[Primary malignant mesenchymoma of the lung]

A case of a primary malignant mesenchymoma of the lung with elements of rhabdomyo-, leiomyo-, osteo-, fibro- and lipo-sarcoma is described. The tumor developed in a man of 58 with a long history of smoking, complaints of chest pains and cough with scanty sputum expectoration. The neoplastic process involved the upper lobe of the left lung and microscopically contained smooth muscle, endothelial, fibroblast-like cells, multinuclear giant cells resembling osteoclasts, strips of osteoid-like hyalinized connective tissue. Electron-microscopic examination revealed myoid-type cells with clusters of myofilaments and Z-type material, cells resembling fibroblasts, osteoclasts and lipocytes. It is suggested that there should be a common histogenesis of primary lung sarcomas arising from a stem cell precursor of mesenchymal origin in lung stroma, bronchial and vascular walls, pleura.