Background: Dedifferentiated chondrosarcomas that arise in
osteochondromas are extremely rare lesions for which very little information
on treatment and outcome is available in the literature. The purpose of the
present study was to describe the specific clinical, radiographic, and
histologic features of this lesion and to evaluate the oncologic outcome after
different treatment strategies.
Methods: We reviewed the files of the Rizzoli Institute between 1970
and 2002 and identified eighteen patients for whom adequate records and
histologic images were available and in whom a high-grade sarcoma had been
diagnosed at the same location as a preexisting osteochondroma. Radiographic
studies, histologic slides, and clinical records were reviewed, the features
of those studies were tabulated, and prognostic features and the results of
treatment were identified.
Results: The patients included twelve men and six women with an
average age of forty-six years (range, twenty-two to seventy-four years).
Eight lesions occurred in patients with multiple osteochondromas, and ten
occurred in patients with solitary lesions. The most common locations were the
pelvis (six lesions) and the femur (five lesions). Symptoms included pain,
swelling, and a growing mass; the average duration of symptoms was eighteen
months. Radiographically, ten lesions appeared as a conventional secondary
chondrosarcoma arising in an exostosis, whereas eight showed typical signs of
dedifferentiation. Histologic evaluation of the cartilage component
demonstrated thirteen grade-1 and two grade-2 chondrosarcomas. In three cases,
no cartilage component was recognized. The dedifferentiated component was
considered to be an osteosarcoma in nine cases (including six cases in which
it was osteoblastic and three in which it was fibroblastic), a malignant
fibrous histiocytoma in eight, and a fibrosarcoma in one. The dedifferentiated
component represented an average of 59% (range, 20% to 100%) of the lesion.
For the fifteen patients who were managed at the authors' institution, the two
and five-year survival rates were 47% and 29%, respectively; the median
survival time was fourteen months. Patients who were managed with a
combination of surgery and chemotherapy had a better overall survival rate
than did those who were managed with surgery alone (p = 0.03).
Conclusions: Dedifferentiated chondrosarcoma arising in a
preexisting osteochondroma is an extremely rare lesion with a poor prognosis.
In the present small series, overall survival was better when wide surgical
resection was combined with adjuvant chemotherapy.
Level of Evidence: Therapeutic Level IV. See Instructions
to Authors for a complete description of levels of evidence.