A rare, radiographic `sunray' appearance in fibrous dysplasia ... We report a case of a 19-year-old Thai woman who had fibrous dysplasia (FD) with a rare.
Dentomaxillofacial Radiology (2000) 29, 245 ± 248 ã 2000 Macmillan Publishers Ltd. All rights reserved 0250 ± 832X/00 $15.00 www.nature.com/dmfr
CASE REPORT
A rare, radiographic `sunray' appearance in ®brous dysplasia S Prapayasatok*,1, A Iamaroon2, DA Miles3 and T Kumchai4 1
Department of Oral Radiology, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand; 2Department of Odontology and Oral Pathology, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand; 3Department of Oral Health Science, University of Kentucky College of Dentistry, Lexington, Kentucky, USA; 4Department of Oral Surgery, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand
We report a case of a 19-year-old Thai woman who had ®brous dysplasia (FD) with a rare radiographic `sunray' appearance. The sunray appearance could have been due to either an unusual pattern of calci®cation within the lesion or a periosteal reaction. Keywords: bone diseases, developmental; bone neoplasms; mandible; jaw neoplasms Case report A 19-year-old Thai woman came to the Oral Diagnosis Clinic at the Faculty of Dentistry, Chiang Mai University with a chief complaint of swelling of her left cheek. Her medical history was unremarkable. She reported that the swelling had been gradually growing for 2 years but no pain or paresthesia was present. On clinical examination, there was a hard swelling of the left mandible in the premolar-molar area. Both buccal and lingual cortices were markedly expanded. The overlying mucosa showed an impression of the upper teeth and the lower second premolar was lingually displaced (Figure 1). Radiographically, there was a large, diuse, illde®ned osteoblastic area involving lower left premolar-molar area. The lesion had expanded the alveolar crest between the second premolar and the ®rst molar. The second premolar was displaced; however, root resorption was not evident (Figure 2). From the occlusal ®lm, both buccal and lingual cortices were expanded and a sunray appearance, particularly marked on the buccal side, was clearly visible (Figure 3). A postero-anterior skull projection showed no involvement of other craniofacial bones. A likely diagnosis of osteogenic sarcoma was made. A chest X-ray showed no abnormality. Subsequently, a bone biopsy was performed from the ®rst molar area. Microscopical examination of the lesion revealed bone trabeculae with irregular and immature patterns. The
*Correspondence to: S Prapayasatok, Department of Oral Radiology, Faculty of Dentistry, Chiang Mai University, Chiang Mai 50200, Thailand Received 28 September 1999; accepted 10 March 2000
bone marrow spaces were ®lled with active, yet benignlooking, cellular, ®brous connective tissue (Figure 4). Mitotic ®gures or pleomorphism were not observed. Occasionally, new bone formation associated with plump osteoblastic cells was noted. These ®ndings were considered consistent with ®brous dysplasia (FD). Additionally, chemistry serum showed the levels of calcium, phosphorus, and alkaline phosphatase were within normal ranges. The patient declined a bone scan for ®nancial reasons. With the diagnosis con®rmed, a block resection of the lesion including extraction of the displaced teeth was performed. Serial sections of the resected mandible presented characteristic features of FD. The patient was reviewed at 6 months and 14 months and there were no abnormal signs or symptoms. The follow-up radiograph at 14 months showed an absence of the sunray pattern (Figure 5). A long term follow-up was scheduled to be performed annually for at least 5 years. Discussion Fibrous dysplasia is a skeletal disease characterized by the replacement of normal bone with ®brous connective tissue. It can occur in one or several bones, either as monostotic or polyostotic ®brous dysplasia. The monostotic type is 30 times more common than the polyostotic type.1 The term Jae's type is used for the polyostotic FD with skin pigmentation, whereas Albright's disease must exhibit a triad of characteristics: polyostotic FD, hyperpigmentation of the skin and endocrinopathies. To con®rm the diagnosis of FD, historical, clinical, radiographic and histopathological data are essential.2
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Figure 1 Photograph at presentation showing alveolar bone expansion and displacement of the involved teeth. Note the indentation of the alveolus by the opposing maxillary teeth
Figure 2 Part of a panoramic radiograph showing mixed density lesion with ill-de®ned margins in the lower left premolar-molar region. The lesion has expanded the alveolus and displaced the second premolar
Clinically, FD is most commonly found in long bones usually without signs and symptoms until the occurrence of pathological fracture.3 In the jaws, it is more commonly found in maxilla than in mandible. Lesions in other craniofacial bones, such as the zygoma, frontal bone, sphenoid bone, orbital plates, and occipital bone, have been reported. The age range of 96% of the patients is within the ®rst four decades.4 Pronounced swelling, pain and/or tooth displacement are common signs and symptoms of patients with the jaw lesions.5 Radiographic features of FD are extremely variable from cyst-like radiolucencies to dense, osteoblastic lesions. The radiographic appearance depends upon the amount of ®brous tissue that replaces the normal bone and its distribution.2 Radiopacities occur when the ®brous elements have undergone calci®cation, the so-called `ground glass, orange peel or ®ngerprint appearance'.5 Mostly, the outline of the lesion is indistinct and blends with the normal surrounding bone. The cortex is rarely perforated. The teeth are Dentomaxillofacial Radiology
