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Clinicopathological studies and flow cytometric analyses were performed for 62 cases of odontogenic keratocyst obtained from the file of the Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry between 1984 and 1998. The Patients ranged in age from 12 to 74 years, and the peak incidence was in the third decade. The male: female ratio was 1.5: 1. Cysts were most frequently found in the third molar region, including the ramus. Most cysts were found incidentally on radiographic examination and appeared as unilocular, smooth bordered, radiolucent lesions. Most lesions were less than 4cm in diameter. Impacted teeth were found in 24 of 70 cysts, and 18.6% of the cysts were associated with root resorption of neighboring teeth. When classified according to the keratin type of the cyst-wall epithelium, most cysts were type II (58.5%).Flow cytometric analysis was performed for lining epithelial cells isolated from paraffin embedded specimens. Nuclear staining was done with Ki-67 antibody. The Ki-67 antigen labeling rate of odontogenic keratocysts was significantly higher (7.9±5.7%) than that of radicular cysts (2.9±1.3%). The number of cysts with a high Ki-67 antigen labeling rate was higher in type III than in the other three groups. We found a significant correlation between the Ki-67 antigen labeling rate on flow cytometry and the Ki-67 antigen positive cell rate on immunohistochemical examination. An advantage of flow cytometric analysis is that it can precisely enumerate proliferating cells of odontogenic keratocysts.

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.

We reported here a case of Lymphoepithelial cyst arising at the ventral surface of the tongue in a 34 year old male.Histopathological examination revealed that the cyst was composed of fibrous tissue, thin squamous epithelium and lymphoid tissue with a prominent germinal center. This case was considered to be a typical, oral lymphoepithelial cyst.We also examined the distribution of immunoglobulins, T and B cells and lysozyme.Immunohistological examination revealed that immunoglobulin-positive cells (IgG, IgA and IgM) were distributed between the lining epithelium and lymphoid tissue with a variation in number. Localization of lysozyme-positive cells was similar to that of immunoglobulin-positive cells. Similar to tonsil and lymph node, B cells were observed in the cap area and medulla of lymphoid tissue while decreased numbers of T cells were found in fibrous connective tissue beneath the lining epithelium.

Spindle cell carcinoma is considered a subtype of squamous cell carcinoma that has a sarcomatoid appearance. In the head and neck region, cases of spindle cell carcinoma of the larynx have occasionally been reported. However, spindle cell cacrcinoma of the maxillary sinus is extremely rare. We describe a case of spindle cell carcinoma of the maxillary sinus in a 53-year-old woman. Surgical treatment was performed under the clinical diagnosis of a maxillary neoplasm. During the operation, a biopsy specimen was taken, and the histopathological diagnosis was a spindle cell carcinoma. The lesion was removed under general anesthesia. Radiotherapy and chemotherapy were additionally given to prevent recurrence and metastasis of the tumor.There has been no evidence of recurrence as of 5 years 6 months after surgrey.

From 1970 to 1996, 129 cases of intraoral minor salivary gland tumors were diagnosed at the Department of Pathology, Nihon University School of Dentistry. The diagnosis of each case was based on the 1991 WHO classification. Eighty benign and 49 malignant minor salivary gland tumors were found in the approximately 9,300 oral biopsies submitted during the 27-year period. Pleomorphic adenomas were the most commonly histologic type of the benign tumors identified and 51% of the malignant tumors were diagnosed as mucoepidermoid carcinoma. The most common primary location of the tumors was the palate. Sixty percent of all tumors occurred in females and the peak age for incidences of all tumors was found in the third, fourth, sixth and seventh decades. These results were compared with those of the studies in different world population groups.

We have described two cases of ossifying fibroma in this paper.The first one was a recurrent case which occurred in a 52 year-old male patient. Tumor masses were found in the lower rim of mandible and in scar tissue close to previously operated areas. Histopthological examination revealed that tumor masses were composed of a proliferation of spherical and trabecular bones and dense fibrous tissue with a high cellularity.The second one was a case observed in a 26 year-old female patient. Histopathological examination revealed that the majority of tumors consisted of a proliferated fibrous tissue and a few immature fibrous bony tissues that were scattered at the peripheral region of this fibrous tissue.Although the enucleation of tumor or marginal resection of mandible were recommended for the treatment of ossifying fibroma, more extensive continuous resection of mandible should be applied to the cases which small tumor nests were scattered throughout the mandible such as case 1.