending border of the ramus anteroposteriorly, expanding but not fracturing the buccal and lingual cortical plates mediolaterally with a resultant shift of the mandibular canal toward the lower border of the mandible, sparing approximately 1 cm of the lower border of the mandible. There was no resorption of the bone surrounding the roots of the involved teeth [Figures 2a, b, 3, and 4].

Figure 2: (a and b) CBCT and 3D reconstruction of the skull showing bilateral multilocular NOF. CBCT: Cone-beam computed tomography, NOF: Nonossifying fibroma

Figure 3: CBCT axial view. CBCT: Cone-beam computed tomography

Figure 4: Panoramic view

Treatment

Surgical excision and curettage of the lesion was done [Figure 5a and b].Post-op intraoral sutures and the excised NOF specimen is shown in Figure 6 and 7 respectively. However, NOF on the left side showed no recurrence [Figure 5a and b]. Postoperative healing was uneventful [Figure 8].

Figure 5: (a and b) Surgical excision and curettage

Figure 6: Excised specimen

Figure 7: Closure of the excision site with sutures

Figure 8: Wound healing at the site

Prognosis

Prognosis depends on the recurrence and extension of the expansile lesion with or without a bone fracture or intrusion on the adjacent vital structures. If the bone involved is medullary, without the involvement of peripheral bone, the prognosis is good. Some lesions show spontaneous regression without any surgical intervention.

DISCUSSION

Differential diagnosis

Radiologic findings of polyostotic fibrous lesions and NOFs display similar characteristics. Histological findings help in differentiating the two. Neurofibromatosis and NOFs share similar clinical characteristics. NOFs and congenital fibromatosis radiographically resemble each other, but the latter is more prevalent in the spine and ribs. Lymphangiomatosis and cystic hemangiomatosis of the bone involve diaphyseal bone and viscera, thus differentiating from NOF of the jaws. If a patient with neurofibromatosis exhibits multiple lytic lesions on the radiograph, it is suggestive of NOF. Since NOF and fibrous cortical bone defects show ossification defects, they cannot be strictly categorized as true neoplasms.^[20–22] FCDs and NOFs exhibit similar characteristics, but FCDs are smaller compared to NOFs radiographically. NOFs are synonymously called fibroxanthoma, FCD, or benign fibrous histiocytoma.^[11] NOF can be differentiated from odontogenic and nonodontogenic tumors clinically, radiographically, and histopathologically.^[23]

Associated syndromes/diseases

Extraskeletal congenital anomalies such as café-au-lait spots and other signs of neurofibromatosis, mental retardation, hypogonadism or cryptorchidism, ocular anomalies or cardiovascular malformations, Jaffe–Campanacci syndrome, fanconi syndrome with osteomalacia may be associated with NOF.^[11,12,24] Reports also show NOF association with congenital eye defects such as pigmentary dispersion of the retina, cataract, eyelid malformation, papillary collaboma, dermolipoma of the conjunctiva, alopecia, kyphoscoliosis, precocious puberty, megaureter, epiphysiolysis, and knee deformities.^[24,25] Cardiovascular defects associated with NOF include aortic isthmus, stenosis, and mitral insufficiency. 6.7% of nonsyndromic NOFs showed recurrence in comparison with a higher rate of about 60% recurrence in syndromic NOFs.^[26] Syndromic forms are, however, less prevalent than nonsyndromic counterparts.^[26]

Treatment options

Treatment options depend on the presentation of the tumor. Its association with syndromes shows high chances of recurrence, thus calling for a vigorous surgical removal with curettage and bone graft.

CONCLUSION

A sound clinical-histopathological knowledge of the lesion helps in differentiating rare NOF of the jaws from similar jaw lesions. Timely surgical intervention helps in preventing pathological fracture of the jaws. Surgical excision with curettage and bone grafting, if needed, is the treatment of choice.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.