A 45-year-old woman with a history of osteoporosis is found to have a lytic lesion in her jaw. A biopsy shows a mixture of giant cells and spindle cells, with hemosiderin deposits and evidence of hemorrhage. Laboratory tests reveal elevated parathyroid hormone levels. Genetic testing shows no significant mutations. Given the findings, what is the most likely cause of the lesion?

A 19-year-old male presents with pain and swelling around the knee. Imaging reveals an epiphyseal lesion with well-defined borders. Histology shows multinucleated giant cells dispersed in a background of polygonal cells with a cartilaginous matrix. Genetic testing reveals an H3F3B mutation. What is the most likely diagnosis?

A 33-year-old male presents with a progressively enlarging mass in his mandible. Imaging shows a multilocular, radiolucent lesion with cortical thinning. Histologically, the lesion contains multinucleated giant cells with spindle-shaped stromal cells and areas of hemorrhage. Laboratory tests reveal normal calcium levels and no systemic abnormalities. Which diagnosis is most likely?

A 23-year-old male presents with localized pain and swelling in his distal radius. Imaging reveals a well-demarcated, lytic lesion in the metaphysis with cortical thinning but no periosteal reaction. Histologically, the lesion contains numerous multinucleated giant cells in a background of fibroblasts, but no cellular atypia is seen. Genetic testing shows a USP6 gene rearrangement. What is the most likely diagnosis?

A 30-year-old female presents with a painful, progressively enlarging mass in the distal femur. Imaging reveals an expansile, lytic lesion involving the epiphysis with cortical thinning. A biopsy shows multinucleated giant cells uniformly scattered among mononuclear stromal cells, and the tumor is found to have an H3F3A mutation. Which of the following would most likely be observed on further investigation?