[Enamel structure of atypically formed human teeth].

Using light and scanning electron microscopy thin epoxide processed sections of 12 impacted third molars, one molar developed in odontogenic follicular cyst and one tooth-like teratoma were studied. It was established that the 4 impacted teeth and the tooth developed in odontogenic follicular cyst had obvious signs of enamel damage in the form of erosion in the crown fissures. The features of enamel alteration make it possible to interpret the changes as carious process which apparently has endogenous origin. Tooth-like teratoma extracted from ovarian dermoid cyst looked like canine and incisor "hybrid" coronal portion of which is covered with thin enamel layer, marked by obvious signs of multiple erosive lesions of endogenous nature. But unlike alterations in impacted teeth it resembles either fluorosis or enamel hypoplasia.

Quantitative and qualitative analysis of argyrophilic nuclear organizer regions in follicular cyst, keratocystic odontogenic tumor and ameloblastoma.

BACKGROUND: Multicystic ameloblastoma is a benign odontogenic tumor that exhibits a more aggressive behavior than keratocystic odontogenic tumor (KCOT) and follicular cyst. AIM: The purpose of the study was to evaluate the proliferation index nuclear organizer regions (NORs) and their distribution among the four odontogenic lesions with known different clinical invasive behavior. STUDY AND DESIGN: In a descriptive-analytical cross-sectional study, 60 paraffin blocks of odontogenic lesions were prepared for silver nitrate staining. MATERIALS AND METHODS: For the quantitative analysis, 100 cells were counted at ×100 and the mean value was calculated. The morphometric analysis of NORs showed that they can be distributed into normal (round to oval-shaped) and abnormal (large, bean-shaped and cluster-shaped) groups. One-way analysis of variance (ANOVA) and multiple comparison with Tukey test were used for the statistical analysis of the results. RESULTS: The argyrophilic NOR (AgNOR) numbers in multicystic ameloblastoma, unicystic ameloblastoma, KCOT, and follicular cyst were 7.4 ± 2.7, 6.1 ± 2.56, 4.7 ± 1.84, and 2.82 ± 1.052, respectively. The difference between ameloblastoma (unicystic and multicystic types) and either_KCOT, or follicular cyst was statistically significant (P<0.001) and, (P=0.001), respectively. In follicular cysts, normal AgNOR dots were not detected outside the nuclei. NOR histological patterns of KCOT were large, bean shaped and rarely cluster shaped and it was cluster-shaped in multicystic and unicystic ameloblastoma. CONCLUSION: The current study suggests that determination of clinical behavior of ameloblastoma in comparison with KCOT and follicular cyst in silver nitrate staining is related to higher proliferation activity and different NORs' distribution pattern. However, further clinical follow-up studies must be performed to prove this.

Colloid cyst of the third ventricle: a comparative ultrastructural study of neuraxis cysts and choroid plexus epithelium.

Thirteen colloid cysts (CC), four Rathke cleft cysts (RCC), three follicular cysts of normal pituitary gland (FCP), four enterogenous cysts (EC), three normal choroid plexi (CP), three choroid plexus papillomas (CPP), and several samples of normal bronchial mucosa and ependyma were studied by electron microscopy. The ultrastructure of most of the CC was indistinguishable from that of RCC, FCP, EC, and normal bronchial mucosa in demonstrating nonciliated and ciliated epithelial cells, goblet cells, basal cells, and intermediate forms, some showing evidence of early squamous differentiation. Two CC displayed mostly squamous differentiation, and one contained basally situated cells resembling myoepithelial cells. Although the RCC and FCP displayed features similar to those of CC, they also contained cells with electron-dense granules indicating pituitary hormone production and scattered cells showing oncocytic change. EC were lined by either squamous cells or mucin-producing columnar cells. Every CC, RCC, FCP, and EC contained cells covered by glycocalyx. In contrast to aforementioned lesions, ependymal lining, CP, and CPP were composed of a single cell type, one with numerous villi, few cilia, and no signs of keratinization, mucin production, or glycocalyx coating. It is concluded that the ultrastructural properties of CC are the same as those of cysts of endodermal or ectodermal origin and of respiratory mucosa. No ultrastructural similarities were observed between CC and normal or neoplastic neuroepithelium. These ultrastructural findings support the concept of an enterogenous origin of colloid cysts and highlight their similarity to RCC.

Hair matrix differentiation. Occurrence in lesions other than pilomatricoma.

The formation of structures resembling hair matrices is the least common form of follicular differentiation and only occurs with any frequency in pilomatricoma. Rarely, follicular cysts and both benign and malignant adnexal tumors can show areas of pilomatricoma-like change, or hair matrix differentiation. Examples of focal hair matrix differentiation in a follicular cyst, a cutaneous mixed tumor, and an adnexal carcinoma are presented. Each of these cases also demonstrates the presence of limited differentiation toward structures of the inner root sheath.