Endonasal endoscopic resection of ossifying fibroma involving the ethmoid sinus, orbit and anterior skull base: case report and literature review.

Ossifying fibroma is a benign fibro-osseous tumour that rarely involves the ethmoid sinuses and orbit. It is classified as a benign fibroosseous lesion, a term that is synonymous with a variety of lesions reported in the literature. Recurrence rate with deleterious effects in cases of extramandibular ossifying fibroma is the impetus for open en bloc resection of the tumour. Continuously evolving techniques in endonasal endoscopic sinus surgery has rendered resection of large benign sinonasal and cephalonasal tumours possible. The authors report a case of ossifying fibroma involving the ethmoid sinus, orbit and anterior skull base in a 65-year-old previously healthy woman completely resected by endonasal endoscopic sinus surgery. The patient was free from postoperative complications and was dismissed from hospital on the sixth postoperative day. At present, the patient is disease-free at a regular five-year postoperative follow-up. Endonasal endoscopic resection of sinonasal ossifying fibromas is an excellent therapeutic option when performed by a surgeon experienced in endoscopic sinonasal surgery. The advantages of an endonasal endoscopic approach include direct visualization, enhanced visibility and magnification resulting in decreased intraoperative and postoperative morbidity. Aesthetic outcome is excellent in the absence of facial scars. © Copyright by Società Italiana di Otorinolaringologia e Chirurgia Cervico-Facciale, Rome, Italy.

Introduction

Ossifying fibroma (OF) is a rare, benign fibro-osseous tumour typically found in the mandible, and therefore has been reported mainly by oral surgeons . About 10% of all cases are found in the maxilla . OF rarely involve the ethmoid sinuses and orbit . The authors present an unusual case of OF involving the left ethmoid sinus, orbit and anterior skull base occurring in an elderly woman who was completely resected by endonasal endoscopic sinus surgery.

Case report

A 65-year-old previously healthy woman who presented with the sensation of pressure in the left orbit. She did not refer any disturbances of smell or vision. The patient was not taking any medications and had no known drug allergies. Ophthalmologic examination showed no pathologic findings. There was no conjunctival oedema or haemorrhage. The showed any pathologic changes.

Endoscopic evaluation of the left nasal cavity showed oedema within the left middle meatus. Multi-slice computed tomography (MSCT) of the paranasal sinuses demonstrated an ovoid mass expanding within the left ethmoid complex. On coronal MSCT, the tumour was seen to occupy the left nasal cavity and eroding the lamina papyracea. It was attached to the anterior skull base by a narrow, stalk like base (Fig. 1).

Fig. 1.

Preoperative coronal MSCT scan showing the tumour occupying the left nasal cavity and eroding the lamina papyracea. It was attached to the anterior skull base by a narrow, stalk-like base (black arrow).

Based on the physical examination findings and imaging studies, the patient was admitted to the hospital and prepared for surgery. The patient was operated under general, hypotensive anaesthesia. During the procedure, the tumour was found to be attached to the anterior skull base and eroding the left lamina papyracea. A 30° endoscope was used to proceed to delicate preparation of the anterior skull base. The tumour was completely resected endoscopically using straight powered drill bits with clear intraoperative presentation of cribriform plate. The intraoperative tumour is presented in Figure 2. The left periorbita and skull base were not surgically violated and orbital fat did not protrude into the surgical field at the end of procedure.

Fig. 2.

Intraoperative tumour specimen.

There were no postoperative complications. Routine postoperative endoscopic examination of the left sinonasal cavity was performed and no evidence of cerebrospinal fluid leaks from the anterior cranial fossa was present.

The histopathological finding was consistent with an OF. The tumour mainly consisted of two components: a fibrous stroma, rich in fibroblasts and small vessels surrounded with bony lamellae that were rimmed by osteoblasts and occasionally by osteoclasts.

A postoperative coronal MSCT scan after one year postoperative follow-up is shown in Figure 3. The patient is presently completely free of disease at a regular five-year follow-up.

Fig. 3.

Postoperative coronal MSCT scan at one year postoperative follow-up.

Discussion

OF holds a tenuous place in the classification of bony lesions. It was first mentioned by Menzel in 1872, who considered it to be a form of osteoma . OF is classified as a benign fibro-osseous lesion, a term that is synonymous with a variety of lesions reported in available literature (Table I).

Table I.

Various terms reported in the literature for different histological variations of ossifying fibromas.

