| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
CASE REPORT |
1 Department of Oral and Maxillofacial Radiology, Field of Tumor Biology, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan; 2 Department of Oral and Maxillofacial Radiology, College of Dentistry Kyung Hee University, Japan
*Correspondence to: Jun-ichi Asaumi, Department of Oral and Maxillofacial Radiology, Field of Tumor Biology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Science, 2-5-1, Shikata-cho, Okayama-city, Okayama, 700-8525, Japan; E-mail: asaumi{at}md.okayama-u.ac.jp
Received 14 February 2005; revised 4 April 2005; accepted 2 May 2005
 |
Abstract |
|---|
 Top Abstract Case reportDiscussionReferences |
|---|
Keywords: recurrence; ameloblastoma; bones; grafts
|
Case report |
|---|
|
TopAbstractCase reportDiscussionReferences |
|---|
) and occlusal (Figure 1b, left) radiographs showed a multilocular radiolucency with a well-defined margin in the mandibular body. There was also an expansion and thinning of the lingual cortical bone. Histopathological features by biopsy revealed extensive squamous metaplasia associated with keratin formation in the central portions of the epithelial islands of a follicular ameloblastoma. Therefore, the lesion was diagnosed as an acanthomatous ameloblastoma with a follicular pattern (Figure 1e, upper). Partial mandibulectomy safely securing a bony margin was performed through an intraoral approach, and the surgical defect of the mandible was primarily reconstructed with a free iliac crest bone graft (Figure 1a, centre). The patient had good post-operative course except for anaesthesia of the right lower lip. Since he had no evidence of recurrence in clinical and radiographic examination for 5 years, he ceased coming to our hospital.
|
) and occlusal (Figure 1b, right) radiographs showed a large multilocular radiolucency occupying the whole graft bone with a relatively well-defined border. Computed tomography (CT) showed expansion of the tumour mass to adjacent soft tissue at the buccal side and thinning, expansion and perforation of the cortical outline of the graft bone with multilocular radiolucency (Figure 1c).
Magnetic resonance (MR) examinations were performed using a 1.5-tesla unit (Magnetom Vision; Siemens, Erlangen, Germany). T1 weighted spin-echo sequences (T1WI: repetition time (TR)/echo time (TE)=660/15), T2 weighted fast-spin-echo with a fat-suppression technique (T2WI: TR/TE=3000/90) and T1WI using a fat suppression technique 15 min following the contrast material (CE-T1WI) (Gd-DTPA, Magnevist; Nihon Schering, Osaka, Japan) administration were obtained. Regarding signal intensity (SI), a signal from the musculature was interpreted as intermediate on T1WI, and a signal from the cerebrospinal fluid as very high on T2WI. The tumour mass was revealed as intermediate SI on T1WI, heterogeneous high SI with more high SI area on T2WI and disproportioned SI enhancement including no enhanced spot on CE-T1WI. Tumour extension to the adjacent soft tissue was revealed on the buccal and lingual side (Figure 1d).
The patient was diagnosed with recurrent ameloblastoma by biopsy. Therefore, a right partial mandibulectomy was performed with the surgical margin extending into the overlying soft tissue. Histopathological features of the surgical specimen revealed the combination of a follicular and plexiform microscopic pattern. It also demonstrated cystic degeneration, particularly at both the central portion of the follicle pattern and the stroma of the plexiform pattern (Figure 1e, lower). There was no recurrence at the 1-year follow-up examination after surgery.
|
Discussion |
|---|
|
TopAbstractCase reportDiscussionReferences |
|---|
Ameloblastoma occurs in three different clinicoradiographic situations: the solid or multicystic (the classic intraosseous ameloblastoma), the unicystic, and peripheral varieties.1,9,17,18 The recurrence rates show that the solid or multicystic variety has the greatest propensity for local infiltration and therefore the highest potential for recurrence among the three varieties.7–10,19,20 Examinations of growth characteristics of the solid or multicystic ameloblastomas and the reaction of the surrounding tissues frequently show infiltration to the cancellous bone but little tendency to invade the cortical bone.9,18,20 The periosteum can adequately prevent extension of the tumour. This infiltration of cancellous bone has important consequences clinically.9 On the other hand, the dense compact bone of the inferior border of the mandible and the ascending ramus acts as an effective barrier to prevent the tumour's spread.17,21,22 These clinopathological characteristics and treatment considerations could be applied to the cases of recurrent ameloblastoma involving autogenous bone graft. In our case, the primary tumour revealed infiltration to the cancellous bone, forming a honeycomb appearance, and perforation of lingual cortical bone appearing on radiograph. Although the large recurrent tumour occurred in the iliac graft bone, the remaining mandibular stump was regarded as preserving an intact bony outline and preventing the tumour from spreading.
