A CLINICOPATHOLOGIC STUDY OF 144 ORTHOKERATINIZED ODONTOGENIC CYSTS

Background Orthokeratinized odontogenic cysts (OOCs) are uncommon intraosseous cystic lesions and are distinguished as an individual entity of odontogenic cysts in the new World Health Organization classification. Objective To analyze the clinicopathologic features of OOC in a Chinese population. Methods All cases reported as OOCs and odontogenic keratocysts (OKCs) were reviewed from the files of the Department of Oral Pathology, Peking University School and Hospital of Stomatology, from 2000 to 2018. We identified 144 OOC cases and analyzed clinical and pathological information. Results In the present study, we report the largest series of OOC cases, to our knowledge. There were 98 male and 46 female patients with a peak incidence in the third to fourth decades of life. One hundred thirty-six cases (94.4%) were solitary, and 8 cases (5.6%) were multiple. The most common sites were in the mandibular molar and ramus region. Radiographically, 12 lesions showed multilocular radiolucency with bone destruction, whereas others were unilocular. All the cases were primary. In follow-up of 116 patients, 114 were treated by simple enucleation, which revealed no recurrence over a period of 0.5-17 years after surgery. Compared with OKCs, OOCs revealed different histologic and immunohistochemical features. Conclusions OOC is clinicopathologically distinct from OKC and should constitute its own clinical entity according to histologic features and biologic behavior. Further study is needed to investigate the pathogenesis and mechanism of OOCs.