[A case of intracranial mesenchymal chondrosarcoma--changes observed by computed tomography before and after radiotherapy (author's transl)].

Intracranial mesenchymal chondrosarcoma is very rare, only 14 cases being reported in Europe and in the United States of America. Recently we experienced a case in which the follow-up indicating computed tomograms (CT) demonstrated interesting data on the radiosensitivity of this tumor. The patient, a 14-year-old female was admitted to out hospital with the complaint of left hemiplegia which had gradually progressed. CT revealed an area spreading upward from the right median base of the skull and consisted of two components showing (A) a density as high as that of calcium and (B) a density higher than that of surrounding brain tissue, but much lower than that of calcium. Temporoparietal craniotomy was performed to react approximately one-half of the tumor. Histological finding revealed mesenchymal chondrosarcoma. The component-A was though to be a cartilaginous tissue, and-B to be an undifferentiated mesenchymal tissue. Postoperative irradiation of 7,000 rad was initiated. The effect of radiotherapy as seen on computed tomograms is as follows, (1) decrease in the volume of the tumor by 26%, (2) decrease in density and enhancement of the area which is considered to be the undifferentiated mesenchymal cells, (3) mild reduction of the area which is considered to be the cartilaginous tissue, and (4) a very high density of the entire tumor similar in degree to that of the bone one year later. These results suggested that radiotherapy is effective for this tumor.