A 20-year-old man presented to the clinic with a painful mass in his right knee. He recently had a plain radiographic knee study at another institution that was read as normal.
Justin Q. Ly, MD
Douglas P. Beall, MD
from the Department of Radiology and Nuclear Medicine, Wilford
Hall Medical Center, San Antonio, TX.
A 20-year-old man presented to the clinic with a painful mass in
his right knee. He recently had a plain radiographic knee study at
another institution that was read as normal. At that time, the mass
was noted to be smaller and less painful. A new radiographic knee
study was obtained, followed by futher evaluation with magnetic
resonance (MR) imaging.
The anteroposterior radiograph of the right knee revealed
obliteration of the cortex along the medial femoral metadiaphysis,
associated with an ill-defined lucency involving the distal medial
femur, as well as the epiphysis (Figure 1). Faint osseous matrix
may be seen. No clear periostitis was identified, but there is an
associated, large soft-tissue mass overlying and medial to the
described osseous changes. The MR study confirms the presence of
the large mass and associated cortical destruction (Figure 2).
Additionally, multiple fluid-fluid levels are seen throughout the
mass (Figure 3). There is extension into the intra-articular space
and medial head of the gastrocnemius muscle, and displacement of
the neurovascular bundle.
Osteosarcomas are the most common primary malignancies of bone,
occurring predominantly in the population younger than age 30. They
most frequently involve the ends of long bones, particularly the
distal femur and proximal tibia.
Common clinical presentations include pain, pathologic fracture,
and soft-tissue mass. Telangiectatic osteosarcomas are an uncommon,
yet aggressive, morphologic variant, comprising approximately 2% to
4% of all osteosarcomas.
Radiographically, they typically appear destructive and
radiolucent, often resembling the radiographic appearance of
aneurysmal bone cysts.
Although there is usually only a small amount of osseous matrix
within this neoplasm, it is not unusual for there to be a
significant associated soft-tissue component. Periosteal reaction
in the form of a Codman's triangle may be seen in association with
a more rapid-growing tumor. Fluid-fluid levels on computed
tomography (CT) and MR imaging, although nonspecific findings,
can be seen in association with telangiectatic osteosarcomas and
are thought to represent areas of hemorrhage into cystic spaces,
which are characteristically lined by giant cells and tumor cells
rather than the endothelial cells more typical of aneurysmal bone
cysts. Osteosarcomas, in general, have been known to be metastatic,
with the lungs being the most common site of invasion. The
treatment generally involves wide local excision and, sometimes,
limb amputation, depending on the extent of the disease. Some
believe that there may be a role for chemotherapy.
The prognosis is considered to be similar to that of conventional
The telangiectatic osteosarcoma is an uncommon type of
osteosarcoma characterized by hemorrhage into dilated cystic
spaces, which often results in fluid-fluid levels on CT and MR
imaging. These patients typically present with severe pain, and
care should be taken to distinguish this neoplastic process from
aneurysmal bone cysts and other benign processes that may have a
similar imaging appearance.