This information has been written for patients, their families and friends and the general public to help them understand more about a rare benign (non-cancerous) tumour known as ameloblastoma. This section will detail what an ameloblastoma is and how ameloblastomas can be diagnosed and treated.
For a downloadable source of this information, please view our 'Downloadable Information Materials' page to view all of our fact sheets.
Ameloblastoma is a rare tumour which involves excess tissue growth in and around the jaw. This tumour is usually benign (non cancerous) and can appear to be solid or cyst-like. It is important that this non-cancerous tumour is diagnosed early in order to prevent its excessive growth, bone destruction and possible progression to a cancerous tumour.
Ameloblastoma is a rare, benign, tumour of the bone which can occur in the lower or upper jaw bone. It is very common for this tumour to occur around the position of the third molar tooth (known as the wisdom tooth). These tumours occur most frequently in the lower jaw bone (known as the mandible), with approximately 80% of reported ameloblastomas occurring here. The remaining 20% of cases occur in the upper jaw bone (known as the maxilla), or present in both the mandible and the maxilla simultaneously(1).
Although ameloblastomas tend to be slow-growing, non-cancerous, tumours they can occasionally become aggressive and affect tissues surrounding the jaw area, such as the sinuses or eye-sockets as well as nerves and blood vessels. We describe this behaviour as ‘locally aggressive’, which can cause swelling and bone destruction at the site of the ameloblastoma. As this tumour type originates in the tissues that give rise to teeth, bone destruction can result in some facial distortion(2,3).
Statistically, only 1% of all jaw tumours are ameloblastomas and in most cases the growth is benign (non-cancerous) and non-metastatic (they do not spread). The risk of the tumour spreading to other areas of the body is very low, at less than 2%, but if spread does occur it is most likely to be to the lungs, the lymph nodes, the brain or the skin(1,4,5).
The spread of an ameloblastoma to elsewhere in the body can occur over a decade after treatment has taken place, and unfortunately, this rare tumour type has a relatively high risk of the tumour returning at a later date; which is known as tumour recurrence.
Ameloblastoma is known to affect males and females in equal proportions and can affect any age group or ethnicity.
Although ameloblastoma can occur at any age, it is most frequently seen in patients of around 30 to 40 years of age and is relatively uncommon in children under the age of 10 years old(5).
Ameloblastoma patients often experience no symptoms until the tumour is of a larger size. Doctors describe this as being ‘asymptomatic’. Therefore, in many cases, this rare tumour type is discovered during routine dental X-rays before the patient has experienced any symptoms(1,5,6).
The symptoms of ameloblastoma which are most commonly reported are:
- An abnormal growth in the jaw or sinus area
- Painless swelling in the jaw
- Bone pain – which may be continuous or come and go
- Delayed tooth eruption
- Loose movement of multiple teeth
- Difficulty in speaking
- Obstruction of the nasal airways
- Mouth ulcerations
- Imperfect teeth positioning when closing the jaw
For more information on the symptoms or primary bone cancer please refer to our About Primary Bone Cancer information section
There are a number of different types of ameloblastoma, which can make the final diagnosis of this tumour quite difficult and increase the time taken to reach an accurate diagnosis.
There are four main types of ameloblastoma, which vary due to their different structural make-up(3,7).
These four types of ameloblastoma are:
- Multi-cystic/Conventional Ameloblastoma (also known as solid ameloblastoma)
- Uni-cystic/Cystic Ameloblastoma
- Peripheral Ameloblastoma (also known as extraosseous ameloblastoma)
- Desmoplastic Ameloblastoma
The cause of ameloblastoma is largely unknown, and due to the rarity of this tumour it is hard to assess a possible cause from the small number of cases that have been reported.
Recent research has revealed an association between the mutation of certain genes, which are involved in controlling cell growth, division and survival, and the development of ameloblastoma. Mutations in genes known as 'BRAF' and 'SMO' have been seen in over 80% of ameloblastoma cases and so further investigation into these genes is currently taking place(5,8).
Although there is currently no identifiable cause for ameloblastoma, there are risk factors that are thought to increase the likelihood of an individual developing this tumour type.
