COM March 2018 Diagnosis

Large multilocular, expansile radiolucency, right posterior mandible

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This is a 20-year-old white male who was referred by his general dentist for a large swelling on the right mandible.

Case of the Month Summary

Aneurysmal bone cyst (ABC)

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The site being posterior mandible, the obvious expansion of the jaw, the multilocular radiolucency and the age of the patient are all supportive of the diagnosis of aneurysmal bone cyst which should be left high on the list of differential diagnosis given the young age of this patient. The histology however, is not supportive of ABC.

Aneurysmal bone cyst is a disease of the young, usually occurs before the age 20. There is a slight predilection for females and is more common in the posterior mandible. Clinical Features include pain and swelling. Radiographically, ABC presents as multilocular or honeycombed expansile radiolucency with thinning leading to ballooning or ‘blow out’ distention of bone which is highly suggestive of ABC.

Solid ameloblastoma

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The location being posterior mandible, the expansion, the multilocular radiolucency are all typical of solid ameloblastoma. The age of this patient however is young for solid ameloblastoma. The histology is not that of solid ameloblastoma.

Solid ameloblastoma is one of the most common benign neoplasms of odontogenic origin. It is benign but locally aggressive; it is slow-growing and persistent. It affects a wide range of age distribution but is mostly a disease of adults, at an average age of 33, with equal sex distribution. About 85% of ameloblastomas occur in the posterior mandible; most of these occur in the molar-ramus area, and some occur in the anterior mandible. About 15% occur in the maxilla, the vast majority of these in the posterior maxilla, in patients around the age of 60 and tend to have a worse prognosis than those of the mandible. Solid ameloblastomas in general are characteristically expansile, radiolucent and multilocular in nature. They can move teeth apart and resorb teeth. They can perforate bone.

Odontogenic myxoma

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The site being posterior mandible, the obvious expansion of the jaw and the multilocular radiolucency are all supportive of the diagnosis of odontogenic myxoma. The age of the patient especially that the lesion started as young as 18 years of age is on the young age range of odontogenic myxoma. The histology is that of odontogenic myxoma.

Odontogenic myxoma is not common; it usually occurs in jaw bones, in the tooth-bearing areas of the jaw. It is benign, but locally aggressive neoplasm. It has the potential for extensive bony destruction and extension into the surrounding structures.. Almost 75% of odontogenic myxomas occur in patients around 23-30 years of age with a slight female predilection (1:1.5 male-to-female ratio). It rarely occurs in patients over 50 or under 10 years of age. It occurs almost equally in the maxilla and mandible with a slight predilection for the posterior mandible. A few cases are described in the ramus and condyle, non-tooth bearing areas. Odontogenic myxoma is slow-growing, persistent and destructive. Most cases are expansile and can displace and resorb teeth. In the maxilla, they usually invade the maxillary sinuses and, in rare cases, cross the midline to the opposing sinus. Radiographically, the majority present as expansile and multilocular, though some are unilocular with or without scalloped borders, and rare cases present with a diffuse and mottled appearance which can be mistaken for a malignant neoplasm.

Central giant cell granuloma (CGCG)

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The multilocular and expansile radiolucency is supportive of the diagnosis of CGCG. The age is also consistent with this condition but not the gender and the site being so posterior mandible. Since CGCG present anterior to the first molar pushing anteriorly rather than posteriorly. The histology is not supportive of CGCG.

Central giant cell granuloma is a non-neoplastic process that can occasionally behave in a very aggressive and expansile manner, destroying bone and displacing teeth. Over 60% of CGCG cases occur in patients younger than 30 years of age, with twice as many occurrences in females as in males. Over 70% of cases occur in the mandible anterior to the first molar tooth.

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