Keratin Positive Giant Cell Rich Tumor of the Pelvic Bone with a HMGA2::NCOR2 Fusion: A Case Report.

Keratin positive giant cell rich tumor is a rare mesenchymal tumor first described in 2020. It can occur in both soft tissue and bone and predominantly affects young women. The tumor's biological behavior remains uncertain despite its low-grade classification. Characterized by keratin expression and a HMGA2::NCOR2 gene fusion, keratin positive giant cell rich tumors resemble conventional giant cell tumors but lacks H3-3A gene mutations. This article presents a 31-year-old woman with a keratin positive giant cell rich tumor in the pelvic bone, detailing her clinical presentation, diagnostic process, treatment, and postoperative recovery. Histological examination revealed numerous osteoclast-like giant cells within a mononuclear stroma, with RNA sequencing confirming the HMGA2::NCOR2 fusion. The patient's management included surgical resection, with no recurrence at six months follow-up. The discussion emphasizes the need for further research to understand keratin positive giant cell rich tumors pathogenesis and explore potential targeted therapies.