Benign Fronto-Orbital Osteoblastoma Arising from the Orbital Roof: Case Report and Literature Review Ali Akhaddar, M.D.,* Miloudi Gazzaz, M.D.,* Mouna Rimani, M.D.,† Brahim Mostarchid, M.D.,* Ahmed Labraimi, M.D.,† and Mohamed Boucetta, M.D.* *Department of Neurosurgery and †Pathology, Mohamed V Military Hospital, Rabat, Morocco
mation. Twelve previously reported cases were also reviewed. © 2004 Elsevier Inc. All rights reserved.
Akhaddar A, Gazzaz M, Rimani M, Mostarchid B, Labraimi A, Boucetta M. Benign fronto-orbital osteoblastoma arising from the orbital roof: case report and literature review. Surg Neurol 2004;61:391–7.
Anterior cranial fossa, orbital tumor, osteoblastoma, osteoma, proptosis, skull base tumor.
Osteoblastoma is an uncommon benign osteogenic neoplasm that rarely involves the orbit. Intracranial and intraorbital extension causing neurologic and ophthalmologic symptoms and signs is very unusual. We report the case of an osteoblastoma of the orbital cavity with ethmoidal and anterior cranial fossa extension presenting as unilateral proptosis. Manifestations and management of this rare fronto-orbital lesion are discussed, and the relevant literature is reviewed. CASE DESCRIPTION
This 22-year-old man experienced a 3-month history of progressive left proptosis without neurologic symptoms. Computed tomography and magnetic resonance imaging scans demonstrated a bony mass involving the roof of the left orbit and extending laterally to the adjacent ethmoid cells and upward to the lower part of the homolateral frontal convexity without parenchymal abnormality. A presumptive diagnosis of osteoma was considered. A left fronto-orbital craniotomy was performed. At surgery, the tumor was well circumscribed by a sclerotic margin. It was granular with bony spicules, destroying the orbital roof and involving the orbital cavity, ethmoidal cells, and anterior cranial fossa. The lesion was totally removed, and the anterior cranial base reconstructed. The histologic features were typical of benign osteoblastoma. After a follow-up period of 12 months, the patient has remained well without evidence of recurrence. CONCLUSION
Osteoblastoma should be considered in the differential diagnosis with other fronto-orbital bone-forming lesions. Although generally regarded as benign, a complete resection is recommended to prevent the possibility of postoperative recurrence and malignant transfor-
Address reprint requests to: Dr. Ali Akhaddar. M.D., 34, Rue Oued Ziz, Apartment n° 7, Agdal 10000, Rabat, Morocco. Received January 23, 2003; accepted April 4, 2003. © 2004 Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010 –1710
steoblastoma (OTB) is an uncommon benign bone neoplasm that usually develops in the vertebral column and in the long tubular bones (60% of cases) [1,15]. Skull involvement is rare (less than 20%) where it is encountered with a predilection for the mandible, facial bones, and temporal bones [5,16,17,21]. The orbit is much less frequently involved. To our knowledge, there have been about 16 reported cases, and among them we could find only 12 presentations with skull base extension [2,3,7,9,13,16,18,22,24,26 –28]. We report a new case of benign osteoblastoma of the orbital roof with orbital, ethmoidal, and subfrontal extension producing exophthalmos. Previously published data are also reviewed.
