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To examine the expression of p53 protein and gene alterations in oral epithelial lesions including epithelial dysplasias and primary squamous cell carcinomas, immunohistochemical and temperature gradient gel electrophoresis (TGGE) methods were applied to formalin-fixed and paraffin-embedded tissues. Morphologically normal mucosal epithelium stained negatively for p53 protein. Three out of 11 (27.3 per cent) epithelial dysplasias and 19 out of 57 (33.3 per cent) primary squamous cell carcinomas stained positively for p53 protein. Although more than half of the cases were positive for p53 protein in stage I, the positive cancer cases were found at other stages with variable frequency. Immunoreactive products were localized in the nucleus, especially in the basal and suprabasal layers. The analysis by TGGE revealed gene alterations in exons 5-8 in 3 out of 3 epithelial dysplasias and 17 out of 19 (89.5 per cent) primary squamous cell carcinomas which were immunohistochemically positive for p53 protein. These results suggest that p53 gene mutation may be involved in carcinogenesis in the oral squamous epithelium even in the early stage of the dysplasia-carcinoma sequence.

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A case of metastatic thyroid carcinoma near the left mandibular ramus with a cyst-like appearance on rotational panoramic radiographs is reported. A 55-year-old woman complained of a continuous sense of incongruity for 3-4 years since extraction of the left mandibular third molar. The lesion, with apparent gingival swelling around the left second molar, was painless and was cyst-like in appearance on plain radiographs. On the basis of the radiological fi ndings, a benign odontogenic tumor was suspected, but computed tomography (CT) showed destruction of the lingual cortical bone with soft tissue invasion to the masticator space. The fi nal histopathological diagnosis was metastatic follicular carcinoma of the thyroid gland. When investigating cyst-like radiolucent lesions with thick sclerotic margins and irregular areas on plain radiographs, we recommend using CT to evaluate the effect of the lesion on cortical bone.