The radiographic imaging of an ameloblastoma varies according to the stage of its development and whether it has perforated into adjacent soft tissues. There is a greater tendency for advanced cases to develop a configuration suggestive of compartments in the bone separated by distinct septa that reach into the radiolucent area. In some cases, the number and arrangement of septa may give the area a honeycomb or soap bubble appearance. In advanced cases, the cortex has eroded in one or more areas, and the perforated cortical plates may contribute to a multilocular appearance.23 CT not only suggests the diagnosis and demonstrates the anatomic location of a lesion but also helps to detect encroachment into such vital regions as the floor of the mouth, infratemporal fossa and the submandibular region.24,25 In the case reported here, CT provided excellent and detailed images of both hard and soft tissue, but on the axial images of the occlusal plane, metallic artefact degradation led to inaccurate interpretation of the posterior tumour margin. In MRI, pathological tissues demonstrated an intermediate SI on T1WI and high SI on T2WI. Especially, T2WI provided better edge definition and conspicuity, allowing for more precise description of the interface between tumour and normal tissue. The contrast-enhanced images were also very useful in understanding histopathological changes and the composition of the tumour as cystic degeneration.
Histopathologically, in our case, the primary tumour showed an acanthomatous pattern with extensive squamous metaplasia, associated with keratin formation, occurring in the central portions of the epithelial islands of a follicular ameloblastoma. However, the recurrent tumour showed a combination of follicular and plexiform microscopic patterns. This phenomenon explains that the acanthomatous pattern is merely a histological variant of the follicular pattern in which the stellate reticulum is replaced by squamous cells.25 The pathogenesis of recurrent ameloblastoma involving a bone graft is not easy to explain. The phenomenon is not strictly related to an ameloblastoma, because cases of myxoma and odontogenic keratocyst recurring in bone grafts also have been reported.26,27 Hypothetical origins have been suggested to explain these recurrences: occurrence from the mandibular stump, the adjacent soft tissues, and intraoperative contamination.12,23 The first hypothesis, that recurrence originates in the residual mandibular stump, is considered unlikely because sufficient bone resection has generally been performed in cases of treatment accompanied by autogenous bone graft. The second hypothesis, that recurrence involving a bone graft is derived from soft tissue recurrence, has been supported by several authors11–16,29 on the basis of their observation that the site of recurrence is relatively distant from the junction of the graft with the adjacent bone. Finally, intraoperative contamination as a seeding in the graft bone of the tumour cell should be considered the most important or likely causative factor in recurrence of ameoblastoma in bone grafts.15,23,29 This hypothesis also may be supported from the fact that the occurrence of ameloblastoma at the iliac bone of the donor site for bone graft has been reported.30
In our case, seeding to the graft bone is suspected as the cause of recurrence in the iliac bone graft because wide destruction of the graft bone without preceding signs and symptoms of intraoral mucosa was observed. However, the iliac bone used as graft bone has a weakness as anatomical barrier for resistance to tumour infiltration. Therefore, recurrence from soft tissue cannot be excluded. These recurrent lesions must be considered dangerous because they can lead to failure of the bone graft. The average period between the initiation of recurrent ameloblastoma and its detection is unknown. Reichart et al8 reported that, on the average, patients noted clinical symptoms 2.3 years before the first diagnosis was made. Ameloblastomas grow slowly; it could be 2 or 3 years or more, before the tumour is detected clinically in the case of solid or multicystic ameloblastomas and unicystic ameloblastomas. Consequently, the growth of the tumour might be initiated about 4 or 5 years before diagnosis is made.9 In our case, assumptions about the initiation of the tumours are difficult because the patient forfeited the function of sensation for early detection of tumour growth. Moreover, after surgery the grafted bone undergoes resorption and osteoporotic remodelling.31 For this reason, the role of an anatomic barrier, such as that played by the cortical bone of mandible, is deficient. Nevertheless, the delayed recurrence of our case, 20 years after surgery of the primary tumour, showed extensive bony resorption extending through the whole auto-grafted bone. Consequently, persistent follow up examination is essential for management of ameloblastoma.
|
References |
|---|
|
TopAbstractCase reportDiscussionReferences |
|---|
This article has been cited by other articles:
 |
|
 |
|
  A Auluck, S Shetty, R Desai, and M Mupparapu Recurrent ameloblastoma of the infratemporal fossa: diagnostic implications and a review of the literature Dentomaxillofac. Radiol., October 1, 2007; 36(7): 416 - 419. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Martins A case of recurrent ameloblastoma developing in an autogenous iliac bone graft. Dentomaxillofac. Radiol., September 1, 2006; 35(5): 390 - 390. [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| BJR | DMFR | IMAGING | ALL BIR JOURNALS |