These risk factors include:
- Poor oral hygiene
- Disregard to any swelling in the jaw
Patients with different types of primary bone cancer are assessed in similar ways. For this reason, diagnostic tests are covered in more detail in our About Primary Bone Cancer information section.
This section aims to provide information on the specific details of diagnosing an adamantinoma and to discuss other conditions that may appear diagnostically similar to adamantinoma.
If patients are experiencing any of the symptoms of an ameloblastoma they should visit their GP. Diagnosis of a suspected ameloblastoma usually follows a clinical examination and an X-ray. It is very common to be referred to a bone cancer specialist for a second opinion and confirmation of the diagnosis.
Many ameloblastomas are detected at the dentist and are discovered accidentally during routine dental procedures(2). Often the tumour may appear to be an infection, causing pain and swelling in the jaw, and is treated with a course of antibiotics. It is when these symptoms are not relieved by antibiotics that a routine x-ray is carried out to further investigate the symptoms and the suspected ameloblastoma is detected.
Further tests to confirm the presence of ameloblastoma include: x-rays, CT scans, MRI scans and a biopsy of the bone.
More information on diagnostic tests, such as CT scans, MRI scans and biopsies can be found here.
A CT scan cannot definitively diagnose an ameloblastoma. However, using a CT scan alongside an MRI scan can provide important information on the exact location of the tumour and the size of the tumour. Additionally, these scans are useful for planning the treatment of individual patients and working out the best way to surgically remove the tumour(3,5).
MRI scans and X-Rays are the most effective and accurate non-invasive procedures (that do not break the skin or enter the body) for diagnosing ameloblastoma. An MRI scan can not only tell the difference between ameloblastoma and other similar conditions, but can also identify the specific type of ameloblastoma that is presenting(6).
Taking a biopsy of the bone needed to confirm the diagnosis of ameloblastoma(6). This specialist procedure takes a small sample of the tumour so it can be examined by a pathologist under a microscope.
Results from a biopsy can take up to a week to become available and they enable doctors to confirm the presence of ameloblastoma
AN ALTERNATIVE DIAGNOSIS?
When diagnosing an ameloblastoma it is important to be able to tell the difference between this rare tumour and any other benign (non cancerous), or malignant, health conditions that may cause similar symtpoms(5). It is important the correct diagnosis is made to ensure the treatment provided is suitable(2).
It can sometimes take a long time to confirm a diagnosis of ameloblastoma after a biopsy because these tumours are rare and sometimes difficult to identify. Conditions which can be the cause of particular symptoms are known as ‘differential diagnoses’.
Other conditions which can present in the same way as ameloblastoma include:
- Adamantinoma
Ameloblastomas are often referred to as the ‘adamantinoma of the jaw’, as they appear to be very similar when they are looked at under the microscope. It is the location of the tumour that allows the differentiation between these two rare primary bone cancer types(10). For more information on adamantinomas please see our information page here.
- Keratocystic Odontogenic Tumour
A keratocystic odontogenic tumour is a benign tumour of the jaw, which commonly occurs in the lower jaw much like an ameloblastoma. Patients experience symptoms of pain and swelling and the presence of cysts in the jaw, which will need treatment to remove(11,12)
- Hard Odontoma
A hard odontoma is a tumour of the dental region and therefore is diagnosed in a similar manner to ameloblastoma
- Ameloblastic Fibrosarcoma
Ameloblastic fibrosarcoma is a rare but highly malignant tumour of dental origin. The symptoms are pain and swelling of the jaw which is very similar to an ameloblastoma(13)
Due to the rarity of ameloblastoma, and therefore the smaller number of reported cases, it is difficult to work out the most effective and safest treatment for this tumour.
Research suggests that chemotherapy is of little-to-no benefit in treating this tumour type and is used purely to relieve patients’ symptoms(4,14).
Surgery
The most effective and common treatment method for ameloblastoma is the surgical removal of the tumour. Surgery can either be ‘conservative’, which attempts to retain as much tissue as possible in the area, or surgery may be ‘radical’, a more invasive procedure which requires reconstruction of the area following tumour removal(1,6).
