MACROSCOPIC DESCRIPTION: "Spinal lesion": An aggregate of hard brown and white bony fragments 50 x 40 x 20 mm.

MICROSCOPIC DESCRIPTION: Sections show an irregularly shaped but circumscribed lesion with surrounding normal lamellar bone. The lesion consists of irregular, haphazardly arranged, evenly spaced spicules of osteoid lined by plump but uniform mononuclear osteoblasts and some osteoclasts. Mitoses are not identified. The space between the osteoid is filled with loose connective tissue with prominent blood vessels. There is a little cartilage attached to normal bone, but there is not cartilaginous differentiation within the lesion. Margins cannot be assessed. There is no evidence of malignancy.

DIAGNOSIS: Spinal lesion: Osteoblastoma.