Ossifying fibroma

Cementifying fibroma

Cemento-ossifying fibroma

Desmo-osteoblastoma

Psammo-osteoid fibroma

Psammonmatoid ossifying fibroma

Juvenile ossifying fibroma

Juvenile aggressive ossifying fibroma

Juvenile active ossifying fibroma

The origin of OF is debated with a predominant theory claiming the tumour originates from periodontal roots because of their capacity to produce cementum and osteoid tissue . The tumour has the capability of producing cement, lamellar bone and fibrous tissue in widely differing proportions. The periodontal membrane is a mesodermal germ layer product. The normal migration of the medial part of nasal anlage occurs through the ethmoid sinus region, and a small portion of this mesenchyme differentiates into the peridontal membrane . The ethmoidal localisation of OF could therefore be explained by incomplete migration and maturation of the peridontal membrane. Marvel et al. stated that OF originates from primitive mesenchymal cells that are believed to produce cementum at sites distant from odontogenic tissue .

Both benign and malignant fibro-osseous lesions should be considered in the differential diagnosis of OF. These include well-differentiated osteosarcoma, and the spectrum of fibro-osseous lesions of the head and neck .

Regardless of the theory of origin, fibro-osseous lesions and OF differ from fibrous dysplasia not only histologically, but also in their distinct clinical behaviour. Some authors have suggested that sharply defined calcifying spherulation is an important differential finding not seen in fibrous dysplasia, but most pathologists agree that it is very difficult to differentiate between these two entities using histological criteria alone. No hereditary tendencies have been observed, and no pigmentary or endocrine changes have been reported associated with ossifying fibromas. Moreover, abnormal serum calcium, phosphorous or alkaline phosphatase levels have not been reported.

OF is usually well circumscribed rather than diffuse and most often involves a single bone. The tumour produces moderate expansion of the tables of the involved bone, but usually leaves a thin "egg shell" boundary on either side with no periosteal reaction. It has definite boundaries but is not truly encapsulated . All previously mentioned features were present in our case.

OF typically presents in the mandible (75%) and thus is usually reported and treated by oral surgeons. Other reported locations of OF are maxilla, frontal bone, sphenoid bone, ethmoid bone, temporal bone, orbit, anterior cranial fossa and auricula -. The otolaryngologist's concern lies with the extramandibular presentation because OF is believed to behave more aggressively than its mandibular counterpart and requires complete surgical resection .

Presenting symptoms of OF depend on the location of the tumour and range from nasal obstruction to disfiguration. Individual patients may present with ophthalmologic symptoms, such as proptosis and diplopia. Intracranial extension of OF fibroma itself or associated mucoceles may give rise to neurological symptoms .

Patients with OF range from newborns to those in their eighth decade of life, with more aggressive behaviour at an earlier age -. The highest incidence of OF is reported between the ages of 20 to 40 years with a female predilection .

Although malignant transformation in OF has not been reported , surgery is the treatment of choice . Radiotherapy is contraindicated for OF because it may increase the possibility of malignant transformation. Reported rates of malignant transformation range from 4% to 40% .

Mandibular OF is traditionally treated with curettage because of the favourable results in this particular anatomical location. Recurrence rate with deleterious effects when OF is located in extramandibular regions is the impetus for open en bloc resection of the tumour . Complete resection of extramandibular OF is curative, and the exact surgical approach depends on the location and extent of the tumour. For the accomplishment of that task a variety of open approaches have been reported including: Caldwell-Luc operation, curettage, with peripheral ostectomy when the tumour is located in the floor of the maxillary sinus; lateral rhinotomy with medial maxillectomy when the tumour is located in the medial wall of the maxillary sinus; external ethmoidectomy for recurrent ethmoid tumour, transcranial/subcranial approach, and subfrontal approach .

Continuously evolving techniques in endonasal endoscopic sinus surgery have made resection of large benign sinonasal and cephalonasal tumours possible . A total of 15 cases of sinonasal OF endoscopically treated have been published in the available literature -. The advantages of endonasal endoscopic approach include direct visualisation, enhanced visibility and magnification resulting in decreased intraoperative trauma and postoperative morbidity. The advent of 3D navigation devices further enhances previously mentioned advantages. Aesthetic outcome is excellent in the absence of facial scars. Postoperative surveillance is accurate and flaw-less. All these features make an endoscopic approach a preferable option wherever possible. Complications of the endoscopic technique include injury to the skull base with resultant cerebrospinal fluid leak, infection, bleeding and injury to orbital structures .

Conclusions

In this report, we present a case of a 18 mm OF that was completely resected endoscopically without complications or recurrence after five-year follow-up. The tumour's well-demarcated borders allowed for complete resection and ensured assurance of tumour-free margins. The unusual feature of OF in our case was its adherence to the anterior skull base in the form of a narrow stalk and without dural involvement. It significantly complicated the operating procedure because of imminent endocranial complications. The tumour was successfully and completely drilled off from the skull base and further extracted through the choanae and mouth.

Endonasal endoscopic resection of sinonasal ossifying fibromas is an excellent therapeutic option when performed by a surgeon experienced in endonasal endoscopic sinus surgery. The endoscopic examination also provides excellent postoperative surveillance for early detection of recurrence. It should be anticipated as a treatment of choice in case of sinonasal OF with hesitation only in cases of extensive orbital or intracranial extension.