Chondrosarcoma

Matthew P Schenker, MD - Case Coordinator
Sidney Uttam Jain, MD - Radiology Discussion
David W Kindelberger, MD - Pathology Discussion
Pablo R Ros, MD, MPH - Attending Radiologist
Steven E Seltzer, MD - Attending Radiologist

March 24, 2003

Presentation

Imaging Findings

Axial CT images (soft tissue and bone windows) show a large, hypodense lesion involving multiple muscle groups. Some calcification is evident. Sclerosis and periosteal reaction extend to the knee joint. It seems that there is some resorption of trabeculae in the distal femur.

STIR images show a multilobulated, T2-hyperintense lesion with diffuse medullary edema of the distal femur. No cortical breakdown is apparent on MR. Pre- and post-contrast MR images show diffuse enhancement of the lesion. Displacement of normal fat in the marrow is visible, as is some enhancement of the marrow. Areas of necrosis cross the muscle plane.

Differential Diagnosis

Diagnosis

Discussion

The gross specimen is a 25-cm section of distal femur with attached skeletal muscle and some synovial soft tissue. Bluish-white areas infiltrate the soft tissue. These areas have a myxoid, glistening appearance. Extensive areas of hemorrhage and necrosis are also present. Low-powered microscopy of the myxoid areas shows a relatively monomorphic population of cells with bland nuclear features in a pink chondromixomatous background. At higher power, some degree of nuclear pleomorphism is evident, and occasional nucleoli are present. There is no mitotic activity, however.

Radiology Discussion:

Chondrosarcoma is one of a number of cartilagenous tumors. There are seven types: intramedullary, periosteal/juxtacortical, clear cell, mesenchymal, myxoid, dedifferentiated, and extraskeletal. Chondrosarcoma can arise secondary to enchondroma (Ollier’s/Maffucci), osteochondroma (hereditary multiple exostoses), or Paget’s disease, or can be induced by radiation. The differential diagnosis for cartilaginous tumors also includes osteochondroma (exostoses), chondroma/enchondroma, chondroblastoma, and chondromyxoid fibroma.

Intramedullary chondrosarcoma is the most common type. It occurs more frequently in men than women (average age: 45 years), often in the metaphysis of the femur. Other typical locations include the pelvis, shoulder, ribs/sternum, vertebrae, and scapula. Symptoms generally include pain and a palpable mass. This type of chondrosarcoma can have a variable appearance on imaging, with the lesion appearing lytic, permeative, or even sclerotic. Deep endosteal scalloping is often visible. Other common features include cortical thickening, aggressive periostitis, and an associated soft tissue mass. A chondroid matrix, identified by arcs and whorls, may be present. On MRI, intramedullary chondrosarcoma is isointense to muscle on T1-weighted images (indicating marrow replacement) and hyperintense (often lobulated) on T2-weighted images.

Juxtacortical/periosteal chondrosarcoma is a periosteal lesion that causes cortical erosion, leading to saucerization. In fact, it can look similar to periosteal osteosarcoma except there is no "hair on end" periostitis. This lesion may spare the intramedullary canal. A chondroid matrix is a common feature.

Clear cell chondrosarcoma is distinct from the intramedullary form in a number of ways. It typically affects a younger age group, has a better prognosis, and is most commonly (>90%) an epiphyseal lesion. This preference for the epiphysis, combined with the presence of a chondroid matrix (33% of cases), is one way that clear cell chondrosarcoma can mimic chondroblastoma. But because 50% of these lesions are completely lytic, clear cell chondrosarcoma can also mimic a giant cell tumor. One way to differentiate these lesions is the presence of very high T2 signal; neither chondroblastoma nor giant cell tumor will display high T2 signal.

Mesenchymal chondrosarcoma is an aggressive, high grade lesion. It typically affects a younger age group than the intramedullary form, with an average age of 25 years. With this tumor, the chondroid matrix is less prominent and the soft tissue mass more common than in the intramedullary form. Mesenchymal chondrosarcoma can be extraskeletal, and may arise in the meninges or thigh. These extraskeletal manifestations have a poor prognosis.

Myxoid chondrosarcoma is more aggressive than the intramedullary form and has a less favorable prognosis. The name comes from this lesion’s myxoid appearance on imaging, which is derived from its high water content. As one might expect, the signal is very high on T2-weighted images (similar to the urinary bladder) and low on T1-weighted images. These lesions can also be extraskeletal, most commonly arising in the thigh or popliteal fossa. Extraskeletal manifestations are less aggressive in this form and typically affect middle-aged patients (average age: 50 years).

Dedifferentiated chondrosarcoma typically affects an older age group, with an average age of 60 years. This is a high grade tumor with a spindle cell component. It is often a secondary chondrosarcoma. On imaging, the chondroid matrix is usually absent, while a soft tissue mass is very common.

Difficulty Level: 4th Year

References

Weissleder R, Reiumont MJ, Wittenberg J, Primer of Diagnostic Imaging 2nd Ed. St. Louis: Mosby, 1997.

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