Ameloblastoma (Ameloblastomas)

Ameloblastoma - high mag[1]

Ameloblastoma is a rare odontogenic and primarily benign tumor developing in the upper jaw or mandible. It is often diagnosed incidentally, as many patients are asymptomatic. However, aggressive growth and the potential for malignant transformation can induce symptoms, which should be evaluated through a detailed workup, with an emphasis on imaging studies such as computed tomography.

Presentation

Although they are considered to be one of the most common odontogenic tumors, ameloblastomas are a rare occurrence in clinical practice [1]. Their incidence is equal in both genders and may be diagnosed at any anytime between the first and sixth decade of life [1] [2] [3]. However, the majority of tumors are identified in the third and fourth decades of life, when a slow-growing painless mass is observed [1] [2] [3]. The mandible (the ramus and the angle) is the predominant site of ameloblastoma development, whereas the upper jaw (the canine or molar regions) is the second important location [1] [4]. Ameloblastomas, when asymptomatic and minimally aggressive, are frequently associated with an unerupted third molar [5], but when the tumor exhibits more severe proliferation and extends into adjacent tissues, various symptoms may appear. Facial swelling and/or asymmetry, pain, displacement and loosening of the teeth, mucosal ulceration (due to the protraction of the tumor), as well as ill-fitting dentures, obstruction of the nasal passage and even fractures of the surrounding bones are documented presentations of ameloblastoma [1] [2] [3] [5] [6]. In approximately 2% of cases, the tumor undergoes malignant transformation and metastatic dissemination can pose a significant and even life-threatening risk for the patient [3] [7]. For this reason, an early diagnosis not only carries a less aggressive approach to therapy but also minimizes the chances of an adverse outcome. More importantly, some forms of ameloblastoma can recur after therapy, and even metastasize, thus strengthening the role of long-term patient follow-up [1] [2].

Workup

Any facial symptoms must be taken seriously, but in order to obtain a complete view of their onset and progress, a detailed patient history should be the first step during workup. Furthermore, a meticulous physical examination focused on the oral cavity and a full ear nose and throat (ENT) exam can confirm some of the possible symptoms of ameloblastoma and detect a mass in the mandible or the upper jaw. In that case, imaging studies, the gold standard when it comes to evaluating a mass in the oral cavity, must be employed. Based on the appearance of the tumor on radiography, computed tomography (CT), or magnetic resonance imaging (MRI), four clinical types are described in the literature [1] [2] [3] [7] [8]:

  • Unicystic - Described as the mildest form of ameloblastoma and responsible for about 6% of cases, this type is demarcated by an intraluminal or intramural proliferation of a well-circumscribed radiolucency shown on X-rays or CT [1] [5].
  • Multicystic (or solid) - Accounting for more than 85% of all ameloblastomas, multicystic lesions infiltrate the surrounding tissues and cause the destruction of bone and adjacent soft tissues. On X-rays and CT, an expansive multiloculated radiolucent lesion is seen, and the term "soap bubble-like" appearance is mentioned in some reports [2]. Erosion or unerupted tooth displacement can be observed in this type as well [2].
  • Peripheral - Tumor confinement to the gingival or alveolar mucosa is the defining criteria for a peripheral ameloblastoma, which does not invade the underlying bone [2]. Hence, radiography shows absence of skeletal infiltration, but rare cases of metastatic spread with peripheral forms have been described [2].
  • Malignant - In very rare cases, ameloblastomas become malignant tumors (or arise de novo as primary malignant lesions) [7].
  • Desmoplastic ameloblastoma (DA) is another variant of this tumor, distinguished by its development in the anterior jaw and a mixed radiolucent-radioopaque appearance [2] [8].

To make a final diagnosis, a biopsy of the lesion (often performed after surgical removal of the tumor) and subsequent histopathological examination is necessary. On the basis of histological features, ameloblastomas are subdivided into follicular, plexiform, granular and acanthomatous types [2].

Treatment

Prognosis

Etiology

Epidemiology

Sex distribution
Age distribution

Pathophysiology

Prevention

Summary

Patient Information

Self-assessment

References

  1. Dandriyal R, Gupta A, Pant S, Baweja HH. Surgical management of ameloblastoma: Conservative or radical approach. Natl J Maxillofac Surg. 2011;2(1):22-27.
  2. Masthan KMK, Anitha N, Krupaa J, Manikkam S. Ameloblastoma. J Pharm Bioallied Sci. 2015;7(1):S167-S170.
  3. Mendenhall WM, Werning JW, Fernandes R, Malyapa RS, Mendenhall NP. Ameloblastoma. Am J Clin Oncol. 2007;30(6):645-648.
  4. Suma MS, Sundaresh KJ, Shruthy R, Mallikarjuna R. Ameloblastoma: an aggressive lesion of the mandible. BMJ Case Rep. 2013;2013:bcr2013200483.
  5. Ramesh RS, Manjunath S, Ustad TH, Pais S, Shivakumar K. Unicystic ameloblastoma of the mandible - an unusual case report and review of literature. Head Neck Oncol. 2010;2:1.
  6. Ariji Y, Morita M, Katsumata A, et al. Imaging features contributing to the diagnosis of ameloblastomas and keratocystic odontogenic tumours: logistic regression analysis. Dentomaxillofacial Radiology. 2011;40(3):133-140.
  7. Rizzitelli A, Smoll NR, Chae MP, Rozen WM, Hunter-Smith DJ. Incidence and Overall Survival of Malignant Ameloblastoma. Chuu C-P, ed. PLoS ONE. 2015;10(2):e0117789.
  8. Sharma Lamichhane N, Liu Q, Sun H, Zhang W. A case report on desmoplastic ameloblastoma of anterior mandible. BMC Res Notes. 2016;9:171.



Media References

  1. Ameloblastoma - high mag, CC BY-SA 3.0

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