Ameloblastoma of the jaws: A critical reappraisal based on a 40-years single institution experience
Doenja Hertog, Isaäc van der Waal
*Department of Oral and Maxillofacial Surgery/Oral Pathology, VU University Medical Center/Academic Centre for Dentistry (ACTA), Amsterdam, The Netherlands
a r t i c l e i n f o
Article history:
Received 14 September 2009
Received in revised form 5 November 2009 Accepted 6 November 2009
Available online 9 December 2009
Keywords:
Odontogenic tumours Ameloblastoma
s u m m a r y
The 40-years of experience in a single institution with the treatment of previously untreated ameloblas- toma have been reported, followed by a management protocol. Retrospectively, 25 consecutive patients treated between 1969 and 2009 have been analyzed. In 11 patients, a preoperative diagnosis of amelo- blastoma was available. In the remaining 14 patients the diagnosis of ameloblastoma was a postoperative one. For the recurrence rate a minimum follow-up period of 5 years was observed; 20 patients met these criteria.
After primary radical surgery in five patients, no recurrences were observed. In case of conservative surgical treatment, performed in 15 patients, a recurrence was observed in eight (53%) of them. Six of these patients were then treated successfully by radical surgery, while two patients refused such surgical approach. In one of the patients with a recurrence a cervical lymph node metastasis was detected at the same time, resulting in a diagnosis of metastasizing ameloblastoma.
Ó 2009 Elsevier Ltd. All rights reserved.
Introduction
In the World Health Organization Classification of Odontogenic Tumours a distinction is made between benign ameloblastoma and malignant ameloblastoma.1Within the group of benign ameloblas- tomas four subtypes are recognized, being the solid/multicystic, the desmoplastic, the unicystic and the extraosseous/peripheral type, respectively.1By far the majority of ameloblastomas are lo- cated within the jaw bones. The peripheral ameloblastoma is ex- tremely rare, indeed. This type will not be discussed here any further.
Malignant ameloblastomas are extremely rare; in the WHO classification two main subtypes are recognized, being (1) the metastasizing ameloblastoma and (2) ameloblastic carcinoma.
The estimated incidence of ameloblastomas is approximately 0.5 per million population per year. There is no distinct gender pre- dilection. Most cases are diagnosed between 30 and 60 years of age. Unicystic ameloblastomas are more common under the age of 20 years.2 There are no well established etiologic factors. The posterior region of the mandible is the site of predilection. In approximately 40% of the cases there is an associated unerupted tooth, often the mandibular third molar. Ameloblastomas may re- main asymptomatic before a facial swelling develops.
Ameloblastomas may present on conventional radiographs as a unilobular or multilobular corticated radiolucency resembling a cyst. Bony septae may result in a honeycomb appearance. Buccal and lingual expansion is more common in ameloblastoma than in keratocystic odontogenic tumours.3Resorption of roots may or may not be present. The radiographic differential diagnosis in- cludes a variety of odontogenic cysts, a keratocystic odontogenic tumour, an odontogenic myxoma, as well as non-odontogenic tu- mours and cysts, such as a central giant cell granuloma and a sim- ple bone cyst, respectively. Computed tomography and MRI may be helpful in establishing the extent of the lesion, particularly when located in the maxilla.
The preferred treatment of ameloblastoma is wide surgical re- moval with the possible exception for unicystic ameloblastoma, as will be discussed later.
In this study the 40-years single institution experience with the management of primary ameloblastoma will be reported and dis- cussed in relation to the present concepts of this odontogenic tumour.
Patients and methods
Twenty-five consecutive patients, 14 men and 11 women, diag- nosed with a histologically benign, previously untreated amelo- blastoma at the Department of Oral and Maxillofacial Surgery between September 1969 and September 2009 have been in- cluded. The information retrieved from the files included age, gen- der, localization, preoperative diagnosis, histopathological subtype, 1368-8375/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.oraloncology.2009.11.002
* Corresponding author. Address: Department of Oral and Maxillofacial Surgery/
Pathology, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands. Tel.: +31 20 444 4039; fax: +31 20 444 4046.
