Thirty-five T1 squamous cell carcinomas of the oral cavity underwent clinical and histopathological investigation and the results were as follows: 1) Recurrence was not observed in tumors which were resected with more than 1 cm of surgical safe margin (SSM), and 10 of 25 tumors which were resected with less than 1 cm of SSM revealed recurrence. 2) The mode of epithelial dysplasia around invasive carcinoma was classified into 3 types. Compared to tumors with type I dysplasia (localized mild dysplasia around the invasive carcinoma), those with type II (widely spreading severe dysplasia) and type III dysplasia (multifocal severe dysplasia with multifocal invasive carcinomas) recurred more often. 3) Lymph node metastasis was observed in one tumor before treatment and late metastasis occurred in 5 patients in whom 3 tumors were grade 3 in mode of tumor cell invasion. These results indicated that T1 tumor should be resected with more than 1 cm of SSM and late lymph node metastasis tends to occur in T1 tumors, especially in those exhibiting grade 3 invasion mode, and that oral multifocal dysplasia may result in multicentric carcinogenesis.

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Membrane type-matrix metalloproteinase (MT-MMP) has been recently cloned as an activator of MMP-2 (gelatinase A) . The expression of MT-MMP in human lung and gastric carcinomas has been found to correlate well with the activation of MMP-2, suggesting that the MMP-2 activation by MTMMP is a key step in cancer invasion and metastasis. The purpose of this study was to examine the expression of MT-MMP and its correlation with cancer invasion and metastasis in human oral squamous cell carcinoma (HOSCC) . Expression of MT1-MMP, MT3-MMP, and MMP-2 was examined by immunohistochemistry in 33 cases of HOSCC in relation to mode of cancer invasion and presence/absence of lymph node metastasis. Expression of MT1-MMP in the carcinoma cells was detected in 18 cases (54.5%), MT3-MMP in 18 cases (54.5%), and MMP-2 in 15 cases (45.5%) . MT1-MMP was co-localized in the carcinoma cells in almost all MMP-2 positive cases (14/15 cases) . As the mode of invasion increased from grade 1 to grade 4 D, the ratio of positive cases of MT1-MMP, MT3-MMP, and MMP-2 tended to increase, and the majority of diffusely invasive carcinomas (grade 4C and 4D) co-expressed MT1-MMP and MMP-2 (8/9 cases) . Carcinomas with lymph node metastasis also showed a high frequency of expression of MT1-MMP, MT3-MMP, and MMP-2. These results suggested that MT1-and MT3-MMPs co-expressed with MMP-2 may play an important role in cancer invasion and metastasis of HOSCC.

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Of children aged 15 or younger who visited the Second Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Iwate Medical University between April 1975 and March 1995, 59 children with tumor of the oral and maxillofacial regions in whom histopathology provided definitive diagnosis were clinically examined. There were 57 patients (57/59 : 96.6%) with benign tumor and 2 patients (2 /59 : 3.4%) with malignant tumor. Thirteen (13/57: 22.8 %) of the 57 patients with benign tumor had soft tissue tumor. Angioma was most frequently observed. Forty-four (44/57 : 77.2%) of the 57 patients had bone tumor. Odontoma was most frequently observed. Concerning site, soft tissue tumor commonly developed in the lip, tongue or buccal mucosa. Bone tumor commonly developed in the mandible. There was no gender difference. The incidence of bone tumor was slightly increased in children over 6 years old. In Particular, the incidence of odontogenic tumor was increased, of the 57 patients with benign tumor, surgical treatment was indicated, and the course was good in all patients. Of the 2 patients with malignant tumor, the postoperative course was good in one patient with chondrosarcoma. However, in the other patient with Ewing's sarcoma, combination therapy with surgery, radiotherapy and chemotherapy was performed, but the patient died.

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Harmonic scalpel^® (HS), an ultrasonic vibrating scalpel, was used during oral and maxillofacial surgery. Mechanical vibration with a frequency of 55, 500Hz allows dissection and coagulation. By using HS, the number of vessel legations could be reduced and reliable hemostasis could be obtained. It is thought that HS will become popular as an essential instrument for oral and maxillofacial surgery in the near future.

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A case of large compound odontoma of the mandibular body is reported.
A 14-year-old female complained of a asymmetric diffuse swelling in the mandibular body. Intraoral examination revealed expansion of the buccal plate in the area of the left mandibular body, and absence of second and third molars. A panoramic radiograph showed large, circumscribed, radiopaque lesion surrounded by a thin radiolucent area. Axial computerized tomography showed a welldefined radiopaque mass eroding the buccal and lingual cortex of the mandible.
Under general anesthesia, the tumor was enucleated by an intraoral approach. Intraoral incision extending from the mesial aspect of the mandibular to the external oblique line of the ramus was performed. A subperiosteal dissection exposed the buccal plate of the mandibular body. Through an occlusal buccal window, the lesion was exposed and enucleated. The cavity was filled with cancellous bone marrow grafted from the iliac crest, the buccal plate was displaced with a reconstruction plate, and the wound primarily closed. The sensation in the distribution of the inferior alveolar nerve was preserved.
The tumor was diagnosed as a compound odontoma by histological examination. In the surrounding soft tissue, odontogenic epitheliums were observed. Patients must be followed up for a long time and local recurrences must be controlled.

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A 42-year-old female was referred to our clinic in July 1993 for treatment of gradually increasing bilateral swelling in the parotid gland region, which began three years ago, together with excessive dryness of the mouth. Bilateral diffused swelling was observed in the parotid gland areas, and palpation revealed a relatively well-defined, elastic walnut-sized mass on the left side, as well as two similar masses on the right side. Clinical findings, including imaging diagnosis, were unclear. An excisional biopsy was performed through superficial ablative surgery on the left parotid gland area, and the same surgery was perfomed on the right side two months later. The histopathological diagnoses in both cases were benign lymphoepithelial lesions.
During the year following surgery, a bean-sized mass gradually became detectable in the left parotid gland area. An excisional biopsy of the mass was performed in February 1995, and the histopathological diagnosis was diffuse, medium-sized cell malignant lymphoma. The patients was treated with chemotherapy at the Department of Internal Medicine, Nihon University Surugadai Hospital, receiving five CHOP and four MEC-2 treatments, and follow-up observation was continued through 1997.
A CD20 positive result for the Pan B cell marker was observed, as well as a CD 3 negative result for the T-cell marker. Therefore, the tentative diagnosis was a MALT-type lymphoma as the basis of a lymphoepithelial lesion of the parotid gland.

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A rare case of bilateral maxillary sinus squamous cell carcinoma manifested in the left side 6 years after successful treatment of the first lesion on the right side is presented. Management of both tumors consisted of a combination of chemotherapy, irradiation and surgery. Treatment of the second cancer was unsuccessful.
This report emphasizes the need for critical and long-term follow-up for cancer patients.

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