Ameloblastoma overview

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Overview

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Classification

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Differentiating Ameloblastoma from other Diseases

Epidemiology and Demographics

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]

Overview

Ameloblastoma is a rare, benign tumor of odontogenic epithelium much more commonly appearing in the mandible than the maxilla. While these tumors are rarely malignant or metastatic (that is, they rarely spread to other parts of the body), and progress slowly, the resulting lesions can cause severe abnormalities of the face and jaw. Odontogenic tumors comprise of a complex group of lesions of diverse histopathological types and clinical behavior. Of all swellings of the oral cavity, 9% are odontogenic tumors and within this group, ameloblastoma accounts for 1% of lesions. WHO defines it as a locally invasive polymorphic neoplasia that often has a follicular or plexiform pattern in a fibrous stroma. Its behavior has been described as being benign but locally aggressive. In 20% of all cases the tumor can be found in the `maxilla, predominantly in the canine or molar region. Within the mandible, 70% are located in the molar region or the ascending ramus, 20% in the premolar region and 10% in the anterior part. Ameloblastoma was first described in 1868 by Broca. Based on the location, ameloblastoma may be classified into either intra-osseous or extra-osseous. Based on the clinicoradiologic features, ameloblastoma may be classified into four groups: solid or multicystic, unicystic, peripheral, and malignant. On gross pathology, the characteristic findings of ameloblastoma may include solid and cystic, mulitcystic and intraosseous or extraosseous, or rarely unicystic. On microscopic histopathological analysis, stellate reticulum, giant cells, subepithelial hyalinization, and columnar basal cells in palisading arrangement with vacuolated cytoplasm are characteristic findings of ameloblastoma. The exact pathophysiology of ameloblastoma is not fully understood. It is thought that ameloblastoma is the result of either suppression of matrix metalloproteinase-2 that may inhibit the local invasiveness of ameloblastoma, or there is also some research suggesting that α5β1 integrin may participate in the local invasiveness of ameloblastomas. Genes involved in the pathogenesis of ameloblastoma include BRAF V600E. There are no established causes for ameloblastoma. It is thought that ameloblastoma is the result of either suppression of matrix metalloproteinase-2 that may inhibit the local invasiveness of ameloblastoma, or there is also some research suggesting that α5β1 integrin may participate in the local invasiveness of ameloblastomas. Genes involved in the pathogenesis of ameloblastoma include BRAF V600E. The incidence of ameloblastoma is approximately 1.96, 1.20, 0.18, and 0.44 per 100,000 for black males, black females, white males, and white females respectively worldwide. Ameloblastoma affects men and women equally. There is no racial predilection to the ameloblastoma. Ameloblastoma usually occur in middle age group i.e. 20-40 years: the median age at diagnosis is 39 years. The incidence of ameloblastoma is approximately 1.96, 1.20, 0.18, and 0.44 per 100,000 for black males, black females, white males, and white females respectively worldwide. Ameloblastoma affects men and women equally. There is no racial predilection to the ameloblastoma. Ameloblastoma usually occur in middle age group i.e. 20-40 years: the median age at diagnosis is 39 years. Symptoms of ameloblastoma include mouth sores, painless swelling, loose teeth, facial deformity, swelling and numbness of the jaw, pain surrounding the teeth or jaw, and pain associated with the tissue growth, if ameloblastoma spreads to the sinus cavities and floor of the nose. The mainstay of therapy for ameloblastoma is surgery. Adjunctive chemotherapy/radiation/chemoradiation may be required.

Historical Perspective

Ameloblastoma was first described by Broca. This type of odontogenic neoplasm was designated as an adamantinoma by the French physician Louis-Charles Malassez.

Classification

Ameloblastoma may be classified based on histopathology into six subtypes including follicular, plexiform, acanthomatous, basal cell, granular cell, and desmoplastic. Based on the location, ameloblastoma may be divided into either intra-osseous or extra-osseous. Based on the radiologic features, ameloblastoma may be classified into four groups including solid or multicystic, unicystic, peripheral, and malignant.

