An emergency decompressive craniectomy of the right fronto t

An emergency decompressive craniectomy of the right fronto-temporo-parietal region was performed, and an external ventricular drain was placed. The tumor was dark-brown, lobulated, and hypervascular. The interface between cyclosporin and tumor was well defined. The tumor and its dural attachment were totally removed (Fig. 2B). Two days after the first operation, decompressive craniectomy was performed contralaterally because of persistently elevated intracranial pressure. In pathological study, the tumor was light tan to dark brown and contained foci of oval-shaped bony tissue grossly. Microscopically, there were many small vascular spaces, some with a staghorn pattern. The tumor was composed of sheets of small, undifferentiated, oval or spindle-shaped cells and islets of cartilaginous tissue with foci of central calcification and ossification (Fig. 3). Mitoses were rare. Areas of necrosis were found. The dimorphic pattern and the presence of necrosis were consistent with a diagnosis of mesenchymal chondrosarcoma