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Dedifferentiated Chondrosarcoma

Summary

Dedifferentiated chondrosarcoma is a high-grade sarcoma that develops in a preexisting benign cartilage tumor, or in a preexisting low / intermediate grade chondrosarcoma. The tumor is a spindle cell sarcoma, most commonly osteosarcoma or malignant fibrous histiocytoma. The low grade and high grade portion are adjacent but distinct. Prognosis is poor.

Complete Information on this Tumor
Introduction and Definition: 

Dedifferentiated chondrosarcoma is a distinct form of chondrosarcoma where a high-grade sarcoma is found adjacent to a low grade chondrosarcoma. This aggressive tumor is associated with a poor prognosis. Five-year survival is from 0 to 20% approximately.

Incidence and Demographics: 
This form of chondrosarcoma is relatively rare, data must be gathered from an aggregate of case series. Slightly more men than women are affected. Typical patients range in age from 30 to 100 years, with the peak age at diagnosis being approximately 70 to 75. The tumor can present in a variety of bones, the most common location is the proximal and distal followed by the pelvis. Other common locations include the proximal humerus, the scapula, and the tibia.
Symptoms and Presentation: 

Patients typically present with pain and a mass. Approximately 90% of patients present with pain. The aggressive nature of the sarcoma is typically reflected by rapid growth, a pathological fracture, or severe and increasing pain. Approximately 12% of patients have pathologic fracture.

X-Ray Appearance and Advanced Imaging Findings: 
The x-ray findings typically present an aggressive bone lesion, with destructive pattern of growth, situated in an intramedullary location. The image may reflect a permeated pattern of growth with the lesion infiltrating normal bone before destroying it. The low-grade portion of the lesion has a narrow margin of transition with a less aggressive appearance, the hygrade portion of the lesion typically is less calcified, more lytic and destructive, with a wider zone of transition. There is typically extraosseous extension of the aggressive portion of the lesion. Intralesional calcifications are typically seen in the low-grade portion of the lesion.
Differential Diagnosis: 
The differential includes other sarcomas such as fibrosarcoma, malignant fibrous histiocytoma, and others.
Preferred Biopsy Technique for this Tumor: 
Open incisional.
Histopathology findings: 
Dedifferentiated chondrosarcoma is a cartilage forming neoplasm with an area of low grade juxtaposed with an area of high-grade sarcoma. The high-grade areas are poorly differentiated and may have little or no resemblance to cartilage. The high-grade areas may have a spindle cell appearance, and may resemble malignant fibrous histiocytoma, osteosarcoma, and other sarcomas. Osteosarcoma is the most common diagnosis of the high-grade area.
Treatment Options for this Tumor: 
Surgery is the cornerstone of treatment for this sarcoma. Basic orthopedic oncologic principles are used in planning surgical therapy. Some patients who present with overwhelming disease are best managed with palliative care. Younger and healthier patients are typically managed with multiagent chemotherapy, typically including Adriamycin, ifosfamide, methotrexate, or a combination, but no established protocol of chemotherapy treatment has been established for this tumor.
Preferred Margin for this Tumor: 
I wide margin is preferred.Radical margins have been recommended but the benefit of radical margin has not been firmly established. The influence of margin on outcome is not yet defined.
Outcomes of Treatment and Prognosis: 
Despite treatment, the outcome for this tumor remains poor. In one series, the overall five-year survival rate was just 7.1%, and in another five-year survival was just 13%. Median survival is approximately 7.5 months. No definite benefit of chemotherapy has been shown. No definite benefit of treatment of pulmonary metastasis has been shown. In one series, disease free survival was not improved by chemotherapy.
Special and Unusual Features: 
The juxtaposition of the low-grade and high grade portions of the lesion, often easily distinguished on x-rays and on MRIs, is the hallmark of this lesion.
Suggested Reading and Reference: 
Dedifferentiated Chondrosarcoma: The Role of Chemotherapy with Updated Outcomes Ian D. Dickey, MD1; Peter S. Rose, MD1; Bruno Fuchs, MD, PhD1; Lester E. Wold, MD1; Scott H. Okuno, MD1; Franklin H. Sim, MD1; Sean P. Scully, MD, PhD2 The Journal of Bone & Joint Surgery. 2004; 86:2412-2418