Ameloblastoma overview
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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 (the cells that create the enamel, or outside portion, of the teeth during development) 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. Additionally, because abnormal cell growth easily infiltrates and destroys surrounding bony tissues, wide surgical excision is required to treat this disorder. Further, dentists caution that wide surgical excision is not invasive enough to adequately treat this disorder. 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 upper jaw, 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. Ameloblastomas occur with equal frequency in both sexes. An Ameloblastoma is a rare tumor involving excess tissue growths around the jaw. It can occur either in the lower jaw or upper jaw bones. Commonly, the tumor occurs near the un-erupted teeth of the molars. Statistically, only 1% of all jaw tumors are Ameloblastomas and in most cases the growth is usually benign (non-cancerous) and non-metastatic (they do not spread). However, these tumors may be locally very aggressive, causing bone destruction at the tumor site. The abnormal growths are formed from cell parts that in normal cases would have turned into tooth enamel. If the condition is severe, then the tissue growth may even cause facial deformity. A diagnosis of Ameloblastoma is made through radiology imaging and biopsy of the tumor Generally, a surgical removal of the tumor is the preferred treatment method; though, recurrence of Ameloblastoma after surgery is a possibility
Historical Perspective
Ameloblastoma was first described in 1868 by Broca.[1][2]
Classification
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.[3][4][5][6][7]
Pathophysiology
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.[8][7]
Causes
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.[8]
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, osteosaarcoma, and globulomaxillary cysts.[9]
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. [8][5]
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 persons diet, and Gorlin-Goltz syndrome.
Screening
According to the United States Preventive Services Task Force, screening for ameloblastoma is not recommended. [10]
Natural History, Complications and Prognosis
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 nose.
Physical Examination
Laboratory Findings
Head X Ray
CT
On head and neck CT, ameloblastoma is characterized by multiloculated, expansile "soap-bubble" lesion, with well demarcated borders, no matrix calcification, and occasionally erosion of the adjacent tooth roots.[9]
MRI
Head and neck MRI scan may be diagnostic of ameloblastoma. Findings on MRI suggestive of ameloblastoma include mixed solid and cystic pattern, with thick irregular wall, often with papillary solid structures projecting into the lesion.[9]
Other Imaging Findings
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.[8]
Surgery
The mainstay of therapy for ameloblastoma is surgery. The predominant therapy for ameloblastoma is surgical resection. Adjunctive chemotherapy/radiation/chemoradiation may be required.[8]
Primary Prevention
Secondary Prevention
References
- ↑ Goldwyn, Robert; Constable, John; Murray, Joseph E. (1963). "Ameloblastoma of the Jaw". New England Journal of Medicine. 269 (3): 126–129. doi:10.1056/NEJM196307182690303. ISSN 0028-4793.
- ↑ Pandya NJ, Stuteville OH (1972). "Treatment of ameloblastoma". Plast Reconstr Surg. 50 (3): 242–8. PMID 4115148.
- ↑ Singh M, Shah A, Bhattacharya A, Raman R, Ranganatha N, Prakash P (2014). "Treatment algorithm for ameloblastoma". Case Rep Dent. 2014: 121032. doi:10.1155/2014/121032. PMC 4274852. PMID 25548685.
- ↑ Gümgüm S, Hoşgören B (2005). "Clinical and radiologic behaviour of ameloblastoma in 4 cases". J Can Dent Assoc. 71 (7): 481–4. PMID 16026635.
- ↑ 5.0 5.1 Toledo-Pereyra LH, Bergren CT (1987). "Liver preservation techniques for transplantation". Artif Organs. 11 (3): 214–23. PMID 3304226.
- ↑ Poser CM (1973). "Demyelination in the central nervous system in chronic alcoholism: central pontine myelinolysis and Marchiafava-Bignami's disease". Ann N Y Acad Sci. 215: 373–81. PMID 4513681.
- ↑ 7.0 7.1 Ameloblastoma. Libre pathology(2015) http://librepathology.org/wiki/index.php/Ameloblastoma Accessed on December 25, 2015
- ↑ 8.0 8.1 8.2 8.3 8.4 Ameloblastoma. Wikipedia(2015) https://en.wikipedia.org/wiki/Ameloblastoma Accessed on December 25, 2015
- ↑ 9.0 9.1 9.2 Salivary gland tumors. Radiopedia(2015) http://radiopaedia.org/articles/ameloblastoma Accessed on December 26, 2015
- ↑ http://www.uspreventiveservicestaskforce.org/BrowseRec/Search?s=ameloblastoma Accessed on December 28, 2015.