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Ameloblastoma

What Is It, Causes, Signs and Symptoms, and More

Author:Anna Hernández, MD

Editors:Alyssa Haag,Ian Mannarino, MD, MBA,Kelsey LaFayette, DNP, ARNP, FNP-C

Illustrator:Jessica Reynolds, MS

Copyeditor:David G. Walker


What is an ameloblastoma?

An ameloblastoma is a rare odontogenic tumor, meaning it originates from the tissues responsible for the formation of the teeth. They are typically slow-growing lesions that have a high recurrence rate and the potential to spread to other parts of the body (e.g., lungs). According to the latest World Health Organization (WHO) Classification of Head and Neck Tumors, ameloblastomas are classified into four different types, including conventional ameloblastoma, previously solid/multicystic ameloblastoma; unicystic ameloblastoma; peripheral ameloblastoma; and metastasizing ameloblastoma. 

Tumor below the jaw.

What causes ameloblastomas?

The exact cause of ameloblastomas is not clearly understood; however, it is thought that ameloblastomas arise from immature tooth tissue that has not undergone differentiation. Recent evidence suggests their development is associated with the dysregulation of signaling pathways that are activated during usual tooth development, including the sonic hedgehog (SHH) and mitogen-activated protein kinase (MAPK) pathways. These pathways play a key role in structuring the general shape of the body by guiding how the various tissues differentiate during embryonic development. 

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What are the signs and symptoms of ameloblastomas?

Ameloblastomas generally present as a slow-growing, painless swelling of the jaw. The bone holding the bottom row of teeth is called the mandible, while the bone holding the top row of teeth is the maxilla. Most ameloblastoma cases occur in the mandible, predominantly in the third molar region, but they can also develop in the maxilla. Due to their aggressive nature, ameloblastomas can become large lesions causing facial disfigurement, dental malocclusion, and loosening of the teeth. Occasionally, the tissues near the jaw, including the sinuses and eye sockets, may become involved. Although pain is not a characteristic sign of ameloblastoma, it can occur if there is bleeding inside the tumor or in the surrounding tissues. 

While ameloblastomas can be locally aggressive, they rarely metastasize and spread to other parts of the body. If metastasis does occur, the main site is usually the lungs; however, regional lymph nodes may also be affected. 

How are ameloblastomas diagnosed?

Diagnosis of ameloblastoma is achieved through a combination of imaging techniques and a biopsy of the lesion. Occasionally, ameloblastoma is detected incidentally on dental X-rays (i.e., orthopantomogram). On radiographs, unicystic ameloblastoma appears as a lytic lesion with scalloped margins, signifying an area of bone destruction that caused a hole. On the other hand, conventional or multicystic ameloblastoma appears as the classic “soap bubble” appearance on an X-ray. In most cases, a CT scan or MRI of the jaw is performed to better characterize the lesion and determine the extent of bone and soft tissue involvement.

Although the radiologic characteristics can help raise suspicion of ameloblastoma, definitive diagnosis requires a biopsy of the lesion. Histopathology can help rule out various differential diagnoses of ameloblastoma, which includes bone disorders like ossifying fibroma, osteomyelitis, giant cell tumor, myeloma, and sarcoma. In cases of metastasizing ameloblastoma, a positron emission tomography (PET) scan may also be done to detect distant sites of metastasis. 

How are ameloblastomas treated?

Treatment of ameloblastoma involves radical maxillofacial surgery. For conventional ameloblastoma, current surgical treatment involves a complete “en bloc” resection, meaning a portion of the mandible or maxilla is surgically removed along with the tumor. A wide resection with a bony margin of 1 to 1.5 centimeters is typically recommended due to the high recurrence rate with conservative surgery. Following removal of the tumor, reconstruction of the mandible or maxilla is performed to help minimize any speech and swallowing difficulties that may arise after surgery.

In cases of metastasizing ameloblastoma, chemotherapy may be used in combination with surgery. Ameloblastomas that are positive for the BRAF V600 mutation may receive MAPK pathway targeted therapy with medications, such as dabrafenib or vemurafenib. 

The prognosis of ameloblastoma depends on the age of the individual, location and size of the tumor, and stage of disease. Although most ameloblastomas grow slowly over time, if left untreated, they can continue to grow and cause severe facial disfigurement as well as pose a risk to the airway. 

What are the most important facts to know about ameloblastomas?

Ameloblastoma is a rare, benign odontogenic tumor that arises in the jaw. They are slow-growing, locally aggressive lesions that have a high rate of recurrence. The most common clinical presentation is a painless swelling of the jaw; however, complications may include facial disfigurement, dental malocclusion, and loosening of the teeth due to the growth of the lesion. Diagnosis includes a CT scan or MRI of the jaw as well as a biopsy of the lesion. Treatment generally includes radical excisional surgery followed by reconstruction of the jaw. In cases of metastasizing ameloblastoma, chemotherapy or targeted molecular therapies, like dabrafenib or vemurafenib, may be used in conjunction with surgery. 

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Related links

Anatomy and physiology of the teeth
Development of the teeth
Hedgehog signaling pathway

Resources for research and reference

Chadwick JW, Ruo S, Ali Amir Khadivi, Cuddy K. Multidisciplinary management of an advanced mandibular ameloblastoma: etiopathogenesis, surgical management and prosthetic rehabilitation. Oral and Maxillofacial Surgery Cases. 2023;9(2):100296-100296. doi:https://doi.org/10.1016/j.omsc.2023.100296

‌Ebeling M, Scheurer M, Sakkas A, Pietzka S, Schramm A, Wilde F. BRAF inhibitors in BRAF V600E-mutated ameloblastoma: systematic review of rare cases in the literature. Medical Oncology. 2023;40(6). doi:https://doi.org/10.1007/s12032-023-01993-z

‌Effiom O, Ogundana O, Akinshipo A, Akintoye S. Ameloblastoma: current etiopathological concepts and management. Oral Diseases. 2017;24(3):307-316. doi:https://doi.org/10.1111/odi.12646

‌Ghai S. Ameloblastoma: an updated narrative review of an enigmatic tumor. Cureus. Published online August 6, 2022. doi:https://doi.org/10.7759/cureus.27734