Diagnostic dilemma of unicystic ameloblastoma: novel parameters to differentiate unicystic ameloblastoma from common odontogenic cysts.

Diagnostic criteria that have been specified for unicystic ameloblastomas (UAs) are not always helpful to differentiate these cystic tumors from common odontogenic cysts. The aim of this study therefore was to identify additional histopathological features (other than the features considered for the diagnosis of UA at present) that would be helpful to differentiate UA from odontogenic cysts. One hundred histopathologically confirmed unicystic ameloblastomas and 20 cases each of radicular, inflamed dentigerous and non-inflamed dentigerous cysts were selected. Histopathological features of the UAs that are not used as diagnostic criteria at present were identified. Hyperplastic arcading epithelial proliferations with stellate-reticulum-like and vacuolated cells were always seen associated with inflammation in odontogenic cysts, while in UA plexiform-like areas were also seen without inflammation (P < 0.001). In addition, a spiky rete pattern was observed in non-inflamed UA while this pattern was observed only in inflamed odontogenic cysts. Furthermore, spiky retes together with subepithelial hyalinization were usually observed in UAs while only subepithelial hyalinization was observed in non-inflamed dentigerous cysts. Combinations of histopathological features were identified to differentiate non-inflamed UA from common odontogenic cysts. However, presence of inflammatory changes in UA precludes the use of features identified in the present study for diagnostic purposes.

Gunawardhana KS ，Jayasooriya PR ，Tilakaratne WM 《-》

BRAFV600E mutation in the diagnosis of unicystic ameloblastoma.

Unicystic ameloblastoma, an odontogenic neoplasm, presents clinical and radiographic similarities with dentigerous and radicular cysts, non-neoplastic lesions. It is not always possible to reach a final diagnosis with the incisional biopsy, leading to inappropriate treatment. The BRAFV600E activating mutation has been reported in a high proportion of ameloblastomas. The purpose of the study was to assess the utility of the detection of the BRAFV600E mutation in the differential diagnosis of unicystic ameloblastoma with dentigerous and radicular cysts. Twenty-six archival samples were included, comprising eight unicystic ameloblastomas (UAs), nine dentigerous and nine radicular cysts. The mutation was assessed in all samples by anti-BRAFV600E (clone VE1) immunohistochemistry (IHC) and by TaqMan mutation detection qPCR assay. Sanger sequencing was further carried out when samples showed conflicting results in the IHC and qPCR. Although all UAs (8/8) showed positive uniform BRAFV600E staining along the epithelial lining length, the mutation was not confirmed by qPCR and Sanger sequencing in three samples. Positive staining for the BRAFV600E protein was observed in one dentigerous cyst, but it was not confirmed by the molecular methods. Furthermore, 2/9 dentigerous cysts and 2/9 radicular cysts showed non-specific immunostaining of the epithelium or plasma cells. None of the dentigerous or radicular cysts cases presented the BRAFV600E mutation in the qPCR assay. The BRAFV600E antibody (clone VE1) IHC may show non-specific staining, but molecular assays may be useful for the diagnosis of unicystic ameloblastoma, in conjunction with clinical, radiological and histopathological features.

Pereira NB ，Pereira KM ，Coura BP ，Diniz MG ，de Castro WH ，Gomes CC ，Gomez RS ... -  《-》

Syndecan-1 (CD 138) surface expression marks cell type and differentiation in ameloblastoma, keratocystic odontogenic tumor, and dentigerous cyst.

The altered expression of syndecan-1 (SD-1), a transmembrane heparan sulfate proteoglycan, in ameloblastomas and cysts of odontogenic origin suggests that this molecule could have prognostic value in assessing the clinical outcome of those lesions. The purpose of this study was to analyze SD-1 expression profile immunohistochemically in archival, paraffin-embedded tissue sections of ameloblastomas and in common odontogenic cysts arising from the same locale. SD-1 expression was investigated in 32 ameloblastomas, 26 keratocystic odontogenic tumors (KCOT), and 21 dentigerous cysts from the archives of the histopathology laboratory which were routinely processed. The cases were reviewed and assessed according to the established criteria. Sections were immunostained with monoclonal antibody against SD-1 (CD138). Sections of normal oral mucosa, site matched, were stained in parallel as positive controls. The plasma cells in sections served as internal positive controls. SD-1 expression was observed in the epithelial and stromal elements of the sections, and the expression was significantly associated with the lesion's extension and involvement of adjacent structures (P=0.025). Stellate-reticulum cells showed higher expression than the ameloblasts, which was at a significant level (P<0.0001). Highly significant difference was reported among the three groups of lesion for the epithelial staining (P<0.0001). The mean rank scores (Kruskal-Wallis test) of ameloblastomas were significantly lower than those of KCOT and dentigerous cysts. Non-significant comparison was made between KCOT and dentigerous cyst groups. The present study revealed SD-1 immunoreactivity in the stromal cells of ameloblastoma, KCOT, and dentigerous cysts rather uniformly. This reported SD-1 expression by the tumor stroma is considered to be associated with poor prognosis of the lesions.

Al-Otaibi O ，Khounganian R ，Anil S ，Rajendran R ... -  《-》

Use of calretinin in the differential diagnosis of unicystic ameloblastomas.

Coleman H ，Altini M ，Ali H ，Doglioni C ，Favia G ，Maiorano E ... -  《-》

Dentigerous Cyst and Ameloblastoma of the Jaws.

Barrett AW ，Sneddon KJ ，Tighe JV ，Gulati A ，Newman L ，Collyer J ，Norris PM ，Coombes DM ，Shelley MJ ，Bisase BS ，Liebmann RD ... -  《-》