Benign osteoblastoma of the mandibular ramus: Review of the literature and report of a case

Benign osteoblastoma of the mandibular ramus: Review of the literature and report of a case

1310 BENIGN OSTEOBLASTOMA OF THE MANDIBULAR RAMUS J Oral Maxillofac Surg 58:1310-1317, 2000 Benign Osteoblastoma of the Mandibular Ramus: Review of...

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BENIGN OSTEOBLASTOMA OF THE MANDIBULAR RAMUS

J Oral Maxillofac Surg 58:1310-1317, 2000

Benign Osteoblastoma of the Mandibular Ramus: Review of the Literature and Report of a Case Maha Shawky Ahmed, MSc, PhD,* and Alagumba L. Nwoku, MD, DMD, PhD† Benign osteoblastoma is a rare primary bone tumor that was first recognized as a distinct neoplasm by Lichtenstein1 and Jaffe2 in the same year, 1956. It is a vascular osteoid and bone-forming benign tumor characterized cytologically by the abundant presence of osteoblasts. It constitutes approximately 1% of all primary bone tumors.3-6 The sites of predilection for the tumor are the long bones, vertebral column, and small bones of hands and feet. Its occurrence in the skull and jaw bones is relatively rare and represents only 15% of all osteoblastomas.6 The tumor shows a sex predilection for males and constitutes less than 1% of all tumors of the maxillofacial region.7 The mandible is affected more frequently than the maxilla,8 with 90% of cases arising in persons younger than 30 years of age, with an average of 17 years.6 At sites other than the skull and jaw bones, the sex and age distribution of benign osteoblastoma is equal.9 The first case of benign osteoblastoma of the jaws was reported by Borello and Sedano10 in 1967. Clinically, it is characterized by swelling, pain, and erosion and expansion of the bony cortex, depending on the site and size of the lesion.1,11-17 The tumor consists of a proliferation of abundant plump osteoblasts forming trabeculae of osteoid and immature bone in a wellvascularized stroma with numerous multinucleated cells adjacent to the osteoid trabeculae.12,14 The radiographic appearance is extremely variable and, de-

Received from the Division of Oral and Maxillofacial Surgery, Division of Maxillofacial Surgery and Diagnostic Sciences, King Saud University, College of Dentistry, Riyadh, Kingdom of Saudi Arabia. *Professor. †Professor and Head. Address correspondence and reprint requests to Dr Ahmed: Department of Oral and Maxillofacial Surgery, Cairo University, College of Oral and Dental Medicine, Cairo, Egypt; e-mail: [email protected] © 2000 American Association of Oral and Maxillofacial Surgeons

0278-2391/00/5811-0020$3.00/0 doi:10.1053/joms.2000.16637

pending on the degree of calcification in the lesion, it may appear radiolucent or semiradiolucent with radiopaque mottling and a well-demarcated margin. This report describes a case of benign osteoblastoma in a rare site, namely, the subcondylar region of the ramus of the mandible. It is presented with special reference to its differential diagnosis from the clinical, radiologic, and histologic aspects. A 1991 review of the literature listed only 45 cases of osteoblastoma of the maxillofacial region since 1967.17 Eight cases, including this one, are added to the previously documented cases in this review and report.

Report of Case A 17-year-old boy was seen in the oral and maxillofacial clinic suffering from dull pain and swelling on the right side of his face of 2 months’ duration. The pain was a constant dull ache that was exacerbated by function. He gave a history of trauma to the right ear with fracture of the ear cartilage at 2 years of age, as reported by the parents, and a second trauma to the face with fracture of the nasal bone when he was 9 years old. There was nothing else remarkable about the patient’s medical history. He was healthy, and a review of systems was noncontributory. Clinical examination showed a firm, painful swelling located in the right cheek involving the preauricular area and causing expansion of the buccal cortical plate and slight facial asymmetry (Fig 1). The swelling was relatively demarcated, tender, and approximately 2 ⫻ 1.5 cm in size. The overlying skin was of normal color and texture, with no evidence of paresthesia. The submandibular and cervical lymph nodes were not palpable. There was no limitation of mouth opening (42 mm), and no tenderness or crepitation in the temporomandibular joint. There was a scar behind the right ear and on top of the nose, which were consistent with the earlier history of trauma to these areas. Intraorally, the swelling was not visible nor palpable. A panoramic radiograph showed a well-defined, elliptical semi-radiolucent lesion containing faint to dense irregular radiopaque foci located at the base of the right condyle in the subcondylar region of the right ramus (Fig 2). The lesion was well delineated, with a thin sclerotic margin. In the mandibular midline, an impacted right canine was located close to the lower border of the mandible, and a small radiopaque mass was seen below the retained deciduous