Pathophysiology

Ameloblastoma arise from remnants of ameloblast or dental lamina, dentigerous cysts, or basal layer of oral mucosa. There is evidence that suppression of matrix metalloproteinase-2 may inhibit the local invasiveness of ameloblastoma. On gross pathology, the characteristic findings of ameloblastoma may include solid and cystic, multicystic and intraosseous or extraosseous, or rarely unicystic. On microscopic histopathological analysis, stellate reticulum, giant cells, subepithelial hyalinization, and columnar basal cells in palisading arrangement with vacuolated cytoplasm are characteristic findings of ameloblastoma. The exact pathophysiology of ameloblastoma is not fully understood. It is thought that ameloblastoma is the result of either suppression of matrix metalloproteinase-2 that may inhibit the local invasiveness of ameloblastoma, or there is also some research suggesting that α5β1 integrin may participate in the local invasiveness of ameloblastoma. Genes involved in the pathogenesis of ameloblastoma include BRAF V600E

Causes

There are no established causes for ameloblastoma. It is thought that ameloblastoma may be the result of either decreased expression of matrix metalloproteinase-2 which helps in inhibition of the local invasiveness of ameloblastoma, or it is may be due to increased expression of α5β1 integrin which participate in the local invasiveness of ameloblastoma.

Differential Diagnosis

Ameloblastoma must be differentiated from other diseases that cause symptoms similar to those of ameloblastoma, such as dentigerous cyst, odontogenic keratocyst, odontogenic myxoma, aneurysmal bone cyst, fibrous dysplasia, hard odontoma, osteosarcoma, and globulomaxillary cysts

Epidemiology and Demographics

The incidence of ameloblastoma is approximately 1.96, 1.20, 0.18, and 0.44 per 100,000 for black males, black females, white males, and white females respectively, worldwide. Ameloblastoma affects men and women equally. There is no racial predilection to the ameloblastoma. Ameloblastoma usually occur in middle age group i.e. 20-40 years; the median age at diagnosis is 39 years  

Risk Factors

There are no established risk factors for ameloblastoma. It is thought that common risk factors in the development of ameloblastoma may be dentigerous cyst, impacted teeth, injury to the mouth or jaw, infections of the teeth or gums, inflammation of the teeth or gums, infections by viruses, and lack of protein or minerals in the person's diet, and Gorlin-Goltz syndrome.

Screening

According to the United States Preventive Services Task Force, screening for ameloblastoma is not recommended.

Natural History, Complications and Prognosis

In several cases, the patients with ameloblastoma are asymptomatic. Depending on the extent of the tumor at the time of diagnosis, the prognosis may vary.

History and Symptoms

Symptoms of ameloblastoma include mouth sores, painless swelling, loose teeth, facial deformity, swelling and numbness of the jaw, pain surrounding the teeth or jaw, and pain associated with the tissue growth, if ameloblastoma spreads to the sinus cavities and floor of the nasal cavity.  

Physical Examination

Patients with ameloblastoma usually appear normal and clinical presentation of an ameloblastoma is usually limited. Common physical examination findings of ameloblastoma include facial asymmetry, swelling, and hemorrhage.

Laboratory Findings

There are no diagnostic lab findings associated with ameloblastoma.

Electrocardiogram

There are no ECG findings associated with amelobastoma.

Head X Ray

A head x-ray may be helpful in the diagnosis of ameloblastoma. Findings on an x-ray suggestive of ameloblastoma include polycystic, honeycombed mass arising within the alveolar border of the jaw.

CT

Head CT scan may be helpful in the diagnosis of ameloblastoma. Findings on CT scan suggestive of ameloblastoma include multiloculated, soap-bubble" lesion, erosion of the adjacent tooth roots and well demarcated borders with no matrix calcification.

MRI

Head and neck MRI may be helpful in the diagnosis of ameloblastoma. Findings on MRI diagnostic of ameloblastoma include mixed solid and cystic pattern, thick irregular walls with papillary solid structures projecting into the lesion.

Ultrasound

Ultrasound may be helpful in the diagnosis of ameloblastoma. Findings on an ultrasound suggestive of ameloblastoma include cystic mass with solid contents, flow signals, multilocular and honeycomb appearance.

Other Imaging Findings

There are no other imaging findings findings associated with acoustic neuroma.

Other Diagnostic Studies

Other diagnostic studies for ameloblastoma include incisional biopsy. Incisional biopsy is diagnostic of ameloblastoma.

Medical Therapy

The mainstay of therapy for ameloblastoma is surgery. Adjunctive chemotherapy/radiation/chemoradiation may be required.

Surgery

The mainstay of therapy for ameloblastoma is surgery. The predominant therapy for ameloblastoma is surgical resection. Adjunctive chemotherapy/radiation/chemoradiation may be required.

Primary Prevention

There are no primary preventive measures available for ameloblastoma.

Secondary Prevention

Secondary prevention strategies following ameloblastoma include follow-up examination at regular intervals for at least 10 years.

References


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