Malignant osteoblastoma versus osteosarcoma: a case report.

A 33-year-old male developed a slow-growing mass at the anterior aspect of the left tibia for 8 months. The radiologic finding revealed a well-circumscribed osteolytic mass and appeared benign to most radiologists. The lesion was then excised locally. The histology revealed bizarre osteoblasts and osteoclast-like giant cells interspersing in the vascularized stroma and trabeculated osteoids; the periphery of the lesion showed sclerotic mature bones. Malignant osteoblastoma was, therefore, entertained and the patient was treated as such without aggressive surgery and chemotherapy. He has survived for 11 years. However, the diagnosis of malignant osteoblastoma was still a contradiction because of the presence of cartilage foci.