A comparative ultrastructural study of chondrosarcoma, chordoid sarcoma, and chordoma.

: A morphologic and electron microscopic study was made of two chordoid sarcomas. These lesions were compared with two classical chondrosarcomas and two chordomas. These chondrosarcoma cells showed many features common to chondrocytes, such as abundant RER, well-developed Golgi complexes, and microvillous cytoplasmatic membranes. The chordoid sarcomas bore a close morphologic resemblance to the chordomas but the ultrastructural features revealed a close relationship to the chondrosarcomas. The chordoid sarcoma and chondrosarcoma cells had scalloped cytoplasmatic membranes, variable amounts of glycogen, round or oval nuclei and microfibrils, collagen, and electron-dense granules in the ground substance. The chordoma was characterized by the presence of stellate and physalipherous cells, as well as many transitional cells, with varying nuclear morphology; dilated and irregular RER in contact with mitochondria and morphologically varied vacuoles are the main features in the cytoplasm. This study suggests that chordoid sarcoma represents a variety of the chondrosarcoma rather than a form of chordoma. These findings also support the suggestion of Weiss that chordoid sarcoma is an extraskeletal myxoid chondrosarcoma.