Case Report The patient, a 22-year-old man, was admitted to our department with a 3-month history of gradually painless proptosis of the left eye. He denied any visual changes, decrease in acuity, or loss of visual fields. Four months before admission, he began to experience progressive minor frontal headaches that were alleviated by simple analgesia. He had no history of trauma or surgery and overall his medical records were unremarkable. An ophthalmological examination performed at admission revealed that the left eye was proptosed 0090-3019/04/$–see front matter doi:10.1016/S0090-3019(03)00455-5
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(4 mm). The left extraoccular movement was restricted in both upward and medial directions, but visual acuity was normal in both eyes with no alteration of anterior segment and fundus. There were no abnormalities in both physical and blood examinations. Coronal and axial computed tomography (CT) scanning revealed a well-circumscribed hyperdense mass that invaded the left orbital roof with intraorbital, ethmoidal, and anterior cranial fossa extension interpreted as osteoma (Figure 1A). Using bone windows, this mass had a small-dense cortical margin with a more radiolucent central zone suggesting a mixture of bone and fibrous tissue (Figure 1B). There was no evidence of frontal sinus erosion. Magnetic resonance imaging (MRI) in the axial, sagittal, and coronal planes demonstrated a homogeneous extraconal mass with iso-low signal intensity on T1-weighted imaging. The lesion had a signal void on T2-weighted imaging. However, there were small areas that appeared to have high signal intensity. MRI was important in the evaluation of intracranial and intraorbital extension, demonstrating superior displacement of the left frontal lobe and downward displacement of the left optical nerve and eyeball. The frontobasal dura and the periorbital tissues appeared intact (Figure 2A, B). A left-sided subfrontal approach with extradural exposure of the anterior skull base was performed. After reclination of the frontal dura, the tumor was disclosed; it was granular, vascular with bony spicules, and had no capsule but was well circumscribed by a tiny shell of bone. Only a slight adhesion to the dura matter was seen and repaired using a patch of galea and fibrin glue. The tumor involved the two-third posterior portion of the orbital roof and the superior portion of the left medial orbital wall with some extension to the adjacent ethmoidal cells. A plane of cleavage with the posterior wall of the frontal sinus was identified. Moderate bleeding was controlled using bone wax. The orbital structure was well preserved but displaced inferolaterally by the tumor. Complete macroscopic removal of the lesion was achieved. The defect of ethmoidal cells was patched with a pericranial graft, and the orbital roof was reconstructed with autologous bone from the internal surface of the frontal bone flap. Microscopically, the lesion was composed by a fibrovascular stroma with numerous osteoblasts, osteoid tissue, well-formed woven bone and giant cells. Most of the bony trabeculae were rimmed by osteoblasts. There was no evidence of malignancy.
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Operative and histopathological findings confirmed the diagnosis as a benign osteoblastoma (Figure 3). Both in the immediate and late postoperative periods, the patient made an excellent recovery. His proptosis speedily resolved and his visual acuity and ocular movements remained intact. Postoperative CT scan images showed no residual tumor (Figure 4). There has been no recurrence in the past 12 months.
Discussion OTB was first recognized as a pathologic entity in 1956 by Jaffe  and Lichtenstein . It is a rare osteoblastic tumor, representing 1% of all primary bone tumors and 3% of all benign bone tumors. Approximately 60% of OTB are situated in the vertebral column and long bone of the extremities . In rare instances, OTB arise in cranial locations; in one series of 98 OTB, only 3 were found to involve the skull . In the orbit, about 15 cases [2–5,7,9,10,12,13,16,18,22,24,26 –28] of osteoblastoma have been reported since the first citation by Dahlin in 1967 . This tumor involved the orbital roof, but no other details were given. To our knowledge 80% of orbital OTB affected the skull base. Table 1 summarizes 13 well-documented and histologically verified cases of orbital OTB with skull base extension [2,3,7,9,13,16,18,22,24,26 –28], including the present case. OTB developing in the orbit may secondarily invade the ethmoidal cells (n ⫽ 6), sphenoid bone (n ⫽ 3), maxillary (n ⫽ 3), or frontal (n ⫽ 1) sinus. All cases have an anterior skull base extension except one with middle cranial fossa involvement . Young people were usually affected, as in our case, but the tumor may appear at any time from 3 to 76 years (mean age of 24 years) without sex predilection (6 female for 7 male patients). The lesion usually grows slowly but sometimes shows rapid growth as in our case (3 months) simulating infectious or malignant process. The mean duration of symptoms was 18 months. In 1983, Berciano  reported a huge intracranial OTB having over 60 years symptoms duration with blindness. Generally, patients complain of a growing mass or pain. In the orbit, the tumor causes a progressive painless proptosis without pulsation or bruit and tend to expand downward into the orbit, displacing the globe. Exophthalmos (n ⫽ 9), supra or periorbital swelling (n ⫽ 6), frontal headache (n ⫽ 3), and visual loss (n ⫽ 3) are the most common clinical features. When the tumor extends to the skull base, other cranial nerve deficits may occur ). Nasal
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CT scans without contrast medium. Preoperative axial (A) and coronal [bone windows] (B) images showing a well-circumscribed calcified mass invading the left orbital roof with intraorbital, ethmoidal, and anterior cranial fossa extension. The frontal sinus was not eroded. There was a right maxillary sinusitis.
