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ISSN : 1225-1577(Print)
ISSN : 2384-0900(Online)
The Korean Journal of Oral and Maxillofacial Pathology Vol.43 No.4 pp.115-120
DOI : https://doi.org/10.17779/KAOMP.2019.43.4.003

Multilocular Squamous Odontogenic Tumor of Right Maxilla: A Case Report and Literature Review

Won-Bum Lee1), Uk-Kyu Kim2), Hae-Ryoun Park1), Mi-Heon Ryu3), Yun-Hoa Jung4), Jae-Joon Hwang4), Dae-Seok Hwang2)*
1)Dept. of Oral and Maxillofacial Surgery, School of Dentistry, Pusan National University
2)Dept. of Oral and Maxillofacial Surgery, School of Dentistry, Pusan National University, Pusan Dental Hospital
3)Dept. of Oral Pathology, BK21 Plus project, School of Dentistry, Pusan National University
4)Dept. of Oral and Maxillofacial Radiology, School of Dentistry, Pusan National University
Correspondence: Dae-Seok Hwang, Dept. of Oral and Maxillofacial Surgery, Pusan National University Dental Hospital, 20, Geumo-ro, Mulgeum-eup, Yangsan-si, Gyeongsangnam-do, Republic of Korea Tel: +82-55-360-5104, Fax: +82-55-360-5110 E-mail: dshwang@pusan.ac.kr
July 23, 2019 August 2, 2019 August 2, 2019

Abstract


Squamous odontogenic tumor (SOT) is a relatively rare, benign, small (rarely > 1.5 cm in diameter), but locally infiltrative and occasionally aggressive odontogenic epithelial lesion that appears to have harmatomous and neoplastic characteristics [1]. SOT is often asymptomatic, although it can present with mildly painful gingival swelling or tooth mobility. Radiographically, SOT is usually visualized as an irregularly or triangularly shaped unilocular radiolucency associated with the lateral roots of teeth. We report a case of the squamous odontogenic tumor occurring in a 60-year-old female in the right posterior maxilla with unusual radiographic and clinical appearances.


Squamous odontogenic tumor , Maxilla , Radiolucency

우측 상악골에 발생한 다방성 편평 치성 종양 : 치험례 및 문헌고찰

이 원범1), 김 욱규2), 박 혜련1), 유 미현3), 정 연화4), 황 재준4), 황 대석2)*
1)부산대학교 치의학전문대학원 구강악안면외과학 교실
2)부산대학교 치의학전문대학원 구강악안면외과학 교실, 부산대학교치과병원 구강악안면외과
3)부산대학교 치의학전문대학원 구강병리학 교실, BK21 플러스 사업단
4)부산대학교 치의학전문대학원 영상치의학과 교실

초록

    Ⅰ. INTRODUCTION

    Squamous odontogenic tumor (SOT) is rare, benign, odontogenic neoplasm that consists of islands of welldifferentiated squamous epithelium in fibrous stroma and is classified as a benign epithelial odontogenic tumor by the World Health Organization (WHO) [2]. Most SOTs are ‘central SOTs’, that is, they are located within maxillary or mandibular bone and exhibit a slight mandibular preference [3].

    Radiographically, SOTs usually are observed as unilocular, triangular or semicircular radiolucencies between or along the roots of adjacent teeth. SOTs may be symptomatic and when present, symptoms can include tooth mobility, tooth displacement with gingival swelling, increased periodontal pocket depth, and mild to moderate pain [4]. Most SOTs are relatively small lesions [2.2cm(mean) ± 1.4(SD), min:0.5, max:7.0; n = 85][5].

    Here, we report a case of a large squamous odontogenic tumor located in the right posterior maxilla with unusual radiographic and clinical appearances.

    Ⅱ. CASE REPORT

    A 60-year-old woman visited the Department of Oral and Maxillofacial Surgery at the Pusan National University Dental Hospital (Yangsan, South Korea) in March 2018 with gingival discomfort in the right posterior maxillary region. Her right maxilla second molar (#17) had been extracted at other private clinic before 10 days previously. The patient had no underlying disease. Intraorally, there was a mild swelling of vestibular and palatal mucosae (Fig. 1).

    1. Radiographic findings

    Orthopantomographic x-ray (OPTG) depicted a well-defined multilocular radiolucent lesion in the right maxillary posterior region (Fig. 2), and this finding was confirmed by cone beam computed tomography (CBCT). Buccal bone was expanded and thinned by the lesion, which had also perforated crestal and buccal bone in the right maxilla (Fig. 3). The lesion measured about 4.5cm in diameter. These radiologic findings overlapped with odontogenic keratocyst and ameloblastoma, which appear as a multilocular radiolucent lesion with marked cortical perforation or expansion. Accordingly, the differential diagnosis included odontogenic keratocyst and ameloblastoma.

    2. Intra-operative & post-operative findings

    Complete excision of the lesion was planned under general anesthesia. A buccal approach to the lesion was used and yellowish, hard mass of diameter ~4.5 cm was observed (Fig. 4). In addition, buccal bony wall perforation was identified with no resorption of the right maxilla first molar (#16). The lesion was complete excised while preserving the Schneiderian membrane, and this was followed by primary closure.

    The patient underwent follow-up on postoperative day (POD) 10. Despite the absence of clinical symptoms, wound dehiscence was observed in the right maxilla second molar (#17) extraction site. The maxillary first molar exhibited no mobility.

    Although a small oroantral fistula remained on POD 20, there was no evidence of infection or Schneiderian membrane perforation. Furthermore, there were no clinical symptoms and the patient had no complaints.

