The purpose of this article is to review recent experimental studies on oral tumors including the odontogenic tumors which were produced by a combination of carcinogen application with physical wounding. Many experimental studies on carcinogenesis have suggested that physical wounding or mechanical stimulation is sufficient to promote the growth of both benign and malignant neoplasms. Furthermore, a novel genome of papillomavirus was identified in these dysplastic and cancer lesions produced in hamsters . The interactions between chemical carcinogens, physical irritations and papillomavirus in carcinogenesis are also described.

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The present study was undertaken to investigate the effects of systemic HEBP (1-hydroxyethylidene-1, 1-bisphosphonate) administration on the alveolar bone structure at the intraradicular region of rat lower molars. Male Wistar rats (about 100 g b.w.) were divided into three groups: (a) animals kept with drinking water containing 1% HEBP throughout the housing periods covering 4 days through 8 weeks; (b) animals given the same HEBP-containing water during the initial 4 weeks, thereafter being kept with HEBP-free drinking water for various periods (4-28 days) ; and (c) animals kept free from HEBP during the corresponding periods as the control group. The tooth specimens were examined by histometric analysis in conjunction with H.E., van Gieson, and TRAP stainings; or by microradiography. The results obtained evidenced that: 1) systemic administration of 1% HEBP stimulated the outgrowth of osteoid due to hindrance of mineralization onto the deposited bone matrix and osteoclastic resorption activity, giving rise to obliteration of the periodontal space (development of focal ankylosis) ; and 2) after cessation of the HEBP administration, TRAP-positive osteoclasts penetrated into the ankylosed areas, leading to reconstruction of the periodontal structure within the following 3 to 4 weeks. It is pertinent that the use of HEBP to rat provides an experimental model for pathogenesis of the osteoid-mediated ankylosis and its reversible recovery.

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The purpose of this study is to quantitatively evaluate differences in consistency among different parts of the tongue and the floor of the mouth. Sixteen healthy young adults were examined using an instrument capable of measuring consistency as a function of the load (in grams) needed to displace oral mucosa 2.0mm by a probe 2.0mm in diameter. The mean values of consistency (SD; standard deviation) of normal mucosa were 5.0g (2.8), 4.5g (2.6), 3.8g (2.4), 3.4g (1.9), corresponding to inferior surface of tongue, dorsum of tongue, floor of the mouth, and lateral surface of tongue, respectively. Furthermore, consistency varied among smaller areas, such as superior, inferior, medial, lateral, anterior, or posterior, in each part. This study demonstrates that there are subtle differences in consistency of the tongue and floor of the mouth depending on the different regions.

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To clarify pathogenic roles of human papillomavirus (HPV) in tumorigenesis, 111 specimens of oral lesions were examined by Southern blot hybridization (SBH) and polymerase chain reaction (PCR) using a set of primers, L1C1/L1C2 and L1C2m (L1-PCR). The specimens consisted of 9 papillomas, 34 leukoplakias, 36 squamous cell carcinomas (SCC), 12 fibrous polyps, 6 epulis fibrosas and granulomatosas,8 normal mucosa collected at operation, and 6 normal tongues taken at autopsy. HPV DNA was detected not by SBH but by PCR with higher frequency in papilloma (5/9; 55.6%), as compared with in leukoplakia (7/34; 20.6%), SCC (7/36; 19.4%), fibrous polyp (3/12; 25%), normal mucosa at operation (1/8; 12.5%) and at autopsy (3/6; 50%). By direct sequencing of the PCR products for genotyping in 26 HPV DNA-positive specimens, HPV-18 was detected in 23 (88.5%), -59 in 2(7.7%) and -70 in 1(3.8%). HPV-70 was first identified in the oral papilloma lesions.

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A case of eosinophilic ulcer (EU) of the oral mucosa is described. The patient was a 73-year-old woman who had suffered indurated ulcer on the tongue of two months' duration. After biopsy, the ulcer completely healed without treatment. The lesion is interpreted as a mixed infiltrate of large mononuclear histiocytes with slight atypia, eosinophils and lymphocytes. The histiocytic component was nonreactive for the ordinary macrophage markers except for CD 68. The majority of lymphocytes were positive for CD 45 RO. In addition, vimentin (+), α-smooth muscle actin (+) and desmin (-) myofibroblasts were scattered throughout. The importance of EU is that it simulates malignancy and can lead to overtreatment for what is a florid but reactive process.

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A case of atypical meningioma, which invaded the extracranial tissue and resulted in the broad swelling of the right temporomandibular region, is reported. A 53-year-old male had a lesion with a combination of osteolytic and osteoplastic reactions in the temporal bone, which was clinically diagnosed as malignant neoplasm or osteomyelitis. The biopsy specimen revealed that invading nests show biphasic immunoreactivity of vimentin and EMA, micronecrosis and over-expression of p53. However, mitosis and Ki-67 labelling indices of tumor cells were estimated to be less than 2/10 HPFs and 5.8% respectively, so that this case was diagnosed as atypical meningioma.

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We report a case of squamous cell carcinoma of the tongue with a sarcomatoid micronodule in a 76-year-old man. A white lesion with erosion was observed on the right inferior surface of the tongue, and carcinomatous change of leukoplakia was suspected. Microscopic examination of a biopsy specimen revealed a micronodular proliferation of spindle cells with continuity to invasive squamous cell carcinoma . Although spindle cells did not demonstrate epithelial characteristics immunohistochemically , S-100 protein-positive cells were observed among them. Based on these findings, sarcomatoid differentiation of squamous cell carcinoma to nerve sheath cells, myofibroblasts or Langerhans cells was suggested.

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An autopsy case of malignant ameloblastoma in a 64-year-old Japanese woman is presented, which started as a benign ameloblastoma with plexiform and follicular patterns, and transformed into a malignant histology with atypical and mitotic tumor cells in the course of several recurrences. An autopsy revealed several relatively large metastases in the lungs bilaterally consisting of malignant ameloblastoma and intracranial invasion of malignant tumor cells to the left temporal lobe. Immunohistochemical staining of proliferating cell nuclear antigen (PCNA) demonstrated a significant increase in the proliferative activity of neoplastic cells between the primary tumor and two recurrent ones (P < 0.01, Newman-Keul's test). This data provides evidence of malignant transformation in a benign ameloblastoma in the course of multiple recurrences. Immunostaining of PCNA may be useful in determining the possibility of malignant transformation in recurrent cases of ameloblastoma.

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