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Solitary fibrous tumor of the buccal space resected in combination with coronoidectomy
Vol. 114 No. 1 July 2012
Solitary fibrous tumor of the buccal space resected in combination with coronoidectomy Hiroyuki Yamada, DDS, PhD,a Yoshiki Hamada, DDS, PhD,b Hisako Fujihara, DDS, PhD,c Kaori Fukami, DMD, PhD,d Kenji Mishima, DDS, PhD,e Kazutoshi Nakaoka, DDS, PhD,c Kenichi Kumagai, DDS, PhD,c and Eisaku Imamura, DDSf Tsurumi University, Showa University, and Yokohama General Hospital, Yokohama, Japan
Solitary fibrous tumor (SFT) is an uncommon spindle-cell mesenchymal tumor of probable fibroblastic derivation that most often occurs in the pleura, where it is typically benign. This report describes a case of a large SFT that arose in the buccal space, and includes computerized tomography, magnetic resonance imaging, and positron emission tomography (PET) findings. 18F-Fluorodeoxyglucose (FDG) PET axial imaging showed weak abnormal accumulation of FDG in the left buccal region. The tumor was located behind the posterior wall of the maxilla, adjacent to the medial aspect of the coronoid process and was compressed between the coronoid and maxillary alveolar processes. We resected it with the use of a transoral approach in combination with coronoidectomy. Coronoidectomy was chosen because it facilitated safe removal of the tumor by improving its visibility and providing enough working space to resect it through a transoral approach. (Oral Surg Oral Med Oral Pathol Oral Radiol 2012;114:e9-e14)
Solitary fibrous tumor (SFT) is an uncommon spindlecell mesenchymal tumor of probable fibroblastic derivation.1 SFT most often occurs in the pleura, where it is typically benign. Rarely, SFT is malignant, with pleomorphism, mitotic activity, necrosis, and large size.2 Because SFT of the head and neck region is rare, the behavior of the tumor in this location is not clearly understood. A recent report describing 153 cases of SFT in the head and neck demonstrated that the most frequently involved sites are the buccal mucosa (26.1%), nasal cavity (9.2%), pharyngeal area (7.8%), tongue (7.2%), and orbit (6.5%).3 SFTs with malignant or atypical features were noted in 10 cases (6.5%). Recurrence seems to be rare after complete excision. Characteristic findings on computerized tomography (CT) or magnetic resonance imaging (MRI) of head and neck SFT have rarely been reported.4 Furthermore, there is only 1 published case report of SFT in the head and a
Lecturer, Department of Oral and Maxillofacial Surgery, School of Dental Medicine, Tsurumi University. b Professor and Chairman, Department of Oral and Maxillofacial Surgery, School of Dental Medicine, Tsurumi University. c Assistant Professor, Department of Oral and Maxillofacial Surgery, School of Dental Medicine, Tsurumi University. d Assistant Professor, Department of Oral and Maxillofacial Radiology and Diagnosis, School of Dental Medicine, Tsurumi University. e Professor, Department of Oral Pathology and Diagnosis, School of Dentistry, Showa University. f Director, Department of Oral and Maxillofacial Surgery, Yokohama General Hospital. Received for publication Jul 13, 2011; returned for revision Jul 22, 2011; accepted for publication Jul 29, 2011. © 2012 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.tripleo.2011.07.044
neck region with positron emission tomography (PET) findings.5 Because of the lack of knowledge regarding findings specific to SFT on CT, MRI, and PET, preoperative diagnosis by imaging of this tumor has been difficult. Small tumors in the buccal space are usually resected via a transoral approach. However, it is difficult to resect a large tumor in the buccal space through the oral cavity, because this approach does not provide an optimal view of the surgical field. In such instances, transcutaneous approaches have been selected.6 We resected a large SFT of the buccal space safely via the oral cavity by incorporating coronoidectomy into the procedure. The coronoidectomy improved visualization of the tumor in the buccal space, and provided enough working space to remove the tumor via a transoral approach; however, this technical indication for coronoidectomy has not been clearly documented in published reports. For these reasons, we report herein a case of SFT in the buccal space with CT, MRI, and PET findings and discuss the technical advantages of coronoidectomy during resection of such a tumor via the transoral approach.
