The lower end of the femur is involved by a medullary, cystic and solid, focally sclerosed, metaphyseal-diaphyseal tumor which breaks through the cortex, but does not transgress the epiphyseal cartilage. The upper margin is 9 cm from the severed end. It is characterized by large blood-filled cystic cavities and septations. Telangiectatic osteosarcoma arises within the diaphysis with frequent extension into the metaphysis. The tumor is frequently entirely osteolytic with geographic bone destruction.
Periosteal reaction is present in most patients.
Fluid-fluid levels secondary to this hemorrhagic process may also be seen. The septations may enhance after gadolinium administration. Telangiectatic osteosarcoma is a characteristic morphological subtype of conventional, central osteosarcoma that tends to be highly chemosensitive. Large blood-filled cavities with delicate septations simulate aneurysmal bone cyst morphology. Osteoid production is usually scant, which explains the lytic radiological features.