We report here a rare case of malignant myoepithelioma occurring in the maxilla, accompanied by extensive osteoid formation. The patient was a 20-year-old Japanese man with a rapidly swelling mass in the hard palate. Expressions of bone sialoprotein (BSP) and osteopontin (OPN) were examined by immunohistochemistry, in situ hybridization (ISH) and RT-PCR. The mass showed invasive growth of atypical spindle and polygonal cells with abundant osteoid tissue in the stroma. These cells retained immunohistochemical features of myoepithelium, characterized by positive reactivity for cytokeratin (WS), cytokeratin 14, S-100 protein, vimentin, smooth muscle myosin heavy chain and calponin. In addition, malignant myoepithelium noted in and around the osteoid tissue showed expression of BSP on immunohistochemical analysis and ISH, but with no expression of OPN. The normal salivary gland tissue was negative for BSP and OPN. These results suggested that BSP might play a significant role in osteoid development in the present case.

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The NQO1 gene, encoding the phase II drug-metabolizing enzyme NAD(P)H:quinone oxidoreductase 1 (NQO1), is regarded as an important enzyme for susceptibility to carcinogenesis in humans. Japanese people show a polymorphism (C609T) in NQO1 as C in the wild-type genotype (wt) and T in the variant genotype (vt). In this study of 105 patients with oral squamous cell carcinoma (OSCC), the wt/wt, wt/vt and vt/vt genotypes were found in 42, 49 and 14 cases, respectively, while each genotype was detected in 49, 52 and 1, respectively, of 102 control cases with no carcinoma at any site in the body. The χ² test revealed that individuals with the vt/vt genotype were less common in the control cases than in the OSCC patients (P < 0.001) and the odds ratio of the vt/vt to the wt/wt genotype was 16.3. The results indicate that susceptibility to OSCC appears to depend significantly on the NQO1 polymorphism.

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A 81-year-old female had suffered from a white lesion in the right lateral margin of the tongue for 10 years. The lesions was surgically removed and examined histopathologically. The surgical specimen showed small foci of squamous cell carcinoma invading up to 4 mm in the muscle layer with a diameter of less than 7 mm in the central portion. The carcinomatous foci were surrounded by epithelial dysplasia in various degrees with a dense lymphocytic infiltration in the lamina propriae. Some of the dysplasia parts just next to the carcinomatous foci contained obviously atypical cells without basal cell alignment but with an apparent keratinizing tendency, which could not be otherwise diagnosed as carcinoma in-situ. Based on this case report, a new concept of carcinoma in-situ of the oral mucosa was proposed, because the histology was different in terms of keratinization degree from so-called carcinoma in-situ as frequently seen in the cervix uteri, which were mainly composed of proliferation of basaloid cells.

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The presence of human papillomavirus (HPV) in two groups of oral squamous cell carcinoma (OSCC) from Sri Lanka were analyzed by PCR and direct cycle sequencing using consensus GP5+/6+ primers. The two groups of OSCC specimens analyzed were 68 formalin-fixed paraffinembedded surgical specimens and 34 formalin-fixed unembedded biopsies. Twenty-five patients from the latter group were habitual betel quid chewers. The HPV prevalence of the overall sample was 38/102 (37.2%). However, HPV was detected in significantly higher rate from formalin-fixed unembedded biopsies (61.7%) compared to paraffin embedded surgical specimens (25%) (p<0.0003). Upon sequencing, high-risk HPV types, 16,18, 45 and 66 were detected in 65% of the HPV infected tumors. Moreover, HPV was detected at significantly higher rates from small primary tumors (T1&T2) (75%) compared to large primary tumors (T3&T4) (30%) (p<0.025). However, no correlation existed between other clinico-pathological variables such as age, gender, sites, habits or histological differentiation and HPV detection when analyzed statistically using Pearson's chi-square test (at 5% level of significance). In conclusion, high prevalence of HPV in formalin fixed-unembedded OSCC biopsies from Sri Lanka indicate that, in addition to betel quid, viral infection may play a role in oral carcinogenesis and support the multi-factor model for oral cancer causation.

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We present the case of a 20-year-old female with micrognathia associated with Hallermann-Streiff syndrome. Successful surgical extension of the mandible was achieved by sagittal splitting osteotomy and genioplasty using a porous hydroxyapatite block graft. Titanium dental implants were used to correct malocclusion due to congenital partial adontia. The clinical course has been satisfactory with no functional or cosmetic abnormalities as of 15 years postoperatively.

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A case of a dentigerous cyst associated with a malformed supernumerary tooth is reported, and the clinicopathological characteristics of dentigerous cysts with abnormal dentition are reviewed from the literature and our hospital records. A 7-year-old boy had a painless and radiolucent lesion in his right molar region of the mandible. Radiographic examinations revealed that a well-defined cystic lesion, measuring 20 mm in diameter and containing a toothlike calcified structure, was located between the first and second molar tooth germs. Histopathologically, the cyst wall was composed of fibrous granulation tissue with a squamous epithelial lining. The calcified structure was a reversely concaved tooth crown which protruded into the cystic lumen with its enamel layer at the inner surface. The cyst lining epithelium was continuous with the reduced enamel epithelium covering the malformed tooth. A review of the literature and a case survey in our hospital showed that about 10% of dentigerous cysts were associated with supernumerary teeth which were mostly located in the median region of the maxilla, but that those in the mandibular molar region were extremely rare.

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