Osteoblastoma

Conventional osteoblastomas are composed of a well-vascularized connective tissue stroma in which active production of osteoid and primitive woven bone occurs. The most common locations are the flat bones or vertebrae, although the long tubular bones may also be involved, predominantly in the diaphysis. On radiographs, a nondiagnostic picture consisting of osteolysis alone, osteosclerosis alone, or a combination of both osteolysis and osteosclerosis may be observed. Additional findings may include expansion of bone, cortical thinning, and a soft tissue mass. In the spine, a well-defined, expansile osteolytic lesion arising from the posterior osseous elements may be noted. Scoliosis may also accompany spinal or rib osteoblastomas.

Bone scans, CT scanning and MR imaging are helpful in diagnosis. However, an inflammatory reaction in the nearby soft tissues may simulate the appearance of a malignant tumour on MR images.

Aggressive osteoblastomas tend to occur in the same sites as their benign counterparts, and the radiological features of these lesions resemble those of typical osteoblastoma but with a greater likelihood of soft tissue involvement. Differentiating these osteoblastomas from osteosarcoma may be difficult.

DR