CASE REPORT A 35-year-old woman was referred to the Department of Oral and Maxillofacial Surgery, Tsurumi University Dental Hospital, on December 8, 2009, for diagnosis and treatment of a painless left buccal nodule. She had noted the nodule for approximately 6 months. Her medical and family histories were unremarkable. There was no experience of traumatic injury. Physical examination revealed a rubbery mobile mass measuring 35 ⫻ 20 mm in the left buccal region. The over lying skin and oral mucosa were normal. No bruit or pulsation
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Figure. 1. A, Plain CT scan image reveals displacement of the posterior wall of the maxillary sinus. B, Contrast-enhanced CT scan image reveals a fairly well defined mass measuring 20 ⫻ 40 mm in the left buccal space. The mass is clearly and heterogeneously enhanced.
Figure. 2. Gadolinium-enhanced T1-weighted image showing a homogeneously and highly enhanced mass. was present over the mass. Salivary secretion by the left parotid gland was not disturbed. There was neither neuroparalysis nor cervical lymphadenopathy. A panoramic radiograph revealed that her dentition was in good condition. A helical CT scan was carried out with Radix Prima (Hitachi Medico, Tokyo, Japan). During the CT scan, maximal mouth opening was maintained by using a bite block. CT images showed a well defined mass measuring 20 ⫻ 40 ⫻ 35 mm in the left buccal space bordering on the masseter muscle, posterior wall of the left maxillary sinus, and maxillary alveolar process. The mass was displacing the posterior wall of the maxillary sinus (Figure 1, A), and bone resorption of the maxillary alveolar process was apparent. On the contrastenhanced CT images, the mass was clearly and heterogeneously enhanced (Figure 1, B).
Figure. 3. FDG-PET axial image showing weak abnormal accumulation of FDG in the left buccal region (arrowhead).
MRI was performed with a 1.5-Tesla Intera system (Philips, Eindhoven, The Netherlands). On axial T1-weighted images, the mass showed isosignal intensity with a fairly well defined margin. On T2-weighted images, nonhomogeneous slightly increased signal intensity with hypointense areas was noted within the mass. On gadolinium-enhanced axial T1weighted images, the mass was almost homogeneously strongly enhanced and showed a lobulated configuration with hyposignal structures suggestive of a capsule (Figure 2). A PET study was performed with a Siemens Ecat Accel (Munich, Germany). Data were acquired after administration of 150.7 MBq 18F-fluorodeoxyglucose (FDG), using the postinjection transmission acquisition method. The image showed abnormal weak accumulation of FDG in the left buccal space corresponding to the mass (Figure 3).
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Figure. 4. The left coronoid process and tumor presented as a 3-dimensional CT image. The tumor is shown as an orange-colored mass. The coronoid process was amputated along the blue line. A biopsy was performed via the oral mucosa under local anesthesia, and a yellow-colored tissue specimen was obtained. A fibrous capsule was present around the tumor. The histopathologic diagnosis was benign fibrous histiocytoma (BFH). The tumor was located behind the posterior wall of the maxilla, adjacent to the medial aspect of the coronoid process and compressed between the coronoid and maxillary alveolar processes (Figure 4). To get an optimal view of the surgical field, particularly considering the risks of incomplete resection of the tumor and uncontrollable hemorrhage from the pterygoid venous plexus, coronoidectomy was performed before resection of the tumor. The operation was commenced under general anesthesia after preparing for a transcutaneous approach in case the tumor could not be resected by a transoral approach. Firstly, coronoidectomy was performed. An intraoral incision was made and then the periosteum and tendon of the temporal muscle were released from the coronoid process. After the coronoid process had been amputated, the lateral part of the tumor was directly visible (Figure 5). Next, the incision was extended to the maxillary gingiva and the tumor detached from the surrounding soft tissue. Because the coronoid process had already been removed, there was room to shift the tumor laterally by releasing the periosteum from the maxillary alveolar bone. The tumor mass was soft and elastic and it was relatively easy to separate from the surrounding soft tissue. The postoperative course was uneventful. The patient was free from tumor at a follow-up examination 1 year after surgery. Neither trismus nor occlusal dysfunction developed. Examination of hematoxylin and eosin (HE)–stained sections revealed that the tumor was encapsulated by fibrous connective tissue. Tumor nests were irregularly divided by connective tissue, forming a lobular architecture. Each tumor nest contained both hypercellular and hypocellular areas. The hypercellular areas were composed of spindle cells without
Figure. 5. Photograph showing the intraoperative surgical field after coronoidectomy. The lateral aspect of the tumor is directly visible in the absence of the coronoid process (arrowhead).