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FIGURE 1. A 17-year-old boy at clinical presentation. Note the enlargement of the right preauricular area, causing slight facial asymmetry secondary to tumor expansion.

right canine that was interpreted as a supernumerary tooth. Two radiopaque foci were also discernible in the lower right canine-premolar area and the lower left second molar region (Fig 2). A posteroanterior radiograph showed expansion of the buccal cortical plate in the subcondylar region (Fig 3). A computed tomography scan showed a small hypoechoic focus involving the buccal aspect of the subcondylar region measuring approximately 0.74 ⫻ 0.71 cm. A small focus of density was seen in the inner lateral wall of the lesion that appeared to be represent a speckled pattern of calcification. Some degree of sclerotic change was noted adjacent to the lesion (Fig 4). A clinical diagnosis of fibroosseous lesion or tumor of bony origin was made. The patient was admitted to the hospital, and an operation involving complete local excision and curettage of the lesion was performed under general anesthesia through a small preauricular incision. The parents did not consent to the surgical removal of the embedded canine and excision of the other lesions; their main concern was treatment of the tender swelling causing the facial asymmetry and alleviation of the pain. The surgical specimens consisted of irregular pieces of hard and soft tissue (Fig 5). The soft tissue specimen was light brown, measuring approximately 1.5 ⫻ 0.8 ⫻ 0.5 cm, and the overlying thin, bony specimen was grayish, measuring approximately 1.6 ⫻ 0.1 ⫻ 0.5 cm. The surgical

FIGURE 2. Preoperative panoramic radiograph showing a well-demarcated semi-radiolucent lesion in the right subcondylar region.

FIGURE 3. Preoperative posteroanterior radiograph showing lateral expansion of the bone in the subcondylar region.

specimens were submitted for microscopic examination and routinely processed. The patient made an uneventful recovery and clinical and radiographic examination showed no signs of recurrence 1 year postoperatively, no disturbance in sensory function, and totally improved facial symmetry. Microscopic examination of representative slides from the specimen showed a predominantly cell-rich connective tissue stroma inside which were interdigitating trabeculae of osteoid and poorly calcified mineralized bone. The spindle-shaped stromal fibroblasts and plump osteoblasts appeared very active. Osteoblasts rimmed the borders of some of the trabeculae. Multinucleated giant cells were present in the stroma contiguous to the trabeculae, lying in lacunae at the border of the osseous structures. In some areas the histologic picture appeared pagetoid, with prominent reversal lines. A moderate number of tortuous, elongated capillaries are present. In some areas, focal perivascular inflammation was clearly seen (Fig 6).

Discussion Benign osteoblastoma is a rare tumor of the jaw bones. Histologically it shows proliferation of plump osteoblastic cells forming trabeculae of osteoid and

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FIGURE 4. A, Coronal CT image showing posterolateral involvement of the right subcondylar region. B, CT image in an axial projection showing lateral and medial expansion caused by the tumor.

immature bone in a loose, well-vascularized stroma. In all cases, there is a predilection for males, and most of the cases occur in young patients with a site predilection for the mandible.6 The first case of benign osteoblastoma of the jaws was reported by Borello and Sedano10 and was located in the maxilla. El Mofty and Refai8 reviewed 26 cases in 1989, and in 1990 Strand-Pettinen et al16 reported 33 cases and added one of their own. Asada et al17 in 1991 reviewed the recent literature and surveyed 45 cases of benign osteoblastoma of the jaw bones. Colm et al,18 in 1988, Haug et al7 in 1990,

FIGURE 5. Gross appearance of the surgical hard and soft tissue specimens.

