The anteroposterior radiograph of the pelvis shows a lytic,
expansile lesion of the right acetabulum that extends into the
ilium and superior pubic ramus with cortical breakthrough of the
iliopubic line. There are coarse calcifications in the center of
the lesion that represent the chondroid matrix, which is frequently
a characteristic of chondroid tumors. Surgical fixation hardware is
present from a remote traumatic acetabulum fracture (Figure 1).
CT images reveal a large heterogeneous mass erupting through the
posterior cortex of the right pubic bone and occupying most of the
right pelvis (Figure 2). Bony destruction and extensive areas of
necrosis within the mass are typical features of these aggressive
Distant metastases were found by CT of the chest and magnetic
resonance (MR) imaging of the cranium. In the chest, there are
multiple bilateral soft tissue lung masses and a large pleural
effusion. These were biopsy-proven dedifferentiated chondrosarcoma
(Figure 3). An axial postgadolinium T1-weighted MR image of the
brain shows multiple ring-enhancing masses that are most consistent
with metastases (Figure 4).
Fine-needle aspiration of the mass (Figure 5) and subsequent
biopsy (Figure 6) resulted in the pathologic diagnosis of
Chondrosarcoma is a tumor that is composed of neoplastic,
mesenchymally derived cartilaginous cells and, other than
osteosarcoma, is the most prevalent myxoid tumor found in the
skeletal system. Dedifferentiated chondrosarcoma occurs in
approximately 11% of patients diagnosed with chondrosarcoma and is
considered to be a histological subtype of this chondroid
The term "dedifferentiated" implies that a
portion of cells from the chondrosarcoma have degenerated into a
high-grade malignant form that is characterized by pleomorphism,
anaplasia, hypercellularity, and increased mitoses.
Dedifferentiated chondrosarcomas typically arise centrally in the
Imaging commonly provides evidence of
both the cartilage tumor and the high-grade noncartilaginous
component. There is usually an abrupt transition between these 2
The cartilaginous component may contain
irregular areas of lysis with endosteal scalloping and periosteal
thickening. These areas may also contain minute foci of
calcifications in a ringlike configuration. The sarcomatous
component is grossly lytic. Lytic lesions may be detected by
cortical perforation and possible extension, which can result in a
Due to its locally invasive nature, high
rates of recurrence, and metastatic seeding of the skeleton and
lungs, dedifferentiated chondrosarcoma carries a grave prognosis.
When the tumor is deemed operable, most patients are treated with
wide-margin resection and adjuvant chemotherapy. Despite this
therapy, most patients die within 1 year of diagnosis.2
Dedifferentiated chondrosarcoma is an aggressive subtype of
chondrosarcoma that is characterized by a cartilaginous component
and a highly lytic sarcomatous component. Radiographically, there
is often an abrupt transition between these tissue types within the
lesion. A core biopsy can be used to help distinguish this tumor
from other, less aggressive tumors and benign bone lesions. These
patients typically present with complaints of bone pain and
restricted movement; their prognosis is poor.
- Frassica FJ, Unni KK, Beabout JW, Sim FH. Dedifferentiated
chondrosarcoma. A report of the clinicopathological features and
treatment of seventy-eight cases. J Bone Joint Surg Am. 1986:68:
- Kilpatrick SE, Pike EJ, Ward WG, Pope TL. Dedifferentiated
chondrosarcoma in patients with multiple osteochondromatosis:
Report of a case and review of the literature. Skeletal Radiol.
- de Lange EE, Pope TL Jr, Fechner RE. Dedifferentiated
chondrosarcoma: Radiographic features. Radiology.
- Mercuri M, Picci P, Campanacci L, Rulli E. Dedifferentiated
chondrosarcoma. Skeletal Radiol. 1995:24:409-416.