Diagnostic value of MRI for odontogenic tumours.

OBJECTIVES: To evaluate the diagnostic value of MRI for odontogenic tumours. MATERIALS AND METHODS: 51 patients with odontogenic tumours were subjected to pre-operative MRI examinations. For tumours with liquid components, i.e. ameloblastomas and keratocystic odontogenic tumours (KCOTs), the signal intensity (SI) uniformity of their cystic components (UΣ) was calculated and then their UΣ values were compared. For tumours with solid components that had been examined using dynamic contrast-enhanced MRI (DCE-MRI), their CImax (maximum contrast index), Tmax (the time when CImax occurred), CIpeak (CImax × 0.90), Tpeak (the time when CIpeak occurred) and CI300 (i.e. the CI observed at 300 s after contrast medium injection) values were determined from CI curves. We then classified the odontogenic tumours according to their DCE-MRI parameters. RESULTS: Significant differences between the UΣ values of the ameloblastomas and KCOT were observed on T1 weighted images, T2 weighted images and short TI inversion recovery images. Depending on their DCE-MRI parameters, we classified the odontogenic tumours into the following five types: Type A, CIpeak > 2.0 and Tpeak < 200 s; Type B, CIpeak < 2.0 and Tpeak < 200 s; Type C, CI300 > 2.0 and Tmax < 600 s; Type D, CI300 > 2.0 and Tmax > 600 s; Type E, CI300 < 2.0 and Tmax > 600 s. CONCLUSION: Cystic component SI uniformity was found to be useful for differentiating between ameloblastomas and KCOT. However, the DCE-MRI parameters of odontogenic tumours, except for odontogenic fibromas and odontogenic myxomas, contributed little to their differential diagnosis.

Expression of human beta-defensin -1, -2, and -3 in non-inflamed pseudocyst, mucoceles.

OBJECTIVES AND DESIGN: The expressions of human beta defensin-1 (HBD-1), -2 (HBD-2) and -3 (HBD-3) in non-inflamed pseudocysts such as mucoceles were investigated immunohistochemically in this study. MATERIALS AND METHODS: Mucocele specimens were obtained from 21 patients. The expression of HBDs was studied immunohistochemically by using antibodies directed against HBD-1, -2, and -3. Statistical analyses were carried out on serial sections stained with antibodies. RESULTS: Cells expressing HBDs were found in mucoceles. The expression of HBD-2 was observed in floating cells in all the specimens, whereas HBD-1 and HBD-3-expressing cells were detected in 93% and 73% of the mucoceles, respectively. The HBD-2 signal was the most intense and the HBD-3 signal intensity was weaker than that of HBD-1. HBDs were expressed in neutrophils and in other floating cells. Interestingly, the signal intensity and the population of positive cells located close to the centers of cysts were higher than those located in the peripheral areas of cysts. CONCLUSION: The expression of HBDs was found even in non-inflamed pseudocysts such as mucoceles. These results suggest that an unknown mechanism not involved in biophylaxis for the expression of HBDs may exist.