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Figure. 6. A, Photomicrograph showing hypercellular and hypocellular areas. Fibroblastic spindle cells have proliferated in an amorphous fashion. The hypocellular areas present prominent myxoid changes (hematoxylin-eosin [HE] stain, original magnification ⫻200). B, Photomicrograph showing hypercellular areas composed of spindle cells without atypia or pleomorphism. The fibroblastic spindle cells have proliferated forming dense collagen fibers (HE stain, original magnification ⫻400). C, Photomicrograph showing cytoplasmic positive immunoreactivity for CD34 (original magnification ⫻400). D, Photomicrograph showing cytoplasmic positive immunoreactivity for Bcl-2 (original magnification ⫻400).
atypia or pleomorphism. Fibroblastic spindle cells had proliferated in an amorphous fashion forming dense collagen fibers. The hypocellular areas presented prominent myxoid changes. In the stroma, numerous thin-walled vessels were observed (Figure 6, A and B). Immunohistochemical staining was carried out by the avidin-biotin method. The spindle tumor cells showed positive immunoreactivity for CD34 (mouse anti– human CD34, monoclonal antibody, clone NU-4A1; Nichirei, Tokyo, Japan; Figure 6, C), and Bcl-2 (mouse anti– human Bcl-2 oncoprotein, clone 124; Dako, Glostrup, Denmark; Figure 6, D). Conversely, the tumor cells were negative for ␣-smooth muscle actin (␣-SMA; mouse anti– human ␣-smooth muscle actin, monoclonal antibody, clone 1A4; Dako-Cytomation, Glostrup, Denmark) and S-100 protein (rabbit anti– human S-100 polyclonal antibody, clone MOC32; Nichirei). All of above the features are diagnostic of solitary fibrous tumor.
DISCUSSION We have described resection of a large SFT in the buccal space via the oral cavity in combination with coronoidectomy. Coronoidectomy is usually performed to treat trismus after oral cancer surgery,7 hyperplasia of coronoid process,8 or masticatory muscle tendonaponeurosis hyperplasia.9 Currently, coronoidectomy is not widely accepted as an essential procedure when resecting a tumor in the buccal space by a transoral approach. Because the space between the maxillary alveolar process and coronoid process of the mandible is narrow, tumors positioned behind the posterior wall of the maxilla can not easily be pulled out through this space. Where a tumor in the buccal space is small or very soft, coronoidectomy would not always be necessary; however, where a tumor is large and hard, coro-
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noidectomy would make it much easier to remove the tumor safely using a transoral approach. Coronoidectomy provides enough surgical space to work with surgical instruments and to detach the surrounding soft tissue to remove the tumor. One disadvantage of coronoidectomy is that it sacrifices normal tissue. In addition, because the temporal muscle stabilizes the mandible, occlusal dysfunction may occur after coronoidectomy. However, the complication of occlusal function has not been described after coronoidectomy performed to treat trismus.7,9 The temporal muscle originates from the temporal bone and inserts into the coronoid process and mandibular ramus. Therefore, the function of the deeper part of temporal muscle, which inserts into the mandibular ramus, would be preserved after coronoidectomy. In the present case, neither postoperative trismus nor occlusal dysfunction developed. Coronoidectomy is an option that should be considered when planning surgery to remove a large tumor in the buccal space safely by a transoral approach. In fact, the application of coronoidectomy in our patient allowed us to avoid a transcutaneous approach, resulting in a good cosmetic result. Preoperative CT performed with the patient’s mouth held open to the maximum allowed us to evaluate the relationships between the coronoid process, maxillary alveolar process, and tumor. CT of SFTs in the head and neck has been reported to show soft-tissue masses with heterogeneous enhancement by contrast material.10,11 MRI of these SFTs demonstrates iso signal intensity on T1-weighted images with strong enhancement by contrast material in the tumors. On T2-weighted images, the tumors appear as heterogeneous masses with hypo- and hypersignal intensity.10,12 In the present case, CT and MRI findings were consistent with those of reported cases.10,12 Regarding FDG-PET findings of SFT arising in the head and neck, only 1 earlier case report has been published in English. In that case, heterogeneous mild uptake of FDG in an SFT of the parapharyngeal space was documented.5 In the present case, abnormal weak FDG accumulation in the SFT in the buccal space was observed. FDG accumulation in tumor occurs in 2 steps. High signals of FDG-PET are caused mainly by FDG being brought to the region via the bloodstream and then undergoing metabolic trapping by the cells.13 For glucose to be taken up and used by tumor cells, an adequate blood supply is needed. SFTs are known to be richly vascularized tumors,14 their angiogenic nature having been demonstrated by ultrastructural analysis.15 Also, in the present case, a rich blood flow to the SFT was demonstrated by contrast-enhanced CT and MRI findings. Moreover, many blood vessels were ob-
