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Extraosseous osteosarcoma of the lung

Two cases of extraosseous osteosarcoma of the lungs are described and 3 cases previously reported in the literature are reviewed. All tumors were large, fleshy, osteoid masses occupying the hilar and central areas of the lungs. In 4, there were metastases in lymph nodes and viscera. The tumors in our patients appeared to be rapidly growing; they attained a size of 6 and 7 cm in greatest diameter, respectively, within a few months, and the patients developed symptoms related to pneumonitis. Both tumors were highly cellular, composed of fibrosarcoma and poorly differentiated mesenchymal tissue with formation of osteoid and immature and malignant cartilage and bone in variable quantity. The pathogenesis of this very rare neoplasm and its classification are discussed.