Ameloblastoma


Ameloblastoma

Description, Causes and Risk Factors:

Ameloblastoma is the most common borderline odontogenic tumor of epithelial tissue origin. It accounts for about 1% of all the cysts and tumors of the jaws and 18% of the various odontogenic neoplasms. According to some authors, it is the second most common odontogenic neoplasm, and only odontoma outnumbers it in frequency of occurrence and there are others who go even further by claiming that excluding odontoma, the incidence of ameloblastoma is at least equal to the incidence of all the other odontogenic neoplasms combined.

Ameloblastoma

Ameloblastoma occurs in men more often than it occurs in women. Though it can be diagnosed at any age, ameloblastoma is most often diagnosed in adults in their 40s or 50s.

Despite being benign, ameloblastoma can be very aggressive, growing into the jawbone and causing swelling and pain. Very rarely, ameloblastoma cells can spread to other areas of the body, such as the lymph nodes in the neck and the lungs.

Ameloblastoma is divided into 3 clinicoradiologic groups: Solid or multicystic, unicystic and peripheral. The solid ameloblastoma is the most common form of the lesion (86%). It has a tendency to be more aggressive than the other types and has a higher incidence of recurrence. Unicystic ameloblastoma has a large cystic cavity with luminal, intraluminal or mural proliferation of ameloblastic cells. It is a less aggressive variant and it has a low rate of recurrence, although lesions showing mural invasion are an exception and should be treated more agressively. Histologically, the peripheral ameloblastoma appears similar to the solid ameloblastoma. It is uncommon, usually presenting as a painless, non-ulcerated sessile or pedunculated gingival lesion on the alveolar ridge. Several histopathologic types of ameloblastoma are described in the literature, including those with plexiform, follicular, unicystic, basal cell, granular cell, clear cell, acanthamatous and desmoplastic patterns.

This neoplasm originates within the mandible or maxilla from epithelium that is involved in the formation of teeth. Potential epithelial sources include the enamel organ, odontogenic rests (rests of Malassez, rests of Serres), reduced enamel epithelium, and the epithelial lining of odontogenic cysts, especially dentigerous cysts. The trigger or stimulus for neoplastic transformation of these epithelial residues is totally unknown.

Mechanisms by which ameloblastomas gain a growth and invasion advantage include overexpression of anti-apoptotic proteins (Bcl-2, Bcl-xL) and interface proteins (fibroblast growth factor [FGF], matrix metalloproteinases [MMPs]). Ameloblastomas, however, have a low proliferation rate. Mutations of the p53 gene do not appear to play a role in the development or growth of ameloblastoma.

Symptoms:

Signs and symptoms:

    Occurs predominantly in the fourth and fifth decades of life.

  • Appears to be no gender predilection (slightly more in males).

  • Mandibular molar-ramus area is the most favored site, slowly growing, painless, hard bony swelling or expansion of jaw, thinning of cortical plates produces “egg shell crackling.”

  • Other symptoms - Tooth mobility, root resorption and paresthesia if inferior alveolar nerve is affected.

Diagnosis:

Ameloblastoma sometimes causes pain and swelling in the jaw, but often it causes no signs or symptoms. It may be discovered on a routine dental X-ray.To gather more information about the tumor and make a diagnosis, doctors may recommend tests and procedures such as:

Imaging tests. Imaging tests, such as X-ray, CT and MRI, help doctors determine the extent of an ameloblastoma.

Removing a sample of tissue for testing. A biopsy is done to remove a sample of tumor cells for laboratory analysis.

Histologically, most ameloblastomas have the follicular or plexiform pattern, although basaloid, granular cell or desmoplastic variations may also be seen. It is generally accepted that there is no relationship between the individual patterns and the behavior of the tumor or its prognosis. For this reason, pathologists may choose not to report the histologic pattern. (Histologic pattern is not to be confused with the designation of conventional, unicystic or peripheral types, as these descriptors have considerable impact on the patients' treatment and prognosis). The case presented showed features of both follicular and plexiform variants, possessing islands and anastomosing strands of odontogenic epithelium enmeshed in a fibrous stroma. These islands and strands contain basal cells that are columnar, hyperchromatic and lined up in a palisaded fashion at the periphery. The cells have vacuolated cytoplasm and the nuclei exhibit reverse polarization away from the connective tissue. The cells in the central portions of the epithelial islands are more loosely arranged, mimicking stellate reticulum. The lesion is cytologically bland with no pleomorphism or mitotic figures noted.

Treatment:

Treatment Options Include:

    Surgery to remove the tumor. The goal of surgery is to remove the tumor and a thin margin of healthy tissue that surrounds it. Ameloblastoma often grows into the nearby jawbone, so oral and maxillofacial surgeons remove the affected portion of this bone. An aggressive approach to surgery reduces the risk that ameloblastoma will recur.

  • Surgery to repair the jaw. If surgery involves removing a portion of your jawbone, reconstructive and plastic surgeons will repair the jaw. Surgeons work to restore your ability to eat and speak, as well as to improve the appearance of your jaw.

  • Radiation therapy. Radiation therapy may be recommended in certain situations, such as in the case of a large tumor or one that shows signs of cancer. Radiation therapy may reduce the risk of the tumor recurring. When a tumor can't be removed with surgery, radiation therapy may be the only treatment.

  • Supportive care. A variety of professionals will work with you to help you maintain your quality of life during and after treatment for ameloblastoma. At Mayo Clinic, these professionals may include dietitians, speech therapists, swallowing therapists, physical therapists, and specialists who make artificial replacements for missing teeth or other damaged natural structures in the mouth (prosthodontists).

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

Related disease: Benign cementoblastoma

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