The purpose of this study was to evaluate the effects of nicotine on Malassez' epithelial rest (MER) cells which are thought to maintain the homeostasis of the periodontal ligament. MER cells obtained from porcine periodontal ligament were cultured for 7 days, after which nicotine was added to the culture medium at concentrations of 0.03 μM, 0.15 μM or 0.2 μM. Cells cultured without nicotine were used as controls. Cell proliferation and expression of mRNAs encoding heat shock protein 70 (HSP70) and vascular endothelial growth factor (VEGF) were analyzed to evaluate the effects of nicotine. The cell proliferation ratios of all nicotine-treated groups were significantly lower than the control group on day 7. The expression of HSP70 mRNA in all nicotine-treated groups was higher than in the control group. The expression of VEGF mRNA in all nicotine-treated groups at all times examined tended to be lower than in the control groups. In conclusion, nicotine affects MER cells by increasing mRNA expression of HSP70, but decreasing that of VEGF.

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The progenitor cells of odontoblasts have been considered to be undifferentiated dental pulp cells positive for α-smooth muscle actin (α-SMA). α-SMA is also expressed in vascular smooth muscle cells, which are well-known to differentiate into osteoblastlike cells. The osteogenesis is up-regulated under hyperglycemic conditions. Proliferation and differentiation of dental pulp cells are also considered to be upregulated under high-glucose conditions. The present study was designed to clarify the relation among human dental pulp cells (HDPCs), odontoblast progenitors and odontogenesis. Differentiation of HDPCs into odontoblasts was confirmed by examining ALP activity and calcified nodules as well as gene expressions of osteocalcin and dentin sialoprotein. The endothelial cell marker eNOS and mural cell markers, NG2, calponin and α-SMA, were immunostained. Both proliferation and differentiation of HDPCs were up-regulated in high-glucose media. NG2 and calponin proved to be more suit ble markers for odontoblast progenitors than α-SMA. Odontogenesis may be related to endothelial cells.

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We investigated the immunohistochemical characteristics of 13 cases of odontogenic carcinoma, including 3 cases of ameloblastic carcinoma, 9 cases of primary intraosseous squamous cell carcinoma (PIOSCC), and 1 case of ghost cell odontogenic carcinoma (GCOC), to elucidate the origin and determine diagnostic markers of odontogenic carcinoma. Thirty cases of gingival squamous cell carcinoma (gSCC) were included for comparison. All ameloblastic carcinomas and GCOC cases, as well as 6 of 9 PIOSCC cases, exhibited immunoreactivity for CK19, whereas only 3 of 30 gSCC cases were positive for CK19. Two cases of ameloblastic carcinoma and only 1 case of PIOSCC expressed CD56; however, CD56 was not expressed in any gSCC cases. All odontogenic carcinoma cases except a single GCOC case were negative for calretinin. These findings indicate that immunoreactivity to CK19 is useful to identify odontogenic origin of the odontogenic carcinomas including PIOSCC, and it may also be useful for distinguishing PIOSCC from gSCC.

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Patients with autoimmune and chronic inflammatory conditions are at increased risk of developing lymphoma. We report a case of extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) in a 60-year-old woman who has been treated for Sjögren's syndrome for the last 8 years. She was referred to our hospital because of a painless swelling in her left lower lip. There were no clinical signs of major salivary gland swelling or systemic lymphadenopathy. The tumor was removed surgically, and microscopic examination showed it to be characterized by lymphoepithelial lesions, proliferation of centrocyte-like cells, and follicular colonization, leading to the diagnosis of MALT lymphoma. The patient has undergone periodic systemic examination without evidence of tumor recurrence for 18 months since the surgical treatment. The present report supports the postulation that the labial salivary gland biopsy can offer early diagnostic clues to lymphoma development in patients with underlying Sjögren's syndrome.

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An intraneural perineurioma arising in the tongue of a 34-year-old woman is presented. Histologically, the tumor was composed of numerous pseudo-onion bulb structures, formed by whorled proliferation of spindle cells around axons. Immunohistochemically, the spindle cells were positive for epithelial membrane antigen (EMA) but negative for S-100 protein, indicating that the tumors cells were derived from perineurial cells.

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We report a case of an 81-year-old female patient presenting a dome-shaped swelling at the tip of the tongue, pathologically diagnosed as giant cell fibroma. Histologically, the fibrous lesion contained abundant characteristic stellate giant cells (mono-, bi-, and multinucleate), the localization and morphology of which were consistent with that reported previously. The immunohistochemical profile of stellate giant cells was also generally consistent with previous reports, suggesting that such cells would chiefly be of the fibroblastic lineage. Our case was unique because the stellate giant cells were often in close proximity with human leukocyte antigen DR (HLA-DR)-positive spindle/dendritic cells and rarely showed S-100 protein positivity. These findings suggest that a minor subset of stellate giant cells could be monocytemacrophage lineage, although the majority was thought to represent fibroblastic lineage.

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