OBJECTIVETo study the clinicopathologic and radiologic features of dedifferentiated chondrosarcoma, focusing on its diagnosis and differential diagnosis.

METHODClinical, radiological and pathologic findings of 14 cases of dedifferentiated chondrosarcoma (including biopsy and surgical specimens) were analyzed by hematoxylin and eosin stained sections and immunohistochemistry.

RESULTSThe mean age of patients was 52 years. The male-to-female ratio was 9:5. The most common sites of involvement were pelvis, femur and humerus, similar to the conventional chondrosarcoma. Radiologically, they were malignant tumors with dimorphic pattern. Grossly, central chondrosarcomas were more common than those of the peripheral. An essential histological feature of dedifferentiated chondrosarcoma was an abrupt interface between the low-grade cartilaginous tumor and high-grade anaplastic sarcoma. The most common dedifferentiated components were osteosarcoma, malignant fibrous histocytoma and fibrosarcoma. False negative diagnosis and erroneous diagnosis were frequent when only one-time biopsy was available.

CONCLUSIONSDedifferentiated chondrosarcoma is a rare subtype of chondrosarcoma with poor prognosis, which has different features of clinical manifestation, imaging features and pathological characteristics, compared to conventional chondrosarcoma and chondroblastic osteosarcoma.