According to the literature regarding the intraoral ultrasonography application for the diagnosis of tongue carcinoma, a tumor invasion area had been demonstrated as hypoechoic compared with the surrounding structure. However, especially with the recently released high-resolution intraoral probe, histopathological invasion front did not always correspond with the deepest margin of the hypoechoic area because the invasion front always tended to be affected by various degree of inflammatory reaction.

　With regard to the significant CT findings for the early detection of the lymph node metastases, CT perfusion might be one of the promising method in cases without obvious central necrosis.

Cancer is now the leading cause of death in Japan. A rapid increase in cancer mortality is expected as Japan is facing as uper-aged society. Oral cancers rank sixth among the common malignancies globally, with a rising titer of around 40% in developing countries such as Southeast Asia. More than 90% of malignant neoplasms of the oral cavity and oropharynx are squamous cell carcinomas of the lining mucosa. Review of the literature indicates that the most important factor for the high mortality rate is the advanced stage of the disease at the time of diagnosis and treatment. In the prognosis of oral cancer, the extent of lymph node metastasis is a major determinant. Like most epithelial cancers, oral cancer develops through the accumulation of multiple genetic and epigenetic alterations in a multistep process. Recent molecular studies have advanced our understanding of the disease and provided a rationale to develop novel strategies for early detection, classification, prevention, and treatment. Attempts to identify the genes involved in the metastasis are pivotal for the early prediction of oral cancer behavior. However, the identity and time of onset of the alterations that endow cancer cells with these metastatic functions are largely unknown. The process of metastasis consists of sequential and selective steps including proliferation, induction of angiogenesis, detachment, motility, invasion into circulation, aggregation and survival in the circulation, cell arrest in distant capillary beds, and extravasation into organ parenchyma. In this review, we introduce recent findings of the molecular mechanism of oral cancer invasion and metastasis.

We report a case of plasma cell gingivitis (PCG), which is a chronic inflammatory disorder, histologically characterized by dense plasma cell infiltration in the mucosa. The patient was a 55-year-old woman who presented with well-circumscribed redness associated with diffuse edematous swelling of the maxillary and mandibular anterior-tooth gingiva in December 2010. A second biopsy showed dense inflammatory cell infiltration, including mainly plasma cells, with no atypical cells. Immunohistochemically, these cells were positive for immunoglobulin kappa and lambda light chains. On the basis of the clinical and histopathological findings, the lesion was diagnosed as PCG. The patient was treated with a topical steroid containing antibiotics, and the lesion disappeared 6 months after starting treatment. No recurrence has occurred during 3 years of follow-up.

Extrapharyngeal foreign bodies buried under the mucosa are considered uncommon, and early extraction is desirable. We report our experience with the case of a migrated fish bone between the medial and lateral pterygoid muscles.

　The patient was a 65 year-old man who had severe pain after eating monkfish. Intraoral examination revealed redness and swelling of the soft palate at the posterior of the right maxillary tuberosity. Computed tomographic (CT) examination showed punctiform nonradiolucent findings on axial sections and linear nonradiolucent findings on saggital sections between the medial and lateral pterygoid muscles. The fish bone was extracted with the patient under general anesthesia. We were able to identify the fish bone relatively easily on three-dimensional CT images.

　Because an extrapharyngeal foreign body can cause lethal conditions due to secondary infection, it was necessary for us to enucleate it immediately. However, an intraoperative unprepared search can cause harmful phenomena such as vascular damage. Therefore, determining the location by CT was useful for the early and safe extraction of the foreign object.

A diverticulum is a sac-shaped protrusion of a part of the digestive tract. Its occurrence in the buccal mucosa, as seen in the present case, is quite rare. Because it differed from a diverticulum in the digestive tract, the final diagnosis was a diverticulum-like lesion.

　We recently treated a 72-year-old man presenting with a lesion similar to a buccal mucosa diverticulum. This case is outlined and discussed with reference to the relevant literature. When the oral cavity was examined, a bag-shaped depression, 5 mm in diameter, was seen 10 mm below the parotid papilla. The mucosal surface of the inner wall was smooth, normal in color, elastic-soft, and formed a small bag-shaped depression. Based on a clinical diagnosis of a diverticulum-like lesion of the buccal mucosa, the affected area was resected with the patient under local anesthesia. The resected tissue was pathologically evaluated to be a pseudodiverticulum. The mucosa lining the inner surface of the resected tissue was comprised of parakeratotic and hypertrophic stratified squamous epithelium, and inflammatory cell infiltration (primarily by lymphocytes) was seen in the subepithelial area. The affected mucosa was partially depressed, and the muscular tissue immediately below the lesion was defective, but muscular tissue was partially seen in the surrounding area. To date, more than 3 years since the surgery, no abnormalities or signs of recurrence have been detected.

The prevalence of supernumerary teeth is about 1%, and cases of multiple supernumerary teeth are extremely rare. In addition, supernumerary teeth are often found in the anterior maxillary region, but rarely occur in the molar region. We report a rare case of 3 impacted supernumerary teeth in the maxillary third molar region that occurred in a 16-year-old boy who do not have any genetic disorder. Panoramic X-ray films and computed tomography showed 3 supernumerary teeth impacted in the third molar region of right maxilla. All were extracted during a single surgical procedure with the patient under general anesthesia. Each of the supernumerary teeth was found to be incompletely developed, while they were similar to normal permanent molars in both shape and size. The postoperative course was satisfactory, and we are continuing periodic follow-up examinations of the patient.