[46] Dedifferentiated Chondrosarcoma with Low Grade Dedifferentiated Component – A Single Instituitional Study.

Meera R Hameed, John Healey, Carol Morris, Patrick Boland, Michael J Klein. Memorial Sloan-Ketetring Cancer Center, New York, NY; Memorial Sloan-Kettering Cancer Center, NewYork, NY; Hospital for Special Surgery, NewYork, NY

Background: Dedifferentiated chondrosarcoma is a highly malignant sarcoma composed of two divergent histologies, a low-grade cartilaginous component and a high-grade noncartilaginous sarcomatous component. Typically, the low-grade component is a grade 1 chondrosarcoma and the high-grade component is an anaplastic sarcoma such as an osteosarcoma or undifferentiated pleomorphic sarcoma. This tumor usually affects patients over 50 years and most commonly occurs in long bones; it is highly lethal with less than 10% survival after 1 year. Generally the dedifferentiated component is resistant to chemotherapy and radiation therapy. Dedifferentiation to a low grade mesenchymal component such as low grade osteosarcoma or fibrosarcoma is extremely rare.
Design: The objective of this study was a retrospective review of dedifferentiated chondrosarcomas from 1984-2009 from Pathology Department of MSKCC files to identify cases with low-grade dedifferentiation and to correlate pathological findings with outcome. Materials and Methods: Following IRB approval and SNOMED search, thirty four cases with available slides, resected at MSKCC were identified.
Results: There were 19 males and 15 females. Patient age group ranged from 21 to 96 years. Location of the tumor is as follows: femur (19), pelvis (9), humerus (3), scapula (2) and chest wall (1). Tumor size ranged from 2.3 cm to 27 cm. Tumor was confined within bone in 3 out of 34 cases. In a majority of cases (76%), the chondrosarcomatous component was grade II or I-II. The dedifferentiated component consisted of either a high grade spindle cell sarcoma or a pleomorphic undifferentiated sarcoma in 24 out of 34 cases (70%). The remainder were pleomorphic sarcoma and osteosarcoma (5), osteosarcoma (4) and fibrosarcoma (1). In addition, 7 cases (20%) had areas of low grade spindle cell dedifferentiation comprising about <5% to 80% of the dedifferentiated component. Follow up was available for 26 patients (1.5-46 months). Sixteen patients were dead and ten are alive, two with metastatic disease. In this group, three of four patients with areas of low grade dedifferentiation are alive (11-33 months).
Conclusions: Low grade dedifferentiation can be seen in dedifferentiated chondrosarcoma. Awareness of this phenomenon is important especially in biopsy specimens. Rarely this histology can be predominant.
Category: Bone & Soft Tissue

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 6, Tuesday Morning


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