A comparative study of the oral epithelia of inflammatory hyperplasias and the dysplastic epithelia of oral squamous cell carcinoma by transmission electron microscopy

Abstract

ObjectiveThis study aims to compare the atypical epithelial changes of oral inflammatory lesions with the dysplastic epithelial changes of oral squamous cell carcinomas and to examine the underlying pathogenetic mechanisms that cause the changes by transmission electron microscopy (TEM). MethodsEight cases of parulides (oral inflammatory lesions) and 10 cases of oral squamous cell carcinomas were studied. Each specimen was cut into two pieces: one piece was fixed in a neutral buffered 10 % formaldehyde solution and prepared for light microscopy, and the other was fixed in a cold, 2.5 % glutaraldehyde solution and prepared for TEM. ResultsBased on the six histopathologic criteria in this study, both types of epithelia showed similar ultrastructural features, but some significant differences are observed as follows: In parulides, the epithelial cells with features similar to abnormal mitoses showed nuclear fragments with chromatin condensation (karyorrhexis), and no discernible organelles in the cytoplasm, indicating that these are necrotic cells. In contrast, in oral squamous cell carcinomas, the epithelial cells with abnormal mitotic figures showed clumping of chromosomes with abnormal mitotic spindles, indicating that these are abnormally dividing cells. Abnormal keratinization was also seen. The nuclei of the abnormally keratinized cells were irregular with coarse and clumped chromatin. ConclusionsThe atypical epithelial changes in oral inflammatory lesions are a result of necrotic changes in the epithelia due to underlying inflammatory processes and are not true epithelial dysplasia. In contrast, the dysplastic epithelial changes in oral squamous cell carcinomas are dysplastic changes due to premalignant neoplastic processes.