The surgical treatment of ameloblastomas requires a ‘wide surgical margin’ in order to achieve effective and adequate surgery. A ‘wide surgical margin’ means the tumour is removed alongside a small amount of healthy tissue. This method ensures all cancerous cells are removed and lowers the risk of the tumour returning at a later date (which is known as tumour recurrence). If the tumour does return, a second round of surgery may be carried out(1,7).
On rare occasions, it may be necessary for surgeons to perform a procedure known as a ‘hemimandibulectomy’, which is the removal of part of the lower jaw(7,10).
Once the tumour has been removed, surgical reconstruction will be carried out using a metal implant or bone that is taken from elsewhere in the body; this is known as an autograft. The fibula bone is a strong bone in the leg and is often used for the reconstruction of the jaw as some of this bone can be used without affecting the function of the leg.
For more information regarding treatment procedures, including surgery and chemotherapy, please visit our About Primary Bone Cancer information page.
Outcome
Ultimately, it is highly beneficial to diagnose and treat ameloblastomas as early as possible. Early diagnosis and adequate treatment leads to an excellent outlook for patients in previously reported ameloblastoma cases. The recurrence rate for ameloblastoma is approximately 50-72% if the tumour is not fully removed during surgery, emphasising the importance of correct diagnosis and an adequate surgical procedure(4).
It is important to bear in mind that patients receiving treatment outside of the UK may receive different tests and treatment plans in accordance to the treatment guidelines set out in that specific country. If you have any questions or concerns regarding this please discuss this with your medical team or contact The Bone Cancer Research Trust for more information.
If you would like more information about ameloblastoma please contact us.
Research is being carried out to investigate genes which appear to be commonly mutated in ameloblastomas - such as BRAF and SMO genes. The mutations observed in these genes appear to be associated with a lack of control over the cells growth and division – which ultimately leads to the development of a tumour.
There are developed and approved targeted therapies to these mutations used in other tumour types. Therefore it is hoped that in the near future these targeted drugs, such as Vemurafenib which directly targets the BRAF mutation, can be tested for their efficiency in the treatment of ameloblastoma tumours (5,8).
Key References
1. Dandriyal, R, Gupta, A, Pant, S, Baweja, H.H. Surgical Management of Ameloblastoma: Conservative or Radical Approach. National Journal of Maxillofacial Surgery. 2011; 2(1): 22-27. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC330422...
2. Patel, V, Managutti, A, Menat, S, Managutti, S, Patel, J. Management of Large Mandibular Ameloblastoma Crossing Midline: Reconstructed by Bilateral Iliac Crest Graft: A Rare Entity. IJSS Case Reports and Reviews. 2015; 1(11): 58-62. Available at:
http://www.ijsscr.com/sites/default/files/articles...
3. Canger, E, Çelenk, P, Bulut, E, Günhan, Ö. An Unusual Case of Ameloblastoma Observed in the Left Anterior Mandible. The Journal of Contemporary Dental Practice. 2014; 15(6): 775-778. Available at: http://www.jaypeejournals.com/eJournals/ShowText.a...
4. Ghiam, A.F, Zahrani, A, Feld, R.A. Case of Recurrent Metastatic Ameloblastoma and Hypercalcaemia Successfully Treated with Carboplatin and Paclitaxel: Long Survival and Prolonged Stable Disease. Ecancer Medical Science. 2013; 7(323). Available at:
http://ecancer.org/journal/7/full/323-a-case-of-re...
5. More, C, Tailor, M, Patel, H.J, Asrani, M, Thakkar, K, Adalja, C. Radiographic Analysis of Ameloblastoma: A Retrospective Study. Indian Journal of Dental Research. 2012; 23(5): 698. Available at: http://www.ijdr.in/article.asp?issn=0970-9290;year...
6. McClary, A.C, West, R.B, McClary, A.C, Pollack, J.R, Fischbein, N.J, Holsinger, C.F, Sunwoo, J, Colevas, A.D, Sirjani, D. Ameloblastoma: A Clinical Review and Trends in Management. European Archives of Oto-Rhino-Laryngology. 2015. Available at: http://med.stanford.edu/labs/vanderijn-west/docume...