CASE REPORT Yamada et al. e13
served histopathologically on HE-stained sections of the SFT. In the present case, the histopathologic diagnosis of the biopsy specimen was BFH. Diagnosis of SFT in a small biopsy specimen is known to be difficult, because of extreme intratumor variability and the close similarity of isolated parts of individual soft tissue tumors.16 The differential diagnosis of spindle cell tumor includes leiomyoma, BFH, myofibroma, and schwannoma. In addition to typical histopathologic findings in HEstained sections, negative findings for ␣-SMA and S100 protein have been proved to exclude leiomyoma, BFH, myofibroma, and schwannoma. Moreover, positive findings of CD34 and Bcl-2 are highly supportive of the diagnosis of SFT.17,18 In conclusion, coronoidectomy can facilitate the excision of large tumors in the buccal space via a transoral approach. We have also documented the PET findings of weak FDG accumulation in an SFT in the head and neck region. REFERENCES 1. Travis WD, Churg A, Aubry MC, Ordonez NG, Tazelaar H, Pugatch R, et al. Mesenchymal tumours. In: Travis WD, Brambilla E, Müller-Hermelink HK, Harris CC, editors. Pathology and genetics of tumours of the lung, pleura, thymus and heart. Lyon: International Agency for Research on Cancer (IARC); 2004. p. 141-4. 2. Husain AN. The lung. In: Kumar V, Abbas AK, Fausto N, Aster JC, editors. Robbins and Cotran pathologic basis of disease. 8th ed. Philadelphia: Elsevier Saunders; 2009. p. 732-3. 3. Cox DP, Daniels T, Jordan RC. Solitary fibrous tumor of the head and neck. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;110:79-84. 4. Kim HJ, Lee HK, Seo JJ, Kim HJ, Shin JH, Jeong AK, et al. MR imaging of solitary fibrous tumors in the head and neck. Korean J Radiol 2005;6:136-42. 5. Wakisaka N, Kondo S, Murono S, Minato H, Furukawa M, Yoshizaki T. A solitary fibrous tumor arising in the parapharyngeal space, with MRI and FDG-PET findings. Auris Nasus Larynx 2009;36:367-71. 6. Gallia L, Rood SR, Myers EN. Management of buccal space masses. Otolaryngol Head Neck Surg 1981;89:221-5. 7. Celik N, Wei FC, Chang YM, Yang WG, Chen DJ, Tsai CY. Squamous cell carcinoma of the oral mucosa after release of submucous fibrosis and bilateral small radial forearm flap reconstruction. Plast Reconstr Surg 2002;110:34-8. 8. McLoughlin PM, Hopper C, Bowley NB. Hyperplasia of the mandibular coronoid process: an analysis of 31 cases and a review of the literature. J Oral Maxillofac Surg 1995;53:250-5. 9. Yoda T, Sato T, Abe T, Sakamoto I, Tomaru Y, Omura K, et al. Long-term results of surgical therapy for masticatory muscle tendon-aponeurosis hyperplasia accompanied by limited mouth opening. Int J Oral Maxillofac Surg 2009;38:1143-7. 10. Schirmang TC, Davis LM, Nigri PT, Dupuy DE. Solitary fibrous tumor of the buccal space: treatment with percutaneous cryoablation. AJNR Am J Neuroradiol 2007;28:1728-30. 11. Morales-Cadena M, Zubiaur FM, Alvarez R, Madrigal J, ZarateOsorno A. Solitary fibrous tumor of the nasal cavity and paranasal sinuses. Otolaryngol Head Neck Surg 2006;135:980-2. 12. Dunfee BL, Sakai O, Spiegel JH, Pistey R. Solitary fibrous tumor of the buccal space. AJNR Am J Neuroradiol 2005;26:2114-6.
ORAL AND MAXILLOFACIAL SURGERY e14 Yamada et al. 13. Gallagher BM, Fowler JS, Gutterson NI, MacGregor RR, Wan CN, Wolf AP. Metabolic trapping as a principle of oradiopharmaceutical design: some factors resposible for the biodistribution of [18F]2deoxy-2-fluoro-d-glucose. J Nucl Med 1978;19:1154-61. 14. Galioto S, Valentini V, Fatone FM, Rabagliati M, Autelitano L, Iannetti G. Solitary fibrous tumours of the infratemporal fossa. Two case reports. J Craniomaxillofac Surg 2006;34:494-501. 15. Ide F, Obara K, Mishima K, Saito I, Kusama K. Ultrastructural spectrum of solitary fibrous tumor: a unique perivascular tumor with alternative lines of differentiation. Virchows Arch 2005;446:646-52. 16. Lo Muzio L, Mascolo M, Capodiferro S, Favia G, Maiorano E. Solitary fibrous tumor of the oral cavity: the need for an extensive sampling for a correct diagnosis. J Oral Pathol Med 2007;36:538-42. 17. Alawi F, Stratton D, Freedman PD. Solitary fibrous tumor of the oral soft tissues: a clinicopathologic and immunohistochemical study of 16 cases. Am J Surg Pathol 2001;25:900-10.
