الفهرس 
REVIEW OF THE LITERATUREOnly 14 pages are availabe for public view
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Abstract
Odontogenic cysts account for most cysts of the jaws where they are the most common cause of
chronic swellings. Some odontogenic cysts are of particular interest due to their peculiar
clinical behaviour reflected by their aggressive potentiality and their greater tendency to recur.
Also, the rare but well-known tendency of the epithelial lining of odontogenic cysts for neoplastic
transformation has attracted more attention to this group of jaw lesions.
This work was designated to study the different types of odontogenic cysts as regards to their
clinical presentation and histopathological features. Also, an immunohistochemical study was
conducted to get more close to the role of bcl-2 oncoprotein in the behaviour of odontogenic cysts
and the neoplastic transformation of their linings.
The mechanism through which bcl-2 promotes tumorigenesis is unique. The gene expression confers
survival advarrtage to a variety of cell types by inhibiting apoptosis, which constitutes one of
the most common pathways of tumorigenesis.
Twenty-five (25) cases of different types of odontogenic cysts were included in the study.
Selection was done to include as many types of odontogenic cysts as possible. There were (8)
keratocysts, (5) dentigerous cysts, (4) inflammatory, (l) COC, (4) cystic ameloblastoma and (3)
cases of neoplasia arising in odontogenic cyst wall (one SCC and two central cystic mucoepidermoid
carcinomas).
All cases were clinically examined to obtain a complete history. Sections from each case were
prepared for both routine histopathological staining with H&E and immunohistochemical staining with
bcl-2.
The clinical examination revealed some interesting fmdings but was in the overall in agreement with
the literature. A case of non syndrome multiple keratocyst was included, in addition to an
unusual case of bilateral dentigerous cyst.
Histopathological examination of all cases was done..The most interesting finding was that two
cases of central cystic mucoepidermoid carcinoma, and one case of squamous cell carcinoma in
odontogenic cyst wall were diagnosed. The remaining cases did not display any unusual features
except for respiratory epithelium metaplasia in a part of an inflammatory cyst wall The cases of
cystic ameloblastoma included all the different histologic variants.
The results of bcl-2 immunostaining revealed different patterns of expression between the
different types of odontogenic cysts. In the common inflammatory cyst lining the
reaction was negative. In dentigerous cysts and in calcifying odontogenic cyst,
expression was moderate and even faint.. Bcl-2 was intensely expressed inalmost all the
epithelial layers of keratocysts, in areas of respiratory metaplasia in the inflammatory
cyst, in cystic ameloblastoma and central mucoepidermoid carcinoma. The case of squamous cell
carcinoma in cyst wall showed moderate expression in all layers of dysplastic epi.t:hfllium as
well as in malignant epithelial cells.