Ameloblastoma classification: Difference between revisions
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*Malignant | *Malignant | ||
**The malignant ameloblastoma is a rare entity. It is defined as an ameloblastoma that has already metastasized but still maintains its classical microscopic features. | **The malignant ameloblastoma is a rare entity. It is defined as an ameloblastoma that has already metastasized but still maintains its classical microscopic features. | ||
The solid ameloblastoma is the most common form of the lesion | The WHO classification of odontogenous tumors (2005) currently defines malignant ameloblastoma (MA) as “an ameloblastoma that metastasizes in spite of a benign histological appearance.” Ameloblastoma with cytological atypia is defined as ameloblastic carcinoma even if metastasis is absent. Thus, MA is defined as a retrospective diagnosis that can only be made when metastasis occurs. In many cases, MA not only maintains the histological characteristics of the parent tumor but also continues to display similarly indolent clinical behavior. However, the histological features of MA of the lung are seldom discussed in the literature. Because of the low frequency of MA and its unclear clinical history, physicians should avoid misdiagnosing MA as other primary or metastatic tumors of the lung. | ||
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 | (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 | 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 |
Revision as of 09:26, 25 December 2015
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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 may be classified based on histopathology into six subtypes: follicular, plexiform, acanthomatous, basal cell, granular cell, and desmoplastic. Based on the location, ameloblastoma may be classified into either intra-osseous or extra-osseous.
Classification
Based on the location, ameloblastoma may be classified into the following two subtypes:
- Intra-osseous.
- Intraosseous ameloblastoma is locally aggressive.
- Intraosseous ameloblastoma may include the subtypes such as follicular, plexiform, acanthomatous, unicystic, granular cell, basal cell, or desmoplastic
- Extra-osseous
- Extraosseous ameloblastoma may include the subtypes such as follicular, plexiform, or basal cell
- Extraosseous ameloblastoma is benign
- Extraosseous ameloblastoma is also known as peripheral ameloblastoma
Based on histology, intraosseous ameloblastoma may be subclassified into two groups which includes the following:
- Solid/multicystic
- More commonly reoccur
- Unicystic.
- Unlikely to reoccur.
- Classically found in younger individuals.
Ameloblastoma is divided into three clinicoradiologic groups:
- Solid or multicystic
- Solid ameloblastoma is the most common form of the lesion. Approximately 86% of the ameloblastomas are solid. It has a tendency to be more aggressive than the other types and has a incidence of recurrence. Multicystic ameloblastoma can infiltrate into the adjacent tissue and has the ability to recur and even metastasize. Its prevalence is a slightly older age group than the unicystic ameloblastoma. Radiographically, the appearance is generally unilocular or multilocular.
- Unicystic
- 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. The unicystic ameloblastoma usually appears as a “cystic” lesion with either an intraluminal or an intramural proliferation of the cystic lining.[7] Radiographically, it may resemble a well-circumscribed slow-growing radiolucency.
- Peripheral.
- 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. Peripheral ameloblastoma mostly appears in the alveolar mucosa. It is a soft-tissue version of an ameloblastoma but can also involve the underlying bone.
- Malignant
- The malignant ameloblastoma is a rare entity. It is defined as an ameloblastoma that has already metastasized but still maintains its classical microscopic features.
The WHO classification of odontogenous tumors (2005) currently defines malignant ameloblastoma (MA) as “an ameloblastoma that metastasizes in spite of a benign histological appearance.” Ameloblastoma with cytological atypia is defined as ameloblastic carcinoma even if metastasis is absent. Thus, MA is defined as a retrospective diagnosis that can only be made when metastasis occurs. In many cases, MA not only maintains the histological characteristics of the parent tumor but also continues to display similarly indolent clinical behavior. However, the histological features of MA of the lung are seldom discussed in the literature. Because of the low frequency of MA and its unclear clinical history, physicians should avoid misdiagnosing MA as other primary or metastatic tumors of the lung.
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
Ameloblastoma is a true neoplasm of enamel organ type. Robinson described it as unicentric, nonfunctional, intermittent in growth, anatomically benign, and clinically persistent. It is the second most common odontogenic neoplasm. Histologically it is of six subtypes: follicular, plexiform, acanthomatous, granular, desmoplastic, and basilar. It affects mandible more than maxilla especially in the region of molar-ramus area. It causes a slow growing, painless expansion of jaw which causes thinning of cortical plates. Root resorption, tooth mobility, and paresthesia are features seen in advanced cases of ameloblastoma. Radiographically it can be unicystic, multicystic, or solid and peripheral type. Multicystic or solid type is prevalent in 86% of cases. Unicystic ameloblastoma is of three subtypes: luminal, intraluminal, and mural
Clinically, ameloblastomas can be classified into 4 groups: unicystic, solid or multicystic, peripheral, and malignant. The unicystic ameloblastoma usually appears as a “cystic” lesion with either an intraluminal or an intramural proliferation of the cystic lining.[7] Radiographically, it may resemble a well-circumscribed slow-growing radiolucency. Multicystic ameloblastoma can infiltrate into the adjacent tissue and has the ability to recur and even metastasize. Its prevalence is a slightly older age group than the unicystic ameloblastoma. Radiographically, the appearance is generally unilocular or multilocular.[8] Peripheral ameloblastoma mostly appears in the alveolar mucosa. It is a soft-tissue version of an ameloblastoma but can also involve the underlying bone.[9] The malignant ameloblastoma is a rare entity. It is defined as an ameloblastoma that has already metastasized but still maintains its classical microscopic features.[10]
A histological classification subdivides into follicular, plexiform, acanthomatous and granular ameloblastoma. 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. Histologically it is of six subtypes: follicular, plexiform, acanthomatous, granular, desmoplastic, and basilar.
The following six histopathologic subtypes have been identified for ameloblastoma:
- Follicular
- Plexiform
- Acanthomatous
- Granular cell
- Basal cell
- Desmoplastic
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