β-Human Chorionic Gonadotropin-Secreting Giant Cell Tumor of Bone in the Mandible: Case Report and Comprehensive...

Giant cell tumor of bone (GCTB) is a rare but locally aggressive neoplasm which most commonly arises in the epiphyses of long bones of young adults. Occurrence in the mandible is uncommon, and hormone secreting variants are extremely rare.

We present the case of a 16-year-old female, who presented with progressive swelling and pain in the left mandible after extraction of adjacent teeth. On examination, she had a large ulcerated intraoral mass with marked tooth mobility; imaging revealed a 4.7-cm expansive lytic lesion with cortical erosions and displacement of the inferior alveolar canal. Histopathologic evaluation revealed sheets of mononuclear stromal cells interspersed with numerous osteoclast-like giant cells. Immunohistochemical stains showed strong positivity for H3G34W and p63. Genomic sequencing confirmed the presence of an H3-3A p.G35W hotspot mutation and also identified a pathogenic FANCA p.R951Q variant. Investigations prior to treatment showed an elevated serum β-human chorionic gonadotropin (β-hCG) level despite the patient being negative for pregnancy status. Following this the patient began denosumab therapy, which was associated clinical improvement, plus a decline in β-hCG, confirming the tumor as the source of hormone secretion.

There is only one other case that has been documented of a β-hCG-producing GCTBoccurring in the base of the skull with secondary aneurysmal bone cyst-like changes.This appears to be the first reported instance of β-hCG-secreting GCTB in the gnathicbones. This case exemplifies the diagnostic challenges of rare presentations of GCTBand alerts clinicians to the potential misleading presentation of hormone expression.