E-mail address:i.vanderwaal@vumc.nl(I. van der Waal).
Oral Oncology 46 (2010) 61–64
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type of surgery and follow-up information (Table 1). In 11 patients, a preoperative diagnosis of ameloblastoma was available. They all were advised to have radical surgery; three of them refused such treatment and have been treated by enucleation, instead. In the remaining 14 patients the diagnosis of ameloblastoma became apparent only after conservative surgical removal.
Routine follow-up consisted of annual clinical and radiographic examination, occasionally extended with CT-scans or MRI in cases of maxillary involvement, up to a period of at least 10 years. One patient primarily treated by radical surgery was lost to follow-up after 3 months due to refusal of the patient. With regard to treat- ment results only patients with a minimum follow-up period of 5 years were included; 20 patients fulfilled these criteria.
In the same period, 11 patients with a recurrent ameloblastoma have been observed who had been treated elsewhere previously.
Furthermore, one patient with a primary malignant ameloblas- toma has been recorded; one other patient was noticed with a peripheral ameloblastoma. These latter two patients will not be discussed here any further.
In view of the small number of patients no statistical analysis has been performed.
Results
These results are summarized inTable 2. Of the 20 patients who had been followed-up for at least 5 years, local recurrence was ob- served in eight (53%) of the 15 patients who had been treated by enucleation, seven of them within 5 years and one after 8.3 years.
Six of these eight patients have additionally been treated by radical surgery; no second recurrences were observed in this group of pa- tients during a mean follow-up period of 6.3 years. However, in one of these six patients a metastatic lymph node was detected during the reconstruction of the mandible, resulting in a diagnosis of metastasizing ameloblastoma. This patient has been discussed in detail elsewhere.4Two patients with a recurrence after enucle- ation refused radical surgery and were again treated by conserva- tive surgery. Both patients experienced multiple recurrences thereafter.
In the five patients who had been initially treated by radical surgery and being followed for at least 5 years, no recurrences were observed.
Discussion
The demographic data of the presently reported patients are more or less in accordance with those obtained from the literature.
Three patients with a unicystic ameloblastoma were observed; in only one of these patients the cystic lesion could be removed as an entirely intact specimen without any fragmentation during re-
moval. In one patient, a desmoplastic ameloblastoma was ob- served. In one other patient a metastasizing ameloblastoma was diagnosed; the metastatic cervical lymph node was detected as an incidental finding during reconstructive surgery of the mandible because of a local recurrence 8 years after enucleation of a histo- logically benign ameloblastoma.
Treatment
In the present series a preoperative diagnosis of ameloblastoma was obtained in 11 of 25 patients. Of these 11 patients three re- fused to undergo radical surgery. In the remaining 14 patients the diagnosis of ameloblastoma became available only after enu- cleation of a unicystic or multicystic/solid lesion. In none of these 14 patients immediate additional radical surgery has been performed.
There are no randomized trials of solid/multicystic ameloblas- toma with regard to the type of surgical treatment, varying from simple enucleation, marsupialisation followed by resection or curettage,5to aggressive removal, including a margin of one tissue plane in soft tissues when cortical perforation is present, clinically or radiographically.6In general, resection with a 1.5–2 cm margin beyond the radiological limit seems a safe procedure for the so- lid/multicystic type.7 Nevertheless, the debate on the preferred treatment is ongoing.8,9In our institution, we have adopted a more aggressive surgical approach in the last decade, probably influ- enced by the excellent results of immediate reconstruction of the jaws and the strongly improved possibilities of prosthetic rehabil- itation by the use of dental implants.
For the reporting on ameloblastomas it seems acceptable to group the treatment regimens into three modalities, being (1) con- servative (includes enucleation and curettage), (2) marsupializa- tion, and (3) radical surgery (includes resection with or without continuity defect).
In case of a preoperative diagnosis of solid/multicystic amelo- blastoma in children, it is tempting, mainly for psychosocial rea- sons, to perform less aggressive surgery. Furthermore, some authors have suggested that ameloblastomas in children may be- have less aggressively.10At the same time, one may advocate not to be less aggressive in view of the high recurrence rate after con- servative surgery and the long life expectancy at childhood.