OOOO July 2012 18. O’Regan EM, Vanguri V, Allen CM, Eversole LR, Wright JM, Woo SB. Solitary fibrous tumor of the oral cavity: clinicopathologic and immunohistochemical study of 21 cases. Head Neck. Pathologe 2009;3:106-15.
Reprint requests: Dr. H. Yamada Department of Oral and Maxillofacial Surgery School of Dental Medicine Tsurumi University 2-1-3 Tsurumi Yokohama, 230-8501 Japan [email protected]
Solitary fibrous tumor of the buccal space resected in combination with coronoidectomy Hiroyuki Yamada, DDS, PhD,a Yoshiki Hamada, DDS, PhD,b Hisako Fujihara, DDS, PhD,c Kaori Fukami, DMD, PhD,d Kenji Mishima, DDS, PhD,e Kazutoshi Nakaoka, DDS, PhD,c Kenichi Kumagai, DDS, PhD,c and Eisaku Imamura, DDSf Tsurumi University, Showa University, and Yokohama General Hospital, Yokohama, Japan
Solitary fibrous tumor (SFT) is an uncommon spindle-cell mesenchymal tumor of probable fibroblastic derivation that most often occurs in the pleura, where it is typically benign. This report describes a case of a large SFT that arose in the buccal space, and includes computerized tomography, magnetic resonance imaging, and positron emission tomography (PET) findings. 18F-Fluorodeoxyglucose (FDG) PET axial imaging showed weak abnormal accumulation of FDG in the left buccal region. The tumor was located behind the posterior wall of the maxilla, adjacent to the medial aspect of the coronoid process and was compressed between the coronoid and maxillary alveolar processes. We resected it with the use of a transoral approach in combination with coronoidectomy. Coronoidectomy was chosen because it facilitated safe removal of the tumor by improving its visibility and providing enough working space to resect it through a transoral approach. (Oral Surg Oral Med Oral Pathol Oral Radiol 2012;114:e9-e14)
Solitary fibrous tumor (SFT) is an uncommon spindlecell mesenchymal tumor of probable fibroblastic derivation.1 SFT most often occurs in the pleura, where it is typically benign. Rarely, SFT is malignant, with pleomorphism, mitotic activity, necrosis, and large size.2 Because SFT of the head and neck region is rare, the behavior of the tumor in this location is not clearly understood. A recent report describing 153 cases of SFT in the head and neck demonstrated that the most frequently involved sites are the buccal mucosa (26.1%), nasal cavity (9.2%), pharyngeal area (7.8%), tongue (7.2%), and orbit (6.5%).3 SFTs with malignant or atypical features were noted in 10 cases (6.5%). Recurrence seems to be rare after complete excision. Characteristic findings on computerized tomography (CT) or magnetic resonance imaging (MRI) of head and neck SFT have rarely been reported.4 Furthermore, there is only 1 published case report of SFT in the head and a
Lecturer, Department of Oral and Maxillofacial Surgery, School of Dental Medicine, Tsurumi University. b Professor and Chairman, Department of Oral and Maxillofacial Surgery, School of Dental Medicine, Tsurumi University. c Assistant Professor, Department of Oral and Maxillofacial Surgery, School of Dental Medicine, Tsurumi University. d Assistant Professor, Department of Oral and Maxillofacial Radiology and Diagnosis, School of Dental Medicine, Tsurumi University. e Professor, Department of Oral Pathology and Diagnosis, School of Dentistry, Showa University. f Director, Department of Oral and Maxillofacial Surgery, Yokohama General Hospital. Received for publication Jul 13, 2011; returned for revision Jul 22, 2011; accepted for publication Jul 29, 2011. © 2012 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.tripleo.2011.07.044
neck region with positron emission tomography (PET) findings.5 Because of the lack of knowledge regarding findings specific to SFT on CT, MRI, and PET, preoperative diagnosis by imaging of this tumor has been difficult. Small tumors in the buccal space are usually resected via a transoral approach. However, it is difficult to resect a large tumor in the buccal space through the oral cavity, because this approach does not provide an optimal view of the surgical field. In such instances, transcutaneous approaches have been selected.6 We resected a large SFT of the buccal space safely via the oral cavity by incorporating coronoidectomy into the procedure. The coronoidectomy improved visualization of the tumor in the buccal space, and provided enough working space to remove the tumor via a transoral approach; however, this technical indication for coronoidectomy has not been clearly documented in published reports. For these reasons, we report herein a case of SFT in the buccal space with CT, MRI, and PET findings and discuss the technical advantages of coronoidectomy during resection of such a tumor via the transoral approach.