7. Bachmann, A and Linfesty, R. Ameloblastoma, Solid/Multicystic Type. Head and Neck Pathology. 2009; 3(4): 307-309. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC281157...
8. Sweeney, R.T, McClary, A.C, Myers, B.Rm Biscocho, J, Neahring, L, Kwei, K.A, Qu, K, Gong, X, Ng, T, Jones, C.D, Varma, S, Odegaard, J.I, Sugiyama, Tm Koyota, S, Rubin, B.P, Trocell, M.L, Pelham, R.J, Zehnder, J.L, Beachy, P.A, Pollackm J.R and West, R.B. Identification of Recurrent SMO and BRAF Mutations in Ameloblastomas. Nature Genetics. 2014; 46(7): 722-725. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC44182...
9. Rakotoarison, R.A, Ratovondrainy, W, Randriamanantena, T, Rakoto, F. A. Neglected Ameloblastomas: A Case Report. Med Buccale Chri Buccale. 2012; 18: 161-165. Available at: http://www.mbcb-journal.org/articles/mbcb/pdf/2012...
10. Philipose, T.R, Somayaji, B.V, Pai, M.R, Monteiro, F, Bhagavath, P, Hegde, P, Raj, B, Shetty, S. Adamantinoma and Ameloblastoma: Histologic Homologues. Journal of Evolution of Medical and Dental Sciences. 2014; 3(39). Available at: http://jemds.com/latest-articles.php?at_id=5123
11. Ariji, Y, Morita, M, Katsumata, A, Sugita, Y, Naitoh, M, Goto, M, Izumi, M, Kise, Y, Shimozato, K, Kurita, K, Maeda, H, Ariji, E. Imaging Features Contributing to the Diagnosis of Ameloblastomas and Keratocystic Odontogenic Tumours: Logistic Regression Analysis. A Journal of Head and Neck Imaging: DentoMaxilloFacial Radiology. 2011; 40(3): 133-140. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC361145...
12. Madras, J and Lapointe, H. Keratocystic Odontogenic Tumour: Reclassification of the Odontogenic Keratocyst from Cyst to Tumour. Journal of Canadian Dental Association. 2008; 74(2): 165a-165h. Available at: https://www.cda-adc.ca/jcda/vol-74/issue-2/165.pdf
13. Khalili, M and Shakib, P.A. Ameloblastic Fibrosarcoma of the Upper Jaw: Report of a Rare Case with Long-Term Follow-Up. Dental Research Journal. 2013; 10(1): 112-115. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC371481...
14. Bi, R, Shen, L, Zhu, X, Xu, X. Malignant Ameloblastoma (Metastatic Ameloblastoma) in the Lung: 3 Cases of Misdiagnosis as Primary Lung Tumor with a Unique Growth Pattern. Diagnostic Pathology. 2015; 10: 123. Available at: http://diagnosticpathology.biomedcentral.com/artic...
Further Reading:
Avon, S.L, McComb, J, Clokie, C. AmeloblasticCarcinoma: Case Report and Literature Review. Journal of Canadian Dental Association. 2003; 69(9): 573-576. Available at: http://www.ncbi.nlm.nih.gov/pubmed/14653932
Shaikhi, K, Neiders, M, Chen, F, Aguirre, A. Morphological Variants of Ameloblastoma and Their Mimickers. North American Journal of Medical Science. 2012; 5(1): 20-28. Available at: http://www.najms.net/v05i01p020w/
Sharma, A, Shaikh, A.M, Deshmukh, S.V, Dabholkar, J.P. Radical Management of Giant Ameloblastomas: A Case Series. Indian Journal of Otalaryngology and Head and Neck Surgery. 2012;64(4):399-401. Available at: www.ncbi.nlm.nih.gov/pmc/articles/PMC3477424/
Weissman, J.L, Snyderman, C.H, Yousem, S. A, Curtin, H. D. Ameloblastoma of the Maxilla: CT and MR Appearance. American Journal of Neuroradiology. 1993; 14: 223-226. Available at: http://www.ajnr.org/content/14/1/223.abstract
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Version 2 produced September 2016
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