Strand-Pettinen et al16 in 1990, Svensson and Isacsson19 in 1993, and Ataoglu et al20 in 1994 reported 1 case each. These 5 cases were located in the mandible. The case presented here adds to the number of benign osteoblastomas found in the mandible. A case in the maxilla was described by Ohkubo et al,21 and 1 in the retromaxillary region was reported by Guest and Juniper22 (Table 1). All previously reported cases occurred as isolated or solitary lesions, with the exception of 2 cases with multicentric occurrence7,17 (Table 1). The clinical presentation of benign osteoblastoma commonly features swelling and pain.6,10,13,23,24 However, 5 asymptomatic cases16,17,25-27 have been reported, some of which were detected on routine radiography. Computed tomography is a useful adjunct to the diagnosis and is of great value in determining the extent of the tumor as well as the degree of calcification. Scintigraphy also has been reported to be of some value in the diagnosis of these lesions.28 However, because radioisotopic bone scanning merely shows bone activity in a lesion that could be either osteoblastic or osteolytic, and which can occur in various fibro-osseous lesions and bony tumors, the

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FIGURE 6. A, Medium-power histologic view of a representative field of the surgical specimen. The poorly mineralized trabeculae interdigitate and have broad seams of osteoid. The connective tissue is cellular and well vascularized (H&E, original magnification ⫻100). B, Osteoblastic rimming, osteoclasts, and plump stromal fibroblasts and osteoblasts are seen around the trabeculae of poorly mineralized osteoid. Reversal lines are also evident (H&E, original magnification ⫻100). C, Multinucleated osteoclasts are seen in their lacunae in 2 poorly mineralized trabeculae (H&E, original magnification ⫻200). D, In this view, the peripheral osteoid lines relatively normal trabeculae. There are plentiful osteoblasts and numerous multinucleated giant cells. The stroma is cellular and fibrous, but loose-textured in some areas (H&E, original magnification ⫻100).

results obtained from this modality are not considered specific nor sensitive. In the current case, the patient had a constant, dull, aching pain of 2 months’ duration. Benign osteoblastoma of the maxillofacial region has been reported to present earlier than in other sites, with a maximum duration of 2 years.14 Fifty-three cases were reviewed in the current study, of which only 3 cases appeared in the temporomandibular joint7,15,19 area and another 3 cases involved the coronoid process of the mandible.7,27-29 In our case, the tumor was located in the subcondylar region of the superior ramus, and was well defined radiographically. This was in agreement with most cases of osteoblastoma reported in the mandible, which are relatively well demarcated compared with the maxillary cases.17 Treatment of osteoblastoma with local conservative excision and curettage should be adequate. The surgical approach for complete removal of the tumor has always been variable, depending on the tumor size and site, although in some cases the access had been potentially severely mutilating.22 Spontaneous regression of benign osteoblastoma has also been

reported,24,30 particularly in young patients (6 to 7 years of age) and when a history of trauma is contributory. Local excision and curettage of the tumor was performed in this case, and from the operative findings, it was clear that the tumor was completely removed and the surgical defect was eventually replaced by normal radiographically appearing bone (Figs 7, 8). Histologically, the most pathognomonic features are the presence of islands of osteoid tissue undergoing varying degrees of calcification and considerable osteoblastic activity in a loose, well-vascularized stroma. This was observed in this tumor, which showed predominantly a loose vascular stroma with scattered osteoid trabeculae and immature bone, abundant, plump, active osteoblasts, mild to moderate numbers of multinucleated giant cells, and scanty chronic inflammatory cells adjacent to the vascular spaces. No abnormal mitotic figures or cellular atypia were detected. A history of trauma was elicited in this case. Similar cases15,17,24,31-33 have been reported, which indicates that although benign osteoblastoma is widely consid-

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Table 1. CLINICAL AND RADIOGRAPHIC FINDINGS IN REPORTED CASES OF BENIGN OSTEOBLASTOMA Case

Author(s)

