What Is Ameloblastoma?
Ameloblastoma, a rare benign (noncancerous) growth or tumor, most commonly develops in the lower jaw near the molars or wisdom teeth. It is a type of odontogenic tumor. Odontogenic tumors are unique to dentistry as they arise from tissues that make our teeth. Ameloblastomas originate from the cells that form tooth enamel, which is the hard outer layer of the teeth. This tumor usually gets diagnosed between 40 to 60 years of age but can be diagnosed at any age. Ameloblastomas are usually not malignant; that is, they do not spread to other areas, but they are very aggressive and grow into the jawbone, resulting in pain and swelling. Sometimes, they can involve the sinuses and eye sockets. In rare cases, cells from ameloblastoma can spread to other parts of the body like the lymph nodes present in the neck and lungs. Ameloblastoma is also called adamantinoma or multilocular cysts.
What Are the Types of Ameloblastoma?
The WHO (World Health Organization) classified ameloblastoma into the following four types in 2017:
Conventional or Solid or Multicystic Ameloblastoma - Radiographically, multiple large cystic areas can be seen in this type. It is slow-growing and locally aggressive. Multicystic or conventional ameloblastoma accounts for almost 85 % of all ameloblastomas.
Unicystic Ameloblastoma - Around 10 % of ameloblastoma cases are this type, and commonly affects younger individuals (20 to 30 years old). Here, only a single cyst cavity is seen, often near the unerupted wisdom teeth.
Peripheral or Extraosseous Ameloblastoma - This type comprises around 2 to 10 % of all ameloblastomas. Peripheral ameloblastoma (PA) is usually confined to the gingival or alveolar mucosa and does not involve the underlying bone.
Malignant Ameloblastoma - Metastatic or malignant ameloblastoma appears benign histopathologically but rarely can lead to metastasis (mostly in the lungs).
What Causes Ameloblastoma?
Ameloblastomas originate in the cells that form the enamel (the protective lining of the teeth). Doctors do not know what exactly causes ameloblastoma. Injury to the jaw or mouth, gum or tooth infections, or tooth or gum inflammation (due to poor oral hygiene) are believed to trigger it. Other factors that can result in the formation of ameloblastoma are viral infections and a diet lacking essential minerals and protein. Scientists are not sure if these factors cause ameloblastomas, and the reason for some turning malignant is also not known.
Recent research has shown a relationship between mutations of certain genes that control cell growth and division and the formation of ameloblastoma. BRAF and SMO gene mutations have been seen in almost 80% of all ameloblastoma patients.
Who Is at Risk of Developing Ameloblastoma?
After odontoma, ameloblastoma is the second most common odontogenic tumor (almost one-third of all cases) and the most common lucent lesion (lesions that appear darker on an X-ray). They are usually slow-growing and affect men and women equally in the fourth to sixth decades of life (mean age being 39 years). Ameloblastomas are sometimes associated with basal cell nevus syndrome (an inherited condition that causes abnormal facial characteristics) and Gardner syndrome (an inherited condition characterized by gastrointestinal polyps, multiple osteomas, and skin or soft tissue tumors).
What Are the Symptoms of Ameloblastoma?
Ameloblastomas are usually painless and hard growths seen near the angle of the mandible, near the wisdom tooth or third molar. They can also develop anywhere in the lower jaw (80 %) and upper jaw (20 %). When it occurs in the upper jaw, it is commonly seen near the premolar region and can extend to the maxillary sinus.
As the lesion usually grows slowly over several months or years, the only symptom most people have for a while is swelling in the back of the mandible (lower jaw). The lesions in such individuals are usually seen when the dentist advises getting an X-ray for some other reason. Some people might experience jaw and tooth pain. In some cases, ameloblastomas grow fast and are painful. They can result in tooth displacement, numbness, bone pain, mobile teeth, difficulty speaking, mouth ulcerations, and can spread to the eye socket, nose, or skull. Rarely, the lesion grows so big that the airway gets blocked, and mouth opening and closing are affected.
It is crucial to diagnose ameloblastoma early and treat it promptly to stop its growth and possible metastasis. Though not reported very often, ameloblastomas can become malignant and spread to other areas of the body. Recurrence, which is seen in rare cases, might be fatal.
How Is Ameloblastoma Diagnosed?
Ameloblastomas are usually diagnosed accidentally during dental X-rays, where they appear as soap bubbles on the film. If the patient complains of swelling or jaw pain with mobile teeth, the following tests can be used to diagnose:
Imaging tests - X-ray, CT (computed tomography) scan, and MRI (magnetic resonance imaging) scan can help determine the tumor's extent.
Biopsy - To confirm ameloblastoma, the dentist might send a sample of tissue or cells to a lab for testing. The doctor might collect the sample using a needle or by making a small cut.
Differential Diagnosis:
The symptoms due to the following disorders can be similar to ameloblastoma:
Hard Odontoma - It is a benign dental tumor that is composed of irregularly placed normal dental tissues.
Osteosarcoma - It is a type of bone cancer that originates in the bone-forming cells.
Globulomaxillary Cyst - It is a fluid or pus-filled lesion seen between the maxillary lateral incisor and canine.
How Is Ameloblastoma Treated?
Chemotherapy and radiation therapy do not shrink noncancerous ameloblastomas. So, surgery is the treatment of choice. Surgery is done to remove the tumor. To avoid tumor cells from growing back, the surgeon will resect some healthy tissue surrounding the tumor. Sometimes, a part of the jaw might also be removed along with some arteries and nerves. The surgeon needs to be aggressive to reduce the risk of recurrence.
After the surgery, the patient will need another surgery to repair the jaw. The surgeon will reconstruct the jaw using artificial bone or bone from some other place in the body to improve the structure of the jaw and help in speech and mastication.
As ameloblastomas can recur in a few cases, the patient will have to get a CT scan every year for the next 5 years or more. In case the tumor is back, it is commonly found to be malignant. If that is the case, then radiation therapy is recommended to stop or slow the growth. If surgery is not possible, then radiation therapy using high-powered energy beams and supportive care are given. Mortality due to ameloblastoma is rare.
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