CASE REPORT A 35-year-old woman was referred to the Department of Oral and Maxillofacial Surgery, Tsurumi University Dental Hospital, on December 8, 2009, for diagnosis and treatment of a painless left buccal nodule. She had noted the nodule for approximately 6 months. Her medical and family histories were unremarkable. There was no experience of traumatic injury. Physical examination revealed a rubbery mobile mass measuring 35 ⫻ 20 mm in the left buccal region. The over lying skin and oral mucosa were normal. No bruit or pulsation
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Figure. 1. A, Plain CT scan image reveals displacement of the posterior wall of the maxillary sinus. B, Contrast-enhanced CT scan image reveals a fairly well defined mass measuring 20 ⫻ 40 mm in the left buccal space. The mass is clearly and heterogeneously enhanced.
Figure. 2. Gadolinium-enhanced T1-weighted image showing a homogeneously and highly enhanced mass. was present over the mass. Salivary secretion by the left parotid gland was not disturbed. There was neither neuroparalysis nor cervical lymphadenopathy. A panoramic radiograph revealed that her dentition was in good condition. A helical CT scan was carried out with Radix Prima (Hitachi Medico, Tokyo, Japan). During the CT scan, maximal mouth opening was maintained by using a bite block. CT images showed a well defined mass measuring 20 ⫻ 40 ⫻ 35 mm in the left buccal space bordering on the masseter muscle, posterior wall of the left maxillary sinus, and maxillary alveolar process. The mass was displacing the posterior wall of the maxillary sinus (Figure 1, A), and bone resorption of the maxillary alveolar process was apparent. On the contrastenhanced CT images, the mass was clearly and heterogeneously enhanced (Figure 1, B).
Figure. 3. FDG-PET axial image showing weak abnormal accumulation of FDG in the left buccal region (arrowhead).
MRI was performed with a 1.5-Tesla Intera system (Philips, Eindhoven, The Netherlands). On axial T1-weighted images, the mass showed isosignal intensity with a fairly well defined margin. On T2-weighted images, nonhomogeneous slightly increased signal intensity with hypointense areas was noted within the mass. On gadolinium-enhanced axial T1weighted images, the mass was almost homogeneously strongly enhanced and showed a lobulated configuration with hyposignal structures suggestive of a capsule (Figure 2). A PET study was performed with a Siemens Ecat Accel (Munich, Germany). Data were acquired after administration of 150.7 MBq 18F-fluorodeoxyglucose (FDG), using the postinjection transmission acquisition method. The image showed abnormal weak accumulation of FDG in the left buccal space corresponding to the mass (Figure 3).
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CASE REPORT Yamada et al. e11
Figure. 4. The left coronoid process and tumor presented as a 3-dimensional CT image. The tumor is shown as an orange-colored mass. The coronoid process was amputated along the blue line. A biopsy was performed via the oral mucosa under local anesthesia, and a yellow-colored tissue specimen was obtained. A fibrous capsule was present around the tumor. The histopathologic diagnosis was benign fibrous histiocytoma (BFH). The tumor was located behind the posterior wall of the maxilla, adjacent to the medial aspect of the coronoid process and compressed between the coronoid and maxillary alveolar processes (Figure 4). To get an optimal view of the surgical field, particularly considering the risks of incomplete resection of the tumor and uncontrollable hemorrhage from the pterygoid venous plexus, coronoidectomy was performed before resection of the tumor. The operation was commenced under general anesthesia after preparing for a transcutaneous approach in case the tumor could not be resected by a transoral approach. Firstly, coronoidectomy was performed. An intraoral incision was made and then the periosteum and tendon of the temporal muscle were released from the coronoid process. After the coronoid process had been amputated, the lateral part of the tumor was directly visible (Figure 5). Next, the incision was extended to the maxillary gingiva and the tumor detached from the surrounding soft tissue. Because the coronoid process had already been removed, there was room to shift the tumor laterally by releasing the periosteum from the maxillary alveolar bone. The tumor mass was soft and elastic and it was relatively easy to separate from the surrounding soft tissue. The postoperative course was uneventful. The patient was free from tumor at a follow-up examination 1 year after surgery. Neither trismus nor occlusal dysfunction developed. Examination of hematoxylin and eosin (HE)–stained sections revealed that the tumor was encapsulated by fibrous connective tissue. Tumor nests were irregularly divided by connective tissue, forming a lobular architecture. Each tumor nest contained both hypercellular and hypocellular areas. The hypercellular areas were composed of spindle cells without
Figure. 5. Photograph showing the intraoperative surgical field after coronoidectomy. The lateral aspect of the tumor is directly visible in the absence of the coronoid process (arrowhead).
