Abstract
Parosteal osteosarcoma is a low-grade osteosarcoma, which occurs on the surface
of the bone. We had experienced a parosteal osteosarcoma involving the flat
bone, the scapula of a 21-year-old man. This is an extremely rare location for a
parosteal osteosarcoma. Plain radiograph showed broad-based, well-defined
radiodense lesion at the scapula. Computed tomogram demonstrated an intact
cortex and absence of a medullary involvement. Tumor showed a lobulated,
high-density lesion, indicating bone formation. Histologically, parosteal
osteosarcoma is a well-differentiated osteosarcoma. The tumor is composed of a
hypocellular proliferation of spindle cells, with minimal cytologic atypia. The
bone is in the form of a well-formed bony trabeculae. Occasional cartilage is
present in the form of a cap.