Hyaline cartilage is prone to calcification, a process in which calcium phosphate crystals become embedded in the tumors characterized by secretion of cartilage matrix. Ap-proximately 3.6% of primary bone tumors that are diagnosed in the United States each year are chondrosarcomas. These tumors are the second most common matrix-producing tu-mors of bone after osteosarcomas (malignant bone-forming tumors). They occur more commonly in men than women and affect individuals that are usually age 45 and older. Chondrosarcomas originate predominantly in the axial skele-ton (and most commonly involve vertebrae, pelvic bones, ribs, scapulae, and the sternum), and in metaphyses of prox-imal ends of long bones (most often the femur and humerus). The most common symptom reported by patients is a deep pain, often present for months and typically dull in character. Since cartilaginous tissue is compressed inside the bone, in most cases initial growth of a tumor cannot be palpated. Radiographs, CT, and MRI scans are essential for the initial diagnosis and later for the evaluation of the extent of deep intramedullary tumors. Chondrosarcomas are classified by grades that strongly correlate with a patient’s prognosis. Micro-scopically, grade 1 represents the least aggressive and grade 3 represents the most aggressive tumor. Most chondrosarcomas (90%) are pathologically classified as conventional (grades 1 and 2); they rarely metastasize and are composed of hyaline cartilage that infiltrates bone marrow cavity and surrounds existing bony trabe-culae (Fig. F7.2.1). Multiple chondroblasts that are often binucleated with pleomorphic and hyperchromatic nu-clear patterns are frequently seen in a single lacuna. Cartilaginous matrix may also undergo mineralization and subsequent endochondral ossification. Metastatic spread to lungs and lymph nodes is more frequently asso-ciated with grade 3 lesions. Recently, immunohistochemical localization of collagen types has been used to determine stage of tissue differenti-ation, which in fact correlates with a patient’s prognosis. The presence of collagen types II and X and the proteogly-can aggrecan in biopsies indicates mature tumors associ-ated with good prognosis. On the other hand, the presence of collagen type I indicates changes in the extracellular ma-trix toward dedifferentiated (fibrous) types of tumor with poorer prognosis. In addition, transcription factor SOX9, which is essential for differentiation of mesenchymal cells into chondroblasts during normal fetal development, is expressed in chondrosarcomas. Treatment of chondrosarcoma is primary surgical: The tumor is widely excised. Chemotherapy and radiation play limited roles in treatment. Patients with adequately re-sected low-grade tumors have an excellent survival rate. FIGURE F7.2.1 • Photomicrograph of a chondrosarcoma (grade 1) from the epiphysis of the long bone, stained with H&E. This photomicrograph shows a tissue mass of chondrosarcoma infiltrating intertrabecular spaces of the bone marrow. Note the presence of malignant chondrocytes in various stages of maturity. Small area of active bone marrow is visible in the upper left corner of the image. 240. (Courtesy of Dr. Fabiola Medeiros.) marrowmarrowmarrowbonebonebonechondrosarcomachondrosarcomachondrosarcoma  FOLDER 7.2 Clinical Correlation: Malignant Tumors of the Cartilage; Chondrosarcomas
Chondrosarcomas are generally slow-growing malignant cartilage matrix. The matrix of hyaline cartilage undergoes calcification as a regular occurrence in three well-defined situations:  The portion of articular cartilage that is in contact with bone tissue in growing and adult bones, but not the surface portion, is calcified.