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Figure. 6. A, Photomicrograph showing hypercellular and hypocellular areas. Fibroblastic spindle cells have proliferated in an amorphous fashion. The hypocellular areas present prominent myxoid changes (hematoxylin-eosin [HE] stain, original magnification ⫻200). B, Photomicrograph showing hypercellular areas composed of spindle cells without atypia or pleomorphism. The fibroblastic spindle cells have proliferated forming dense collagen fibers (HE stain, original magnification ⫻400). C, Photomicrograph showing cytoplasmic positive immunoreactivity for CD34 (original magnification ⫻400). D, Photomicrograph showing cytoplasmic positive immunoreactivity for Bcl-2 (original magnification ⫻400).
atypia or pleomorphism. Fibroblastic spindle cells had proliferated in an amorphous fashion forming dense collagen fibers. The hypocellular areas presented prominent myxoid changes. In the stroma, numerous thin-walled vessels were observed (Figure 6, A and B). Immunohistochemical staining was carried out by the avidin-biotin method. The spindle tumor cells showed positive immunoreactivity for CD34 (mouse anti– human CD34, monoclonal antibody, clone NU-4A1; Nichirei, Tokyo, Japan; Figure 6, C), and Bcl-2 (mouse anti– human Bcl-2 oncoprotein, clone 124; Dako, Glostrup, Denmark; Figure 6, D). Conversely, the tumor cells were negative for ␣-smooth muscle actin (␣-SMA; mouse anti– human ␣-smooth muscle actin, monoclonal antibody, clone 1A4; Dako-Cytomation, Glostrup, Denmark) and S-100 protein (rabbit anti– human S-100 polyclonal antibody, clone MOC32; Nichirei). All of above the features are diagnostic of solitary fibrous tumor.
DISCUSSION We have described resection of a large SFT in the buccal space via the oral cavity in combination with coronoidectomy. Coronoidectomy is usually performed to treat trismus after oral cancer surgery,7 hyperplasia of coronoid process,8 or masticatory muscle tendonaponeurosis hyperplasia.9 Currently, coronoidectomy is not widely accepted as an essential procedure when resecting a tumor in the buccal space by a transoral approach. Because the space between the maxillary alveolar process and coronoid process of the mandible is narrow, tumors positioned behind the posterior wall of the maxilla can not easily be pulled out through this space. Where a tumor in the buccal space is small or very soft, coronoidectomy would not always be necessary; however, where a tumor is large and hard, coro-
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noidectomy would make it much easier to remove the tumor safely using a transoral approach. Coronoidectomy provides enough surgical space to work with surgical instruments and to detach the surrounding soft tissue to remove the tumor. One disadvantage of coronoidectomy is that it sacrifices normal tissue. In addition, because the temporal muscle stabilizes the mandible, occlusal dysfunction may occur after coronoidectomy. However, the complication of occlusal function has not been described after coronoidectomy performed to treat trismus.7,9 The temporal muscle originates from the temporal bone and inserts into the coronoid process and mandibular ramus. Therefore, the function of the deeper part of temporal muscle, which inserts into the mandibular ramus, would be preserved after coronoidectomy. In the present case, neither postoperative trismus nor occlusal dysfunction developed. Coronoidectomy is an option that should be considered when planning surgery to remove a large tumor in the buccal space safely by a transoral approach. In fact, the application of coronoidectomy in our patient allowed us to avoid a transcutaneous approach, resulting in a good cosmetic result. Preoperative CT performed with the patient’s mouth held open to the maximum allowed us to evaluate the relationships between the coronoid process, maxillary alveolar process, and tumor. CT of SFTs in the head and neck has been reported to show soft-tissue masses with heterogeneous enhancement by contrast material.10,11 MRI of these SFTs demonstrates iso signal intensity on T1-weighted images with strong enhancement by contrast material in the tumors. On T2-weighted images, the tumors appear as heterogeneous masses with hypo- and hypersignal intensity.10,12 In the present case, CT and MRI findings were consistent with