原文題目

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口腔病理科 On-Line KMU Student Bulletin

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原文題目(出處)： Unusual presentation of localized gingival enlargement associated with a slow-growing odontogenic myxoma. Int J Oral Sci 201;5:172-5

原文作者姓名： Rius JM, Nadal A, Lahor E, Mtui B, Brunet L

通訊作者學校： Departament d’Odontostomatologia, Facultat d’Odontologia, Universitat de Barcelona, Barcelona, Spain

報告者姓名(組別)： Intern G 組王雅羽

報告日期： 2014/02/11

內文：

一. Introduction

1. Gingival enlargement is defined as an abnormal growth of the gum tissue, associated with multiple factors including: inflammation, hormonal, drug use, neoplasm, genetic, systemic and idiopathic.

2. Odontogenic myxoma (OM) is a benign, locally invasive and aggressive, non-metastasizing neoplasm of the jaw bones, represent approximately 3%–20% of all odontogenic tumours. As it is often asymptomatic, the lesion may reach a considerable size before the patient discovers its existence.

3. According to the WHO classification odontogenicmyxoma/myxofibroma, is composed of cells from the mesenchyme and/or odontogenic ectomesenchyme with or without odontogenic epithelium. Macroscopically OM has a whitish, translucent, mucinous appearance. It is uncapsulated and poorly demarcated. This tumour has a low proliferation rate.

4. Histopathologically, myxoma and/or myxofibroma are characteristically hypocellular. Microscopically these lesions are characterized by stellate and spindle-shaped cells embedded in a richly myxoid extracellular matrix, with little collagen.

5. Radiographically, the tumour is seen as a unilocular or multilocular radiolucent lesion with well-defined borders, some of them having sclerotic trabeculations with different appearances. Displacement of teeth is a relatively common finding, although root resorption is rarely seen.

6. Current treatment ranges from curettage to block resection with wide margins with different rates of recurrence.

二. Case report

1. A 55-year-old black male was attended at Dental & Oral Department

in Soweto General Hospital, Arusha (Tanzania), complaining of a growing swelling in the area of the anterior left mandible for more than ten years, involving the incisors and canine region (from 33 to 41). He had neither smoking history nor other past medical history of note.

2. This extreme localized gingival enlargement measured 28mm × 33mm in diameter with very well-defined contour and spherical shape. Mucogingival line was completely preserved. Painless and lesion size made difficult a correct lip-seal, caused gingival trauma during mastication and induced local tooth displacement .No dental mobility was noted and dental vitality was normal. A moderate chronic periodontitis

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Clinical appearance (from 33 to 41)

3. Radiographically, there was an unilocular radiolucent lesion, inducing

root displacement without resorption, between 33 and 32 teeth with well-defined borders suggesting a cystic, ‘soap bubble’ lesion. CT was performed, showing an expansive and osteolytic single left mandibular lesion, with buccal and lingual cortical bone destruction .

4. The radiology report informed an odontogenic keratocyst. A conservative surgery with enucleation and curettage was performed without preoperative biopsy.

Buccal cortical was completely effaced. After a thoroughly curettage of the quite soft tumoural tissue an important infrabony defect appeared which caused a considerable denuded radicular surface of the involved teeth.

5. The whole defect was filled using a mixture of the bone previously collected and a bone graft substitute Straumann Bone Ceramic (porous biphasic calcium phosphate). Some reabsorbable haemostat chips of Collagen Diacoll (Collagen of porcine origin) were also used to stabilize this mixture. After 12-month follow-up, no evidence of recurrence was found.

6. Tissue submitted for histopathological analysis consisted of several

soft pieces that altogether measured up to 25 mm × 15 mm × 5mm with a gray-whitish, translucent, mucinous appearance including an osseous fragment 4 mm

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long.

7. Microscopically, the lesion was made up of an abundant loose mucoid or myxoid stroma with evenly distributed round cells with scarce randomly oriented spindle- or stellate-shaped cells of mesenchymal origin alternating with more highly cellular areas and eosinophilic areas of collagen deposition.

8. No cyst lining was found. Neither cellular pleomorphism, nor multinucleated cells, nor mitotic activity nor epithelial odontogenic rests were seen.

Residual lamellar bone fragments were interspersed within the myxoid stroma. All these features rendered the histopathological diagnosis of odontogenic myxoma/myxofibroma.

三. Discussion

1. Odontogenic myxoma exhibits slow and asymptomatic expansion, sometimes resulting in a perforation of the cortical borders of the bone affected. Radiological examination plays a crucial role for the differential diagnosis of OM, which includes other pathological conditions like: odontogenic fibroma, fibrous dysplasia, ameloblastoma, dentigerous cyst, odontogenic keratocyst, central giant cell granuloma, osteosarcoma, fibrosarcoma, ossifying fibroma and chondrosarcoma.

2. OMs can be found in several areas in both jawbones, the mandible is affected more frequently than the maxilla, and the posterior region is the most frequently affected location in both sites.

3. The treatment of OMs has been most controversial. Radical resection or conservative tumour excision is depending on tumour size.

4. The recurrence after resection seems to be noticeably lower than after enucleation and curettage. The suggested treatment by some authors is to perform a conservative surgery by enucleation and curettage when lesions are smaller than 3 cm and segmental resection with immediate reconstruction when bigger lesions are present.

5.Some authors use different bone grafts or allograft materials for filling residual bone defects after surgery. The autologous bone graft has ostoinductive, osteoconductive and osteogenetic properties and prevent from any possible viral infections transmission. Fresh-frozen human bone processed by the Tissue Bank, which provides osteoinductive and osteoconductive properties with major availability of bone for filling defects, can be considered a safe choice.

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6. Myxomas/myxofibromas show a recurrence rate between 25% and 43%.

These recurrences are the result of local invasion into cancellous bone beyond radiographically visible margins in the absence of encapsulation. The nature of this lesion, without a sheath but with an infiltrative growth of the myxomatous tissue into the adjacent bone, determines the high rate of relapse when conservative enucleation and curettage are performed.

7. Other odontogenic tumours, like the keratocyst or the ameloblastoma show higher recurrence rates of 30%–58.3% and 55%–90%, respectively. These patients should be monitored for at least 2 years after the surgical intervention due to the higher rate of recurrence during this period.

題號題目

1 Which statement is true?

(A) Myxoma my be found more commonly in mandible.

(B) The lesion of myxoma is painful.

(C) Myxoma is predominantly found in old male.

(D) Radiographically, the myxoma appears as a radiopaqe image.

答案(A) 出處：Oral and Maxillofacial Pathology 3^rd edition, Neville, et al p.730

題號題目

2 Which statement of treatment and prognosis of myxoma is true?

(A) Metastasis usually occurred.

(B) Small myxomas are gemerally treated by curratage.

(C) Recurrence rate approximately 60％.

(D) Recurrence rate approximately 90％.

答案(B) 出處：Oral and Maxillofacial Pathology 3^rd edition, Neville, et al p.731