In case of a unicystic ameloblastoma, based on an incisional biopsy, some authors recommend decompression followed by enu- cleation within 3–4 months.11–13However, a preoperative biopsy in unicystic ameloblastoma is not always representative14; in fact, Ackerman et al. recommend not to perform such an incisional biopsy in these circumstances.15In the past, unicystic ameloblasto- mas have been reported to behave less aggressively than the solid/
multicystic type.16However, in several recent studies this view has been challenged.6,17,18
Little is known about the role of postoperative radiotherapy in case of incomplete removal.19 There are no reliable data about the possible value of additional treatment modalities such as the use of liquid nitrogen or tissue fixatives such as Carnoy’s solution,6 although such practice is recommended by some authors.11,12 Table 1
Characteristics of 25 patients.
Gender Male 14
Female 9
Age (in years) 34.4 (range 12–70)
Localization Mandible 20
Maxilla 5
Diagnosis Preoperative 11
Postoperative 14
Histological subtype Follicular 10
Plexiform 7
Follicular/plexiform 4
Desmoplastic 1
Unicystic 3
Type of surgery Conservative 17
Radical 8
Table 2
Recurrence in patients with a minimum follow-up period of five years (n = 20).
Type of treatment Number of
patients
Recurrence (%) Conservative surgical removal (includes
enucleation and/or curettage)
15 8*(53%)
Radical surgical removal 5 – (–)
*In one patient a cervical lymph node was encountered, resulting in a diagnosis of metastasizing ameloblastoma.
62 D. Hertog, I. van der Waal / Oral Oncology 46 (2010) 61–64
Recurrence
Eight of the 15 (53%) patients, primarily treated by enucleation and followed-up for at least 5 years, developed a recurrence of whom six were additionally treated by radical surgery; no second recurrences were observed in these six patients during a mean fol- low-up period of 6.3 years.
In a large series reported from South Korea, the follicular, gran- ular cell and acanthomatous types had a relatively high likelihood of recurrence, while the desmoplastic, plexiform and unicystic types showed a relatively low potential for recurrences.10However, in the meta-analysis from Pogrel and Montes the histopathological subtypes, including unicystic ameloblastomas, did not seem to be relevant in this respect.6Partly based on our own experience, but also based on a number of large studies performed by others, the chance of recurrence seems to be more dependent on the method of surgical treatment rather than the histological subtype.20 Follow-up regimen
In our series, most recurrences were observed within a follow- up period of 4 years. In general, annual follow-up for at least 10 years is recommended. Others recommend annual follow-up until 5 years and every 2 years thereafter for at least 25 years.11,21
For the mandible the use of a panoramic view seems adequate.
Unfortunately, the panoramic view is not very suitable for the detection of a possible recurrence in the maxilla or the maxillary sinus. In fact, in this location CT-scans are by far superior. In order to eliminate ionizing radiation exposure MRI may be an ever better imaging tool for maxillary lesions.
Management protocol
Based on the experiences reported in the literature and also on our own experience a treatment protocol has been proposed in Table 3.
Conflict of Interest Statement None declared.
References
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Table 3
Management of benign ameloblastoma.
Comments:
1. The limited amount of tissue obtained during marsupialization may histopathologically not be representative for the entire lesion.
2. The use of fresh frozen sections for establishing a possible diagnosis of ameloblastoma is discouraged.
3. There is insufficient evidence that ameloblastomas in children can be treated less aggressively than in adults.
4. There is insufficient evidence to advice the use of adjunctive treatment, such as liquid nitrogen or Carnoy’s solution, after surgical removal of an ameloblastoma 5. A ‘‘wait-and-see” policy after conservative removal of a multicystic/solid ameloblastoma in the body/symphysis region of the mandible or the anterior maxilla (between the first molars) is discouraged, since this policy carries the risk of uncontrollable disease.
6. The remote risk of regional or distant metastases (e.g. lungs) does not warrant routine studies for such events at follow-up.
7. Radiotherapy should only be considered in uncontrolled disease.
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