Figure 3 A true occlusal radiograph showing a `sunray' appearance, especially on the buccal aspect. Note the buccal and lingual bone expansion with loss of the cortices
Figure 4 Histologic feature of the biopsy specimen shows numerous immature woven bone trabeculae in a benign-looking ®brous connective tissue stroma. Characteristic Chinese characters of the trabeculae are present. These appearances are consistent with ®brous dysplasia (H&E, 640)
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Figure 5 An occlusal radiograph taken at 14 months follow-up showing absence of the `sunray' pattern
usually displaced and show loss of lamina dura, but seldom have root resorption.4 Microscopically, FD presents with areas of ®brous tissue and variable amounts of newly formed trabecular bone. The formed bone varies in shape, size and is sometimes similar to Chinese characters.2 In this article, we report a case of FD which exhibited an unusual `sunray' appearance which has not been previously reported. In radiographic terms, `sunray' or `sunburst', or sometimes `spicule', are used for periosteal new bone formation in which new bone is formed perpendicular to the cortex resulting in multiple lines like sunrays.6,7 This event could occur when the periosteum is rapidly stripped from the cortex. It is believed that a variety of substances that contact the inner surface of the exposed periosteum can cause new bone formation. These substances include in¯ammatory products from infection,8 blood from trauma,7 granulomatous reactions or neoplasms.9 Although the sunray pattern is highly suggestive of osteosarcoma and chrondrosarcoma, other jaw lesions sometimes show this feature, such as hemangioma, complex odontoma odontogenic myxoma, benign cementoblastoma and multiple myeloma.5 In our case, we were unable to conclude that the `sunray' appearance we saw was a true periosteal reaction or the pattern of calci®cation of the lesion itself. We could ®nd only one case in the literature, reported by Dahlgren et al,10 that mentions bone destruction and layers of periosteal bone deposition in the mandibular ramus. Therefore, if the `sunray' pattern in our case was a true periosteal reaction, it would be the ®rst documented report of this
appearance. The causes that stimulate the periosteal reaction in this case might have been the lesion itself, trauma or infection. Alternatively, if the `sunray' appearance is not a true periosteal reaction, it might re¯ect the pattern of calci®cation. Mirra and Gold6 used polarized light microscope to investigate bone production in FD. They found that a large number of bone spicules demonstrated Sharpey's-like ®bers. Concomitantly, the sunray periosteal reaction occurs when the bone has formed along perpendicular Sharpey's ®bers that attach between the cortex and the stimulated periosteum. These events may explain why FD in our case showed the `sunray' pattern. Many studies have reported the occurrence of malignant transformation of FD.11,12 However, it is more commonly found in the polyostotic than the monostotic type.12,13 Radiotherapy was believed to be a cause of transformation.14 Nevertheless, spontaneous sarcomatous change has also been reported.15 Yabut et al.16 found only 0.4% of 83 cases of FD that underwent malignant change. Most of these occurred during the third or fourth decades, while the diagnosis of FD was made in childhood. These authors recommended that subsequent development of pain or swelling, with radiographic evidence of changes in the morphology of the lesion, should alert the physician to do an adequate biopsy to rule out sarcomatous transformation.16,17 In our case, the radiographic features were highly suggestive of the possibility of malignant transformation. Therefore we consider long term follow-up mandatory. FD must be dierentiated from low-grade osteosarcoma not only because of their similarities in histological examination but also due to dierences in treatment. Mirra and Gold6 suggested that the presence of even one mitosis per ®ve high-power ®elds of the ®brous tissue component in the lesion along with abnormal cell nuclei in adult patients was not normal for FD. These features could be identi®ed in a premalignant cytological dysplasia, an early sarcomatous transformation of FD, and a low-grade fibroblastic osteosarcoma. However, no histological features of malignancy were seen in our case. In conclusion, we report a case of FD showing a radiographic `sunray' appearance. The `sunray' appearance in this case may be a true periosteal reaction that has never been previously reported or it may be due to an uncommon calci®cation pattern within the lesion.
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Acknowledgements We would like to thank our colleagues from Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand; Dr Siree Poonpipatkul and Dr Surasak Youjareonsook, for providing us the clinical details; and to Dr Piranit Kantaputra for help with the photography.
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