    Operative site had healed at 2 months after lesion excision without any sequelae like dehiscence or infection. According to a CBCT assessment performed at 1 year postoperatively, there was no sign of recurrence, and no buccal bone rebuilding was observed in the posterior right maxillary region.

    3. Pathologic findings

    At the time of initial referral, and incisional biopsy was performed under local anesthesia. Histopathologic examination revealed multiple islands of bland-appearing squamous epithelium in fibrous stroma (Fig. 5), indicating the presence of squamous odontogenic tumor. A histopathologic examination was also performed on the excised lesion and revealed scattered islands of squamous epithelium in dense fibrous connective tissue stroma. Reverse polarization of cell nuclei was not observed (Fig. 6). The diagnosis of squamous odontogenic tumor was confirmed by the Department of Clinical Pathology at the College of Medicine, Pusan National University.

    Ⅲ. DISCUSSION

    Squamous odontogenic tumor was initially described and named in 1975 by Pullon [6], before which it was believed to represent acanthomatous ameloblastoma or even squamous cell carcinoma [7]. According to the WHO classification of head and neck tumors (2017), SOT is a locally infiltrative neoplasm consisting of islands of well-differentiated squamous epithelium in fibrous stroma [2].

    SOT is distributed evenly between mandibles and maxillae with a slight mandibular predilection [3]. Maxillary SOTs are mostly encountered in the anterior region and are notably more aggressive [8-12], probably because of the low bone density of maxillae [8]. SOT does not exhibit a sex or race predilection.

    Clinically, SOT is slow growing lesion that can cause bone expansion, tooth mobility, painful symptoms, and tooth displacement, but it may also be asymptomatic. Most examples of asymptomatic lesions are relatively small with greatest diameters seldom exceeding 1.5 cm [7]. Excision is most commonly used to treat SOT. A few cases of recurrence have been reported after complete excision. Chrcanovic BR et al. (2018) [5] reviewed 74 articles that included a total of 110 SOT cases (102 central, 8 peripheral). 4 of 54 central SOT cases known to be treated by complete excision recurred. Although complete excision is the most frequently described treatment method, it should be tailored based on the clinical and radiographic lesion extents. According to Chrcanovic’s review, average lesion size was 2.2 cm (mean) ± 1.4 (SD) (min: 0.5cm, max: 7.0cm; n = 85.

    Radiographically, SOT is usually visualized as an irregularly or triangularly shaped, unilocular radiolucent lesion adjacent to the roots of teeth or superior alveolus. Chrcanovic’s et al. reported root resorption in only 4 of 88 cases [5]. Lesions are usually located in within jaw bone(“central SOT”), but sometimes may not be (“peripheral SOT”)[13,14].

    Histologically, SOT exhibits islands of bland-appearing squamous epithelium in mature connective tissue stroma. Some microcysts are sometimes observed within epithelial islands, and peripheral cells in these islands do not show the typical reverse polarization of ameloblastomas. Thus, lack of reverse polarization is a differential criterion favoring SOT. Pathologists can misclassify SOT as ameloblastic fibroma, but ameloblastic fibroma tends to occur in younger patients and histologically exhibits islands of narrow, long cords of odontogenic epithelium.

    The described case is unusual because the lesion was located in the posterior maxillary region, which is rare. Before incisional biopsy of the lesion, we diagnosed ameloblastoma or odontogenic keratocyst based on the visualization of radiographic multilocular radiolucency. Notably, at the time of excision, the lesion presented as a yellowish, hard mass of diameter 4.5 cm. Histologic examination revealed scattered islands of squamous epithelium in dense fibrous connective tissue stroma without reverse polarization of cell nuclei or narrow cords of odontogenic epithelium. Small microcysts were also seen within epithelial islands

    Treatment was conducted by complete lesion excision. The patient was followed-up weekly for 2 months. The surgical wound healed without OAF or complication at 2 months postoperatively, and there was no sign of recurrence and of buccal bone rebuilding in the right posterior maxillary area at 1 year postoperatively. Recurrence after complete excision and when encountered can be attributed to incomplete tumor removal [15].

    This report presents a rare case of a large squamous odontogenic tumor with unusual radiographic and clinical features and adds to the literature on squamous odontogenic tumor.

    ETHICS APPROVAL AND CONSENT TO PARTICIPATE

    This case report was reviewed by the Institutional Review Board (IRB) of Pusan National University Dental Hospital and was approved from deliberation(PNUDH-2019-015).

    Figure

    KAOMP-43-4-115_F1.gif

    Intraoral photographs at initial presentation. Extraction site on right maxilla second molar and mild gingival swelling of the right maxillary posterior region.

    KAOMP-43-4-115_F2.gif

    Panoramic radiograph demonstrates the multilocular radiolucent nature in the right maxillary posterior region.

    KAOMP-43-4-115_F3.gif

    The lesion visualized by cone-beam computed tomography exhibits buccal-palatal bone expansion, thinning(A) and perforation(B) by the lesion.

    KAOMP-43-4-115_F4.gif

    Intraoperative photographs. A: Complete excision of the squamous odontogenic tumor with preservation of the Schneiderian membrane. B,C: Yellowish and hard mass which was about 4.5cm in diameter.

    KAOMP-43-4-115_F5.gif

    Histopathological view after incisional biopsy. A: Histopathological picture showing odontogenic epithelial islands in mature fibrous stroma, B: On higher magnification, multiple islands of bland-appearing squamous epithelium and lack of reverse polarization of the nuclei of the cells are evident.

    KAOMP-43-4-115_F6.gif

    Histopathological view after complete excision. A: Histopathological picture showing odontogenic epithelial islands in mature fibrous stroma, B: On higher magnification, multiple islands of bland-appearing squamous epithelium and lack of reverse polarization of the nuclei of the cells are evident.

    Table

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