Immunohistochemical detection and ultrastructure of myofibroblasts in the stroma of odontogenic cysts and ameloblastoma

Immunohistochemical phenotype, distribution and significance of proliferation of myofibroblasts [alpha SMA positive cells] with evaluation of ultrastructure, in dentigerous cyst, odontogenic keratocyst and ameloblastoma were analyzed. The study included paraffin embedded blocks of ameloblastoma [n=22], odontogenic keratocyst [n=20], and dentigerous cyst [n = 18]. The expression of alpha SMA was determined by immunohistochemically stained section. The percentage of positive cells was calculated from a minimum of 1000 cells and H-score was expressed [% positive cells x intensity of staining]. For transmission electron microscopy, fresh specimens were obtained from three patients and were fixed in 2.5% glutaraldehyde. The presence of cells with the ultrastructural characteristics of the myofibroblast was recorded. The mean number of positive cells in the three groups was significantly different. The difference between odontogenic keratocyst and dentigerous cyst and also the difference between dentigerous cyst and ameloblastoma were not statistically significant. The mean number of positive cells in the odontogenic keratocyst was significantly higher than that in ameloblastoma. In ultra-structural evaluation, myofibroblasts exhibited abundant cytoplasmic microfilaments, basal lamina-like material, subsurface caveolae, pinocytic vesicles, rough endoplasmic reticulum, and mitochondries. The high frequency of stromal myofibroblast in the odontogenic keratocyst implies that myofibroblast can contribute to aggressive nature of this cyst, but between odontogenic cysts and ameloblastoma, the presence of stromal myofibroblast has no correlation with invasiveness

[Quantitative analysis of argyrophilic nuclear organizer regions in different histological grading of mucoepidermoid carcinoma]

Mucoepidermoid carcinoma [MEC] is one of the most common malignancies of the salivary glands. Since the microscopic grading of this tumor is one of the important factors for determining the treatment plan and prognosis, it should have standard and applicable criteria. The AgNORs method is able to determine grading, prognosis and power of proliferation of tumors and can be applied for Mucoepidermoid carcinoma grading. The aim of this study was to assess cellular proliferation in salivary glands mucoepidermoid carcinoma with quantitative comparison of AgNORs and its relation to histological grading. In this descriptive-analytical study, 42 formalin fixed paraffin embedded blocks of mucoepidermoid carcinoma were selected. Five cases were eliminated due to the exclusion criteria and 37 cases including 15 low grades MEC, 11 intermediate grade MEC, and 11 high grade MEC were studied. After AgNORs processing, NORs were counted by light microscope in magnification 1000. The data were analyzed statistically using ANOVA test. Mean AgNORs count for high, intermediate and low grade MEC was 1.65 +/- 0.73, 1.1 +/- 0.35, and 0.76 +/- 0.32, respectively. There was a significant difference in AgNORs count among the three groups [p<0/05]. The findings of this study indicated that this method can be used for microscopic grading of MEC as an accessory method. Future studies are recommended to determine sensitivity and specifity of this method