A extremely rare bone tumor characterized by abundant collagen formation and a fibrous stroma, without evidence of mitosis or pleomorphism. It appears on x-rays as an osteolytic lesion with well-defined margins and must be differentiated from primary fibrosarcoma of bone. (DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p1441). The disease is EFO_1001783 (desmoplastic fibroma). Also known as: Fibroma, Desmoplastic.