Instructional Course Lectures, The American Academy of Orthopaedic Surgeons - Chondrosarcoma

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Chondrosarcoma is a malignant tumor of cartilage-producing cells35. It is subdivided in a variety of ways, including by histological grade, by whether it is primary or secondary, and by whether it is peripheral or central; among these, the single most prognostic sub-classification is the histological grade. In addition, there are a few specific histological subtypes of chondrosarcoma: clear-cell, mesenchymal, base of the skull, and soft-parts chondrosarcoma. Chondrosarcoma is most often separated into three histological grades: low (grade 1), medium (grade 2), and high (grade 3). The higher the grade, the more likely it is that the tumor will metastasize. Grading is based on the tumor's histological appearance, with tumors that most resemble normal cartilage being low-grade (grade 1) and having the least risk of metastasizing, and those that have the most abnormal-appearing cartilage being high-grade (grade 3) and having a higher risk of metastasizing (Figs. 1 and 2). A type of chondrosarcoma that has a higher risk of metastasizing than a grade-3 chondrosarcoma is the uncommon, so-called dedifferentiated chondrosarcoma7,24. This chondrosarcoma is believed to arise from a benign cartilage lesion or a low-grade chondrosarcoma. On histological examination, it has areas of malignant spindle cells that cannot be recognized as being of cartilaginous origin, adjacent to areas of neoplastic chondrocytes surrounded by a hyaline-cartilage matrix. The dedifferentiated chondrosarcoma is the most malignant of the chondrosarcomas and has an extremely high risk of distant metastasis. A review of the experience at the Mayo Clinic with dedifferentiated chondrosarcoma found that only eight of seventy-eight patients who had such a lesion survived for more than five years after the initial diagnosis12. This finding is consistent with the four and five-year survival rates reported in other studies3,8. Photomicrograph of a low-grade chondrosarcoma. The …