Cemento-ossifying fibroma (COF) is classified as a fibro-osseous lesion and usually presents as a progressively growing lesion that can reach a large size if left untreated. Fibrous dysplasia (FD) is a non-neoplastic development that affects the craniofacial bones and is characterized by painless hypertrophy due to the replacement of bone by abnormal fibrous tissue. Herein, a case of concurrent occurrence of COF and FD involving the right mandible is described in a 14-year-old male patient. In this review, the current knowledge of FD and COF is summarized, emphasizing the importance of integrating the understanding of clinical, radiographic, and histopathological features. In addition, the relevant aspects associated with differential diagnosis and patient care are evaluated.

Cemento-ossifying fibroma is a benign fibrous lesion with an unknown cause, mostly asymptomatic, painless swelling of the affected jaw. This is a case report on a cystic lesion found on radiographic examination in a patient with an extraction of mandibular left tooth. A 29-year-old female was referred to Pusan National University Dental Hospital due to a radiopaque lesion in the left mandible. On the medical history examination, the left lower mandibular tooth had been extracted 4 years ago, and there were no specific findings in the general medical history. According to histopathologic findings, along with proliferation of spindle cells, cementum-like substances were observed along with irregularly shaped osseous calcified substances containing osteocytes in the cellular fibrous connective tissue. In this study, we report a case that showed cystic changes due to tooth extraction, which made it complicated to determine the differential diagnosis from the existing fibrous-osseous lesion.

A 31 years old female had been suffered from a bony swelling in right premolar region of the mandible for 12 years, recently grown rapidly. A fistula tract developed on the right anterior mandibular border, but the lesion was relatively asymptomatic. In the radiological examination, the tumor mass was irregularly mixed with radiolucent and radiopaque areas, forming multiple cystic spaces. Under the diagnosis of calcifying odontogenic cyst, the mandibular mass was resected and examined pathologically. After decalcification, the dissected tumor mass showed multiple small cystic spaces and calcifying fibrous tissue, mimicking calcifying odontogenic cyst or ameloblastoma. Histological observation showed many calcifying cementoid materials and ossifying trabeculae. The cystic spaces were turned out to be dilated vascular channels lined by endothelial cells, containing plasma fluid. However, the main lesion was diagnosed as cemento-ossifying fibroma (COF), and the atypical vascular channels were greatly dilated and gradually expanded the whole tumor mass. The present COF was examined through immunohistochemical (IHC) array, and investigated for tumor cell characteristics, exhibiting abnormal ossification and aneurysmal cystic changes. IHC array disclosed that the tumor cells grew progressively in the lack of apoptosis, and that they showed lower expression of RUNX2 than BMP-2, RANKL, and OPG, and increases of protein expression in HIF-1α, VEGF-A, and CMG2. These data suggested that the reduced expression of RUNX2, osteoblast differentiation factor, be relevant to abnormal ossification of COF, and that the consistent expressions of angiogenesis factors be relevant to de novo angiogenesis in COF, subsequently resulted in aneurysmal cystic changes.