Year

Age

Sex

Location

Trauma

Symptom

Maxilla Mandible Coronoid Maxilla Mandible Mandible Mandible Mandible Mandible Coronoid Maxilla Maxilla Mandible Mandible Mandible Mandible Maxilla Mandible Mandible Mandible Maxilla Mandible Mandible Mandible Maxilla Mandible Mandible Maxilla Maxilla Mandible Maxilla Mandible Mandible Mandible Mandible Maxilla Mandible Mandible Maxilla Mandible Mandible Mandible Condyle Mandible Maxilla Maxilla rtMandible ltMandible Maxilla Mandible Superior ramus condyle, coronoid Mandible Retromaxillary area Condyle Mandible Subcondylar region

? ⫹ ? ? ? ? ? ? ⫹ ? ? ? ⫺ ? ? ? ⫺ ⫺ ⫺ ? ? ? ? ? ⫺ ? ? ? ? ? ⫹ ? ? ⫺ ? ? ⫹ ? ? ? ? ? ⫹ ? ? ? ⫹ ⫹ ⫹

Swelling Painful swelling None Tender swelling ? Painful swelling Painful swelling Painful swelling Painful swelling Painful swelling Painless swelling Painful swelling Tender swelling Painless swelling Tender swelling Tender swelling Swelling Swelling Painful swelling Tender swelling Painful swelling Painful swelling Tender swelling Painful swelling Painful swelling Tender swelling Painful swelling Swelling toothache Swelling Tender swelling Painful swelling Painful swelling Painful swelling Pain Painful swelling Painful swelling Painful swelling Painful swelling Pain Painful swelling Tender swelling Swelling Tender swelling Painful swelling Painful swelling Swelling Swelling none none Painful swelling

Radiopaque Radiolucent Radiolucent Radiopaque/-lucent Radiolucent Radiopaque/-lucent Radiopaque ? Radiopaque Radiopaque Radiolucent Radiopaque/-lucent Ground glass ? Radiopaque Radiolucent Radiopaque Ground glass Radiopaque ? Radiopaque ? Radiolucent Radiopaque Soft tissue shadow Radiopaque Radiopaque Radiopaque ? Radiolucent Radiopaque/-lucent Radiopaque/-lucent Radiolucent Radiopaque/-lucent Radiopaque Radiopaque Radiolucent Radiopaque/-lucent Radiopaque/-lucent Radiolucent Radiopaque/-lucent Radiopaque/-lucent Radiopaque/-lucent Radiolucent Radiopaque Radiopaque/-lucent Ground glass Ground glass Hazy Radiolucent

? ? ? Well-defined Well-defined Well-defined ? ? Well-defined Well-defined ? Well-defined ? Well-defined Well-defined ? Poorly defined Poorly defined ? ? ? ? ? Well-defined Well-defined Poorly defined ? ? ? Well-defined Well-defined Well-defined Well-defined Well-defined Well-defined Well-defined Poorly defined Well-defined ? Poorly defined Well-defined Poorly defined ? Well-defined Ill-defined Well-defined Well-defined Well-defined Poorly defined Well-defined

Painless swelling Painful swelling Painful swelling Painful swelling Painful swelling

Radiolucent Radiopaque/-lucent Radiolucent Radiopaque/-lucent Radiopaque/-lucent

Well-defined Poorly defined Poorly defined Well-defined Well-defined

1* 2 3 4* 5 6 7 8 9* 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44* 45 46 47†

Borello & Sedano Kramer Kopp Kent et al Akasaka et al Ito et al Brady & Browne Brady & Browne Smith Ito et al Wickenhauser et al Yip & Lee Hsu Remagen & Prein Kazama et al Takigawa et al Labayle et al Nagumo et al Farman et al Sakota Sakota Sakota Sakota Sakota Chatterji et al Greer & Berman Larsson et al Nyuu et al Nyuu et al Tanaka et al Hatakeyama & Suzuki Nowparast et al Danielidis et al Miller et al Miller et al Miller et al Sidhu et al Monks et al Smith et al Smith et al Shatz et al Eisenbud et al Weinberg et al Colm et al18‡ Ohkubo et al21‡ El-Mofty & Refai Asada et al

1967 1967 1969 1969 1971 1971 1972 1972 1972 1973 1973 1974 1975 1975 1976 1976 1976 1976 1976 1977 1977 1977 1977 1977 1978 1978 1978 1978 1978 1979 1979 1979 1980 1980 1980 1980 1980 1981 1982 1982 1986 1987 1987 1988 1989 1989 1990

