Assessment of MDM2 Gene Locus Amplification by Fluorescence In-Situ Hybridization in Juvenile Ossifying Fibroma

Juvenile ossifying fibroma (JOF) is an uncommon benign fibro-osseous lesion (BFOL) of the maxillofacial bones with a locally aggressive nature and a high recurrence rate. Murine Double Minute 2 (MDM2) is an oncogene located at chromosome 12 (12q13-15) that inhibits the tumor suppressor gene TP53. The presence of MDM2 gene locus amplification is a useful molecular adjunct in the evaluation of some sarcomas, including low-grade intramedullary osteosarcoma (LGIOS). JOF and LGIOS have some overlapping clinical and histopathological features. The aim of this study is to evaluate a series of JOF for the presence of MDM2 gene locus amplification using fluorescence in-situ hybridization (FISH).

With IRB approval, a search of the institutional files of the archives of the Oral Pathology and Surgical Pathology biopsy services at the University of Florida Health was performed. The cases were re-evaluated by an oral pathology resident, an oral and maxillofacial pathologist, and a bone and soft tissue pathologist. Cases with consensus in diagnosis were selected (n = 9) for MDM2 testing. Testing by FISH for MDM2 gene locus amplification was applied to all retrieved cases.

The examined cases were all negative for MDM2 gene locus amplification via FISH testing.

In our small series, JOF did not demonstrate MDM2 gene locus abnormality, a characteristic of LGIOS. This finding suggests that JOF has a distinct underlying pathogenesis. If confirmed in a larger series, these findings may be useful in distinguishing these two entities in cases with overlapping features or when minimal biopsy material is available.