obstruction , epileptic seizures, and manifestation of increased intracranial pressure are exceptional . There was no preferential side of pre-
sentation, and no specific factors have been identified. On histopathological examination, all of the tu-
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Preoperative MRI scans. Nonenhanced T1-weighted sagittal (A) and T2-weighted axial (B) images revealing a homogeneous mass on the left orbital area with superior displacement of the frontobasal lobe and downward displacement of the left eyeball.
mors were considered benign. OTB appear to be composed of small irregular bony trabeculae and osteoid separated by a vascular stroma. The trabecular bone is usually surrounded by numerous osteoblasts, and some giant osteoclastic cells are present in the fibrous stroma [1,7,12,15]. The rich vascularity of the fibrous stroma accounted for severe bleeding during some surgical procedures [2,27]. Histologic differentiation with osteoid os-
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teoma can be difficult, but the latter is usually more painful, smaller than 20 mm and seems to have a more-defined sclerotic border [15,25]. Neuroradiologic examination is particularly important to make a preoperative diagnosis. The imaging modality of choice is CT scanning with bone windows and MR imaging. Although OTB may be detected on some plain X-rays as a cystic bone lesion with sclerotic margin [18,28], such films do not give sufficient detail. On CT scan (n ⫽ 11), the lesion appears well circumscribed with high bone density but less dense and less homogenous than osteoma [4,8]. This slow-growing benign tumor pushes the surrounding bone without real bone erosion, as in our case. Reports of MRI findings are quite few (n ⫽ 3). The tumor generally tends to show a low-signal intensity on both T1- and T2weighted studies without gadolinium enhancement [2,13]. In our case, the tumor was unusually isohypointense in T1-weighted images, with some small areas within the lesion that appeared to have high signal intensity in T2-weighted images suggesting a mixture of bone and fibrous tissue. Orbito-frontal OTB should be differentiated from other similar slow-growing bone tumors, such as osteoma , osteosarcoma , osteoid osteoma , ossifying fibroma , calcifying meningioma , giant cell tumor , aneurysmal bone cyst , and fibrous dysplasia . Careful radiologic evaluation coupled with clinical findings allows differentiation among these lesions. When used, bone scanning (technetium-99) revealed a “hot” area [13,28]. Angiography and preoperative embolization are helpful to reduce bleeding during surgery in some OTB . Total surgical resection is the treatment of choice of OTB. In the orbit, osteoblastoma was removed by various surgical approaches in previous ophthalmologists’ reports [18,22]; however, complete removal of this tumor is difficult when there is a cranial base extension. An anterior skull base approach has been advocated by all neurosurgeon authors [2,7,8,26 –28]. The choice of surgical approach is made on the basis of tumor site and size as documented by CT and MR scanning. As in our case, a frontal osteoplastic bone flap via a coronal incision provided good access to all tumors of the orbital roof with orbital and anterior cranial fossa extension . Using a large cranio-orbito-facial degloving approach (dismaking flap), Imai et al  resected a nasal osteoblastoma completely, even though it extended into the orbit, the maxilla, and the anterior cranial fossa. Reconstruction of the anterior wall of the frontal sinus, orbital roof, and anterior cranial base was sometimes required using
The section shows bony trabeculae rimmed by osteoblasts. The fibrovascular stroma was associated with numerous osteoblasts, osteoid tissue, well-formed woven bone, and giant cells (H&E ⫻ 400).
either acrylic materiel or autologous bone. To prevent meningitis and cerebrospinal fistula, the dura must be closed hermetically using patches of galea and fibrin glue . A lateral rhinotomy with external ethmoidectomy had been used in a case of orbital OTB involving paranasal sinuses . Prognosis after complete removal is uniformly good. Among 13 cases, there was no serious permanent postoperative deficit and no postoperative death. Only 2 cases [18,28] have demonstrated recurrence at one year and 7 years after the first excision, respectively (because of incomplete re-
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moval). Parodi et al  reported a case with partial ablation but recurrence was not observed 4 years postoperatively. No malignant transformation was seen. Adjuvant radiotherapy for residual OTB is still controversial [2,7,16]. Radiation therapy is reserved for some cases in which only subtotal resection has been achieved or for unresectable lesions in symptomatic patients. Although generally regarded as benign, a continuous follow-up is necessary to detect any recurrence or malignant transformation [5,11,15,22].
