下顎歯肉に発生したｓｑｕａｍｏｕｓ ｏｄｏｎｔｏｇｅｎｉｃ ｔｕｍｏｒの１例

Abstract

We encountered and reported a case of squamous odontogenic tumor that developed in the gingiva of the lower third molar of a 51-ear old woman. This case may be the first of this kind of tumor ever reported in Japan. The chief complaints were gingival bleeding and painless swelling. The tumor was nodular, firm and located distal to the gingiva of the lower third molar. It was a tumor in size of the tip of the small finger, presenting the color of healthy gingiva. Radiographically, a horizontal type bone absorption was noted around the molar. As for the treatment, extraction of the molar and local excision of the tumor were performed. Histologically, numerous islands large and small consisting of well differentiated squamous epithelium were observed. The stroma was composed of mature fibrous collagenous connective tissue. The periphery of the islands was flattened or cuboidal but mostly flattened and showed no epithelial columnar cells. The presence of vacuolization and/or microcyst formation was observed in the islands and acidophilic substances were found in the microcyst formation. Prognostic observations were made for two years and six months during which no recurrence was noted. As to the development of this tumor, a theory that it is derived from Malassez epithelial remnant is widely accepted. However, we have presented a view againt this theory. In our view, it is possible that a weak dental lamina of the permanent teeth or the lateral enamel strand prior to formation of ameloblast remains in the jaw bone and/or paradentium and later developes into a tumor.