Mural squamous odontogenic tumor in a primordial cyst.

An additional case of mural squamous odontogenic tumor in a mandibular primordial cyst is reported and its clinicopathologic features are described. Introduction Since Pullon et al.[1] reported 6 cases of a previously undescribed lesion under the name squamous odontogenic tumor (SOT) in 1975, SOT has been accepted as a distinct entity among odontogenic tumors [2,3]. Histologically identical lesions have been noted adjacent to the lining of several odontogenic cysts [4-11]. We report an additional case of mural SOT in the wall of a mandibular primordial cyst. Case report A 19-year-old man was referred by his dentist to the oral surgery clinic at Saitama Medical Center in October, 1986, because of painless swelling in the right maxilla. Intraoral examination showed a fluctuant tender swelling in the right second molar region. Radiographic studies showed a large unilocular radiolucent lesion containing an impacted second molar. Moreover, another sharply defined radiolucent lesion was noted in the third molar region of the left mandible (Fig. 1). The clinical diagnosis was multiple jaw cysts. The patient was given general anesthesia and cystectomy was performed. The healing was uneventful, and there has been no evidence of recurrence for 8 years since the operation. Histologically, the lesion in the right maxilla consisted of pieces of connective tissue lined by thin parakeratinized stratified squamous epithelium lacking rete ridges. The lumen was filled with keratinous material. A diagnosis of odontogenic keratocyst was made. The wall of the cyst from the left mandible was covered by irregular, proliferating nonkeratinized stratified squamous epithelium, and a mild to moderate inflammatory reaction was seen in the thickened fibrous capsule. Deeper in the subepithelial tissue, mural proliferation of well-differentiated squamous epithelial islands was noted (Fig. 2). These squamous islands showed no atypia and lacked the columnar cells that are typical of ameloblastoma. There were microscopic foci of central cystic degeneration and irregular calcified masses surrounded by mature keratin within the tumor islands (Fig. 3).The entire tissue block was serially sectioned, but no continuity with the lining epithelium was found. The present case met the diagnostic criteria for SOT[2,3] and thus a histologic diagnosis of a mural SOT in a primordial cyst was made. Discussion SOT is a benign but locally infiltrative epithelial tumor thought to arise from the rests of Malassez in the periodontal ligament[2,3]. Clinically the lesion occurs over a wide age range. There is no sex predilection, the maxilla and mandible are equally affected, and in some cases the lesion is multicentric. Most cases have shown unilocular radiolucency surrounding the tooth roots. Recurrence seems to be rare after conser下山哲夫、堀江憲夫、金子貴広、鈴木円、種林康彦、小澤俊文、井出文雄 Department of Oral Surgery, Saitama Medical Center, Saitama Medical School To whom all correspondence should be addressed: Dr. Norio Horie, Department of Oral Surgery, Saitama Medical Center, Saitama Medical School, 1981 Kamoda, Kawagoe, Saitama 350, JAPAN.