Chondrosarcoma of the posterior fossa--case report.

The authors describe a case of well differentiated (grade I) chondrosarcoma in a 52-year-old male. The tumor originated in the posteromedial wall of the left petrous bone and extended into the posterior fossa and cervical spine. He showed impaired functions of the left VII to XII cranial nerves. Plain skull x-rays demonstrated erosion of the left petrous and occipital bones, with speckled calcifications. Computed tomography showed a huge mass of slightly high density with mushroom-like calcifications, which was poorly enhanced by contrast medium. Inversion recovery magnetic resonance imaging clearly defined the low-intensity lesion, while the long spin-echo image depicted the tumor as mixed-intensity. On electron microscopic examination, the tumor cells were rich in Golgi apparatus, endoplasmic reticulum, glycogen granules and mitochondria in the cytoplasm, and formed many vacuoles crossing the cell membrane. These vacuoles were suggested to play an important role in matrix formation. Thirty nine other reported cases of chondrosarcoma are reviewed, and the two reported posterior fossa chondrosarcomas are compared with that of ours.