Postoperative axial CT scan, showing neither residual tumor nor eyeball displacement.
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Summary of Cases of Orbital Osteoblastoma with Skull Base Extension in the Literature Including Our Case
PATIENT DURATION PATIENT AUTHORS (REF. AGE (YR)/ OF NO. NO.) SEX SYMPTOMS 1. 2.
Shepherd et al, 1977  Berciano et al, 1983 
Clutter et al, 1984 
Lowder et al, 1986 
Leone et al, 1988 
Vara-Thorbeck et al, 1990 
Ciappetta et al, 1991 
Parodi et al, 1993  Snow et al, 1994 
Ungkanont et al, 1996 
Imai et al, 1997 
Batay et al, 1998 
Akhaddar et al, 2003 (present study)
Rt Exo, Frontal Frontal sinus, headache Orbit Rt Exo, ACF, Ethmoid, Blindness, Sphenoid, Seizures Maxillary sinus, Orbit Lt supraorbital Orbital roof, swelling Supraorbital ridge Lt supraorbital Orbital roof, swelling ASB Rt Exo, Ptosis, Orbital roof, Diplopia ASB Periorbital swelling Painful Rt Orbital roof, Frontal ACF swelling Lt Exo, Sphenoid bone, Photophobia, MCF, Orbit Painful Lt Exo, Orbit, Ethmoid, Blindness Frontal bone Rt Exo Ethmoid, Supraorbital area Rt Exo, Nasal Ethmoid, Orbit, obstruction Sphenoid and Maxillary sinus, Nasal cavity Lt medial Nasal, Ethmoid, canthus Maxillary swelling sinus, Orbit, ACF Lt Exo, Orbital roof, Supraorbital ACF mass Lt Exo Orbital roof, ACF, Ethmoidal cells
Frontal craniotomy, 18 mo Total resection Not operated Died
n.d., Total curretage
Transcranial recurr. 1 yr approach, later reop. Piecemeal 4 yr excision Frontal craniotomy, 10 mo Total resection Frontal craniotomy Recurrence 7 yr later reop. 6 mo n.d., Total removal 2 yr Orbital approach, 4 yr Partial removal Frontal craniotomy, Total removal Rhinotomy lateral Total removal
Dismasking flap, Total removal
n.d., Total removal 44 mo Frontal craniotomy, 12 mo Total removal
ACF, anterior cranial fossa; ASB, anterior skull base; Lt, Left; MCF, medial cranial fossa; n.d., no data; Rt, Right; Exo, exophthalmos.
Conclusions Orbital osteoblastoma is an uncommon tumor that rarely affects the skull base. It should be included in the differential diagnosis of other expansive cranial bone-lesions. Although not pathognomonic, a wellcircumscribed calcified mass with a thin cortical margin and a decreased signal on both T1- and T2-weighted images should be considered for the diagnosis. CT bony windows and MRI are especially
important in the evaluation of such lesions in the preoperative period. A fronto-orbital craniotomy is recommended for exposure of the tumor and plastic repair of the anterior cranial base. The prognosis is related to the quality of surgical resection. Although generally regarded as benign, osteoblastoma has potential for recurrence, local invasion, and malignant transformation.
The authors thank Fatiha-Hiba Chayeb for her secretarial assistance in the preparation of this manuscript.
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The authors present a case of benign osteoblastoma in a young man. It is well written and presents previously published cases. Benign osteoblastomas are very rare and account for less than 1% of primary bone tumors. They most often involve the vertebrae and small bones of the hands and feet. The tumor affects younger males more prevalently. The aim of the surgery should be total removal of the tumor. When it is so, the tumor can be curable even without adjuvant irradiation and chemotherapy. Prof. Dr. Yucel Kanpolat Department of Neurosurgery Ankara University School of Medicine Ankara, Turkey