The process of programmed cell death, or apoptosis, has become one of the most intensively studied topics in the biological sciences during the last three decades. Apoptosis as a common and universal mechanism of cell death, distinguishable from necrosis, is now a widely accepted concept due to the paper by Kerr et al. in the early seventies. Apoptosis is the most popular death mechanism as found in the research literature. Although the apoptosis in many other tissues is well documented, the apoptosis of the oral region has only recently been published. This review will focus, therefore, on the apoptosis and apoptosis-related lesions at the field of the oral region.

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In order to clarify the histopathological changes of oral mucosa induced by low iron conditions, rat tongue epithelia in low iron conditions were examined histologically. Sprague-Dawley rats (3 weeks old) were divided into 2 groups. The experimental group (E group n=10) was given a low iron diet (PMI.Test Diet 5895,<5mg Fe/kg diet), while the control group (C group n=10) was fed a standard laboratory diet (NIHON CLEA, CE-II, 347 mg Fe/kg diet). Animals were sacrified after 8 weeks and 18 weeks, and their tongues were removed and histologically analyzed by H-E staining, SEM and histochemistry with anti-PCNA staining. Although histological changes of tongue papilla were not observed, epithelial dysplasia was demonstrated in some rats of E-group, and a significant increase in the percentage of PCNA positive cells in basal and para basal cell layers were observed in E-group when compared with that of C group (65% in E group, 7% in C group, 8 weeks; 50% in E group, 7% in C group, 18 weeks). Our results suggest that the increase in mitotic activity of tongue epithelia can be induced by the administration of a low iron diet.

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The objective of this reserch is to investigate the age-related changes of human taste buds in circumvallate papillae by a histomorphometric study. The materials were obtained from 241 Japanese cadavers, ranging in age from 0 to 97 years old. The taste bud numbers in the papilla wall, and the taste bud cell numbers per taste bud section were calculated. The transcriptional activities of taste bud cells and lingual epithelial cells were investigated by the argyrophilic nucleolar organizer regions (AgNORs) technique. The taste bud density and the taste bud cell density in the older age groups was lower than that of the younger age groups. The AgNOR number of lingual epithelial cells decreased significantly in the older age groups, but the taste bud cells did not. Unlike the maintenance of transcrptional activity of taste bud cells, the reduction in the taste bud density and the taste bud cell density may influence taste systems with aging.

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A case of benign mesenchymoma that occurred in the cheek is presented. The tumor consisted of an admixture of such mesenchymal elements as mature fat tissue, blood vessels of varing size and shape with less organized muscular wall, fascicles of smooth muscle cells, and bone. Immunohistochemical examination revealed that many smooth muscle cells comprising the tumor were positive for desmin and α-smooth muscle actin but negative for vimentin. Such an immunohistochemical characteristic is very similar to that of non-vascular smooth muscle cells.

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An autopsy case of verrucous carcinoma with anaplastic transformation is reported upon. A 76-year-old woman with a warty tumor accompanying marked purulent inflammation 15 years after primary treatments including irradiation for carcinoma that had originated from the floor of the mouth was examined. An autopsy revealed that the tumor, straddling oropharyngeal and cervical regions, exhibited exophytic growth and deeply invaded with slight atypia. No metastasis was observed, but a small focus of anaplastic squamous cell carcinoma was located in the root of the tongue.

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A case of acanthomatous ameloblastoma with melanin pigmentation occurring in the maxilla of a 27-year-old Japanese woman is reported. The microscopic examination of the biopsy and excision specimens of the tumor revealed proliferating ameloblastic tumor cells with a network of anastomosing strands. Within some epithelial strands, discrete foci of squamous metaplasia progressing to keratin pearl formation and dystrophic calcification were observed. Dark brown melanin granules were scattered in proliferating tumor nests and stromal connective tissue.

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We reported a case of a clear-cell variant, which is a histologically rare type of mucoepidermoid carcinoma, arising from the parotid gland of a 38-year-old Japanese female. Microscopically, most of the tumor nests were composed of clear cells surrounded by cuboidal epidermoid cells. A part of the tumor nest appeared to have tubular structures without clear cells. Although most of the clear cells had no reaction to PAS , alcian blue or mucicarmine, a few isolated clear cells showed positive reactions. Immunohistochemically, the tubular structures without clear cells showed positive reactions to keratin, S-100, CEA and EMA. The tumor nest of clear cells reacted to only keratin. From these results and a review of the existing literature, it is thought that the clear-cell variant of mucoepidermoid carcinoma may be closely related to pleomorphic adenoma.

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A case of intravascular papillary endothelial hyperplasia of the lower lip in a 26-year-old male is described. It exhibited a rapid growth of two weeks duration and trauma may have played a decisive role in inducing the lesion. The lining cells of papillary structures showed positivity to factor VIII-related antigen.

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