Central giant cell granuloma of the mandible: presentation of a rare case with prominent osteoblastic differentiation mimicking osteosarcoma

Abstract

Central giant cell granuloma (CGCG) is a non-neoplastic proliferative lesion of unknown etiology. A wide variety of conditions could be misdiagnosed with CGCG, both histopathologically and radiographically. We report a rare case involving a 40-year-old female with CGCG of the mandible and prominent osteoblastic differentiation unlike that of conventional CGCG common to osteosarcoma. The patient presented with a painless swelling in the area between the lower left canine to the lower first molar. The lesion was surgically removed under general anesthesia, and the surgical specimen was investigated histopathologically and immunohistochemically. In this lesion, multinucleated giant cells were dispersed among a highly cellular stroma consisting of mononuclear round and spindle-shaped cells. Mononuclear cells demonstrated cellular pleomorphism and high proliferative activity, as evidenced by Ki-67 immunostaining. Immature osteoid was seen throughout the lesion, and most mononuclear cells exhibited Runx2 positivity. Despite these histopathological features in common with those of osteosarcoma, the lesion was shown radiographically to be well-defined and without infiltration of the surrounding bone, and a 3-year follow-up of the patient has thus far been uneventful. The lesion was diagnosed as a rare CGCG with prominent osteoblastic differentiation mimicking osteosarcoma.