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.1 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.2 Radiographically, they typically appear
destructive and radiolucent, often resembling the radiographic
appearance of aneurysmal bone cysts.3 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,4 can be
seen in association with telangiectatic osteosarcomas and are
thought to represent areas of hemorrhage into cystic
spaces,5 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.6 The prognosis is considered to be similar
to that of conventional osteosarcomas.
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.
1. Whitehead RE, Melhem ER, Kasznica J, et al. Telangiectatic
osteosarcoma of the skull base. Am J Neuroradiol.
2. Klein MJ, Kenan S, Lewis MM. Osteosarcoma: Clinical and
pathological considerations. Orthop Clin North Am.
3. Kyriakos M, Hardy D. Malignant transformation of aneurismal
bone cyst, with an analysis of the literature. Cancer.
4. Hudson TM. Fluid levels in aneurysmal bone cysts: A CT
feature. AJR Am J Roentgenol. 1984;142:1001-1004.
5. Tsai JC, Murray KD, Fallon MD, et al. Fluid-fluid level: A
nonspecific finding in tumors of bone and soft-tissue.
6. Bacci G, Ferrari S, Ruggieri P, et al. Telangiectatic
osteosarcoma of the extremity. Acta Orthop Scand.
Prepared by Justin Q. Ly, MD and
Douglas P. Beall, MD from the Department of
Radiology and Nuclear Medicine, Wilford Hall Medical Center, San