those of reported cases.10,12 Regarding FDG-PET findings of SFT arising in the head and neck, only 1 earlier case report has been published in English. In that case, heterogeneous mild uptake of FDG in an SFT of the parapharyngeal space was documented.5 In the present case, abnormal weak FDG accumulation in the SFT in the buccal space was observed. FDG accumulation in tumor occurs in 2 steps. High signals of FDG-PET are caused mainly by FDG being brought to the region via the bloodstream and then undergoing metabolic trapping by the cells.13 For glucose to be taken up and used by tumor cells, an adequate blood supply is needed. SFTs are known to be richly vascularized tumors,14 their angiogenic nature having been demonstrated by ultrastructural analysis.15 Also, in the present case, a rich blood flow to the SFT was demonstrated by contrast-enhanced CT and MRI findings. Moreover, many blood vessels were ob-
CASE REPORT Yamada et al. e13
served histopathologically on HE-stained sections of the SFT. In the present case, the histopathologic diagnosis of the biopsy specimen was BFH. Diagnosis of SFT in a small biopsy specimen is known to be difficult, because of extreme intratumor variability and the close similarity of isolated parts of individual soft tissue tumors.16 The differential diagnosis of spindle cell tumor includes leiomyoma, BFH, myofibroma, and schwannoma. In addition to typical histopathologic findings in HEstained sections, negative findings for ␣-SMA and S100 protein have been proved to exclude leiomyoma, BFH, myofibroma, and schwannoma. Moreover, positive findings of CD34 and Bcl-2 are highly supportive of the diagnosis of SFT.17,18 In conclusion, coronoidectomy can facilitate the excision of large tumors in the buccal space via a transoral approach. We have also documented the PET findings of weak FDG accumulation in an SFT in the head and neck region. REFERENCES 1. Travis WD, Churg A, Aubry MC, Ordonez NG, Tazelaar H, Pugatch R, et al. Mesenchymal tumours. In: Travis WD, Brambilla E, Müller-Hermelink HK, Harris CC, editors. Pathology and genetics of tumours of the lung, pleura, thymus and heart. Lyon: International Agency for Research on Cancer (IARC); 2004. p. 141-4. 2. Husain AN. The lung. In: Kumar V, Abbas AK, Fausto N, Aster JC, editors. Robbins and Cotran pathologic basis of disease. 8th ed. Philadelphia: Elsevier Saunders; 2009. p. 732-3. 3. Cox DP, Daniels T, Jordan RC. Solitary fibrous tumor of the head and neck. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;110:79-84. 4. Kim HJ, Lee HK, Seo JJ, Kim HJ, Shin JH, Jeong AK, et al. MR imaging of solitary fibrous tumors in the head and neck. Korean J Radiol 2005;6:136-42. 5. Wakisaka N, Kondo S, Murono S, Minato H, Furukawa M, Yoshizaki T. A solitary fibrous tumor arising in the parapharyngeal space, with MRI and FDG-PET findings. Auris Nasus Larynx 2009;36:367-71. 6. Gallia L, Rood SR, Myers EN. Management of buccal space masses. Otolaryngol Head Neck Surg 1981;89:221-5. 7. Celik N, Wei FC, Chang YM, Yang WG, Chen DJ, Tsai CY. Squamous cell carcinoma of the oral mucosa after release of submucous fibrosis and bilateral small radial forearm flap reconstruction. Plast Reconstr Surg 2002;110:34-8. 8. McLoughlin PM, Hopper C, Bowley NB. Hyperplasia of the mandibular coronoid process: an analysis of 31 cases and a review of the literature. J Oral Maxillofac Surg 1995;53:250-5. 9. Yoda T, Sato T, Abe T, Sakamoto I, Tomaru Y, Omura K, et al. Long-term results of surgical therapy for masticatory muscle tendon-aponeurosis hyperplasia accompanied by limited mouth opening. Int J Oral Maxillofac Surg 2009;38:1143-7. 10. Schirmang TC, Davis LM, Nigri PT, Dupuy DE. Solitary fibrous tumor of the buccal space: treatment with percutaneous cryoablation. AJNR Am J Neuroradiol 2007;28:1728-30. 11. Morales-Cadena M, Zubiaur FM, Alvarez R, Madrigal J, ZarateOsorno A. Solitary fibrous tumor of the nasal cavity and paranasal sinuses. Otolaryngol Head Neck Surg 2006;135:980-2. 12. Dunfee BL, Sakai O, Spiegel JH, Pistey R. Solitary fibrous tumor of the buccal space. AJNR Am J Neuroradiol 2005;26:2114-6.
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Reprint requests: Dr. H. Yamada Department of Oral and Maxillofacial Surgery School of Dental Medicine Tsurumi University 2-1-3 Tsurumi Yokohama, 230-8501 Japan [email protected]