21 6 19 13 18 18 19 14 7 19 5 22 23 15 20 16 15 37 9 33 19 21 37 18 30 30 15 52 17 6 14 14 15 37 6 26 13 19 21 15 17 11 19 35 6 11 38

M F M F M M M M M F M F F M F M F M M M M M M M F M F M M M M F F F M M F F M F F F M M M M F

48†

Haug et al7‡

1990

35

F

49 50 51 52* 53

Strand-Pettinen16‡ Guest & Juniper22‡ Svensson & Isacsson19‡ Ataoglu et al20‡ Present case‡

1990 1991 1993 1994 1997

20 26 14 23 17

F M M M M

Radiographic Appearance

Margin

⫺ ⫺ ⫺ ⫺ ⫹

NOTE. 8 recent cases‡ are added to the literature, including the current case. * Recurrent benign osteoblastomas. † Multicentric lesions. Modified and reprinted with permission.17

ered as a true neoplasm, some lesions may originate as a result of an individual altered local biologic reaction of bone of unknown origin to trauma or inflammation or from faulty tissue repair. This may explain the presence of some chronic inflammatory cells in this lesion, a histologic finding that was not reported in

the previously documented cases in the maxillofacial region. The biologic behavior of benign osteoblastoma is not constant, and it shows wide variations. Although considered benign, some lesions show aggressive behavior and rare malignant transformation into histo-

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FIGURE 7. Postoperative panoramic radiograph showing complete healing of the involved area with normal bone.

logically typical osteosarcoma.9,21,34,35 It has been reported that one fourth of benign osteoblastoma display radiographic features of a malignant neoplasm.9 However, none of them were located in the jaw bones, and several authors believe that such lesions are, in fact, well-differentiated osteosarcomas resembling osteoblastomas.12,15,36 The histology of an osteoblastoma can indeed mimic that of an osteogenic sarcoma. About 10% of cases of benign osteoblastoma from all sites have been found to show recurrence.37 Only 5 cases of osteoblastoma of the jaws were reported to show recurrence after apparent complete excision of the tumor.10,13,18,20,33 All of the recurrences were located in the mandible, developed within 1 year postoperatively, and were in male patients. Recurrence was attributed to inadequate or conservative initial treatment, including incomplete local curettage or

FIGURE 8. Postoperative anterior view showing complete resolution of the lesion and lack of bony expansion.

partial resection of the tumor,20,21 and not to inherent biologic behavior. However, even with a limited conservative approach, complete resolution or regression have occurred and, in some cases, spontaneous regression took place after biopsy.24,30 When a conservative approach is used, close long-term follow-up of the case is paramount; in the current case, no sign of recurrence was observed 1 year postoperatively. The radiographic appearance of benign osteoblastoma is not diagnostic. Furthermore, the tumor of the jaw bone is not clinically distinctive. Therefore, fibroosseous lesions and tumors of bony origin should be considered in the differential diagnosis.3,6,8,11,13,38,39 The tumor in this case was differentiated from osteoid osteoma, which is histologically characterized by a central nidus of osteoid tissue and a constant perifocal osseous reaction, a scanty stromal reaction, rare multinucleated giant cells, and less vascularization than the benign osteoblastoma.1,11,13,40 In osteoblastoma, most of the hard tissue is imperfectly calcified. Cementoblastoma was excluded because this lesion is found in association with or fused to teeth, and consists of cementum-like tissue. Cementifying fibroma, however, shows a fibrous stroma with a focus of cementoid tissue and no osteoblasts or bone formation.11 Ossifying fibroma is similar clinically and radiographically to osteoblastoma. Both can form immature bone, but the former is painless, more fibrous, and less vascular, and lacks the presence of a large number of plump, actively proliferating, osteoblasts as seen in this case.11,13,40 Fibrous dysplasia is poorly defined radiographically, it shows multilocular radiolucencies in the early stages, and the ground-glass appearance is very characteristic in the more mature stages. It tends to be more ossified in the craniomaxillofacial region.6 In Paget’s disease, the patient’s are older, there is elevation of the serum alkaline phosphatase level, and the lesion is less vascular, and it is characterized histologically by a mosaic pattern of bone formation.

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Although chondroblastoma occurs in young persons, it is relatively rare in the jaw bones and is distinguished by the presence of cartilage cells and a cartilaginous matrix with no significant osteoblastic activity.11 Differentiation of osteoblastoma from lowgrade osteosarcoma can sometimes be extremely difficult.3,9,35,40 Low-grade osteosarcoma was excluded from the differential diagnosis of this tumor because no cellular atypia, pleomorphism, or abnormal mitosis were observed in the tumor cells. Besides, osteosarcoma is an ill-demarcated lesion and histologically shows anaplastic bone formation.1,11,13 The histologic pattern in this case was, therefore, far from that of an osteosarcoma. Odontogenic fibroma and myxoma are tumors of odontogenic mesenchymal origin and therefore can be differentiated from the current tumor because they are located away from the toothbearing area. Odontogenic fibroma is a well-defined lesion characterized histologically by abundant fibroblasts and occasional odontogenic epithelium. Aneurysmal bone cyst and giant cell granuloma were considered in the differential diagnosis of the lesion. Both are well-vascularized lesions with large dilated vascular spaces filled with blood in a connective tissue stroma and are associated with multinucleated giant cells and minimal bone formation at the periphery. Abundant osteoid formation, as seen in this case, is rarely encountered, and the pattern of growth is not as aggressive as with osteoblastoma.1,13,21,34,41

9. Mcleod RA, Dahlin DC, Beabout JW: The spectrum of osteoblastoma. AJR Am J Roentgenol 126:321, 1976 10. Borello ED, Sedano HO: Giant osteoid osteoma of the maxilla. Oral Surg Oral Med Oral Pathol 23:563, 1967 11. Farman AG, Nartje CJ, Grotepass F: Periosteal benign osteoblastoma of the mandible: Report of a case and review of the literature pertaining of benign osteoblastic neoplasms of the jaws. Br J Oral Surg 14:12, 1976 12. Huvos G: Bone Tumors. Diagnosis. Treatment and Prognosis. Philadelphia, PA, Saunders, 1979, p 33 13. Kent JN, Castro MF, Girotti WR: Benign osteoblastoma of the maxilla: Case report and review of the literature. J Oral Surg 27:209, 1969 14. Smith RA, Hansen LS, Resnick D, et al: Comparison of the osteoblastoma in gnathic and extragnathic sites. Oral Surg Oral Med Oral Pathol 54:285, 1982 15. Weinberg S, Katsikeris N, Pharoah M: Osteoblastoma of the mandibular condyle: Review of the literature and report of a case. J Oral Maxillofac Surg 45:350, 1987 16. Strand-Pettinen I, Lukinmaa PL, Holtro ¨m T, et al: Benign osteoblastoma of the mandible. Br J Oral Maxillofac Surg 28:311, 1990 17. Asada Y, Suzuki I, Suzuki M, et al: Atypical multiple benign osteoblastomas accompanied by simple bone cysts. J Craniomaxillofac Surg 19:166, 1991 18. Colm SJ, Abrams MB, Waldron CA: Recurrent osteoblastoma of the mandible: Report of a case. J Oral Maxillofac Surg 46:881, 1988 19. Svensson B, Isacsson G: Benign osteoblastoma associated with an aneurysmal bone cyst of the mandibular ramus and condyle. Oral Surg Oral Med Oral Pathol 16:433, 1993 20. Ataoglu O, Oygur T, Yamalik K, et al: Recurrent osteoblastoma of the mandible: A case report. J Oral Maxillofac Surg 52:86, 1994 21. Ohkubo T, Hernandez JC, Ooya K, et al: Aggressive osteoblastoma of the maxilla. Oral Surg Oral Med Oral Pathol 68:69, 1989 22. Guest PG, Juniper RP: Osteoblastoma: A case report and description of the access used to the retromaxillary area. Br J Oral Maxillofac Surg 29:333, 1991 23. Brady CL, Browne RM: Benign osteoblastoma of mandible. Cancer 30:329, 1972 24. Kramer HS: Benign osteoblastoma of the mandible. Oral Surg Oral Med Oral Pathol 24:842, 1967 25. Remagen W, Prein J: Benign osteoblastoma. Oral Surg 39:279, 1975 26. Wickenhauser J, Strassel H, Hollmann K: Das benign osteoblastoma selten lokalisation in der maxilla? Fort Schr Ro ¨ ntgenst 119:618, 1973 27. Kopp WK: Benign osteoblastoma of the coronoid process of the mandible: Report of a case. J Oral Surg 27:653, 1969 28. Martin NL, Preston DF, Robinson RG: Osteoblastoma of the axial skeleton shown by skeleton scanning: Case report. J Nucl Med 17:187, 1976 29. Ito T, Soga K, Imai T, et al: A case of osteoblastoma of the left coronal process. Jpn J Oral Surg 19:183, 1973 30. Eisenbud L, Kahn LB, Friedmann E: Benign osteoblastoma of the mandible: A fifteen-year follow up showing spontaneous regression after biopsy. J Oral Maxillofac Surg 45:53, 1987 31. Hatakeyama S, Suzuki A: Ultra structural study of benign osteoblastoma of the maxilla. Acta Pathol Jpn 29:791, 1979 32. Sidhuss, Parkash H, Dhanani N: Benign osteoblastoma of the mandible. J Dent 8:254, 1980 33. Smith NHH: Benign osteoblastoma of the mandible: Report of a case. J Oral Surg 30:288, 1972 34. Dorfman HD, Weiss SW: Border line osteoblastic tumors: Problems in the differential diagnosis of aggressive osteoblastoma and low-grade osteosarcoma. Semin Diagn Pathol 1:215, 1984 35. Mirra JM, Kendick RA, Kendick RE: Pseudomalignant osteoblastoma versus arrested osteosarcoma: A case report. Cancer 37: 2005, 1976 36. Bertoni F, Unni KK, Mcleod RA, et al: Osteosarcoma resembling osteoblastoma. Cancer 55:416, 1985 37. Jackson RP: Recurrent osteoblastoma. A review. Clin Orthop 131:229, 1978

Acknowledgment The authors thank Professor H.A. Mosadomi, Director of the Postgraduate Dental Education, College of Dentistry, King Saud University, for his kind help and valuable contribution in review of the histopathology and production of the photomicrographs.

References 1. Lichtenstein L: Benign osteoblastoma, category of osteoid and bone-forming tumors other than classical osteoid osteoma, which may be mistaken for giant-cell tumor or osteogenic sarcoma. Cancer 9:1044, 1956 2. Jaffe HL: Benign osteoblastoma. Bull Hosp Joint Dis 17:141, 1956 3. Makek M: Benign Osteoblastoma: Clinical Pathology of Fibroosseous Cemental Lesions in the Craniofacial and Jaw Bones: A New Approach to Differential Diagnosis. Zurich, Switzerland, Karger, 1983 4. Lichenstein L, Sawyer WR: Benign osteoblastoma: Further observations and report of twenty additional cases. J Bone Joint Surg Am 46:755, 1964 5. Obwegeser HL: Temporal approach of the temporomandibular joint: The orbit and the retromaxillary-intracranial region. J Head Neck Surg 7:185, 1985 6. Huvos AG: Bone Tumors. Diagnosis, Treatment and Prognosis (ed 2). Philadelphia, PA, Saunders, 1991 7. Haug RH, Hauer C, De Camillo AJ, et al: Benign osteoblastoma of the mandible: Report of a case. J Oral Maxillofac Surg 48:743, 1990 8. El Mofty S, Refai H: Benign osteoblastoma of the maxilla. J Oral Maxillofac Surg 47:60, 1989

1317 38. Nyuu H, Inuyama I: Benign osseous and fibro osseous lesions of the cranial and facial bones. Otolaryngol 50:179, 1978 39. Shatz A, Calderon S, Mintz S: Benign osteoblastoma of the mandible. Oral Surg 61:189, 1986

40. Gree RO, Berman DN: Osteoblastoma of the jaws: Current concepts and differential diagnosis. J Oral Surg 36:304, 1978 41. Marsh BW, Bonfiglio M, Brady LP, et al: Benign osteoblastoma: Range of manifestations. J Bone Joint Surg Am 57:1, 1975