First presentation of a frameshift mutation in the SETD2 gene of a juvenile psammomatoid ossifying fibroma (JPOF) associated with an aneurysmal bone cyst.

BACKGROUND: The rarity of juvenile psammomatoid ossifying fibroma (JPOF) and lack of cytogenetic studies prompted us to report a novel SETD2 gene mutation in a benign odontogenic tumour. CASE PRESENTATION: A 21-year-old man presented with a hard, expanded mandibular cortex. Computed tomography revealed multilocular radiopacity in the mandible; this was reconstructed via segmental mandibulectomy using a vascularised iliac crest flap. Based on the clinical and histological findings, we diagnosed JPOF associated with an aneurysmal bone cyst. Microscopically, the solid area was characterised by many rounded or angular ossicles in a cellular fibrous stroma. The stromal cells were spindle-like or stellate. Next-generation sequencing detected a frame shift mutation of the SETD2 gene, while the copy number was normal. CONCLUSIONS: Our findings suggest further genetic studies should be performed to assess whether this mutation is related to tumour genesis. .