Hybrid Central Odontogenic Fibroma with Giant Cell Granuloma like Lesion: A Report of Three Additional Cases and Review of the Literature.

Central odontogenic fibroma (COF) is an uncommon intraosseous neoplasm of the gnathic bones which is composed of fibrous connective tissue, with or without calcifications, and variable amounts of inactive odontogenic epithelium. It makes up less than 5% of odontogenic tumors and is more commonly seen in females. Central giant cell granuloma (CGCG) is a locally destructive but benign lesion of the jaws containing osteoclast-like multinucleated giant cells in a fibrovascular stroma. CGCG makes up approximately 10% of all benign jaw tumors and typically occurs in females younger than 30 years of age. A hybrid lesion with histologic features of both COF and CGCG is very rare and was first described in 1992. To date, fewer than 50 cases of this lesion have been reported. In this study, we present three additional cases of COF developing in conjunction with giant cell granuloma-like lesion, as well as provide a comprehensive literature review. Two of the lesions presented in our study were located in the posterior mandible and one occurred in the anterior mandible. Buccal and/or lingual expansion was noted in two patients and no recurrence was reported. Histologically, all three lesions demonstrated a blend of odontogenic epithelial islands with numerous multinucleated giant cells in a highly cellular connective tissue stroma. Immunohistochemical staining with CK19 and CD68 highlighted the odontogenic epithelium and multinucleated giant cells respectively. The precise nature of these hybrid lesions remains obscure and additional molecular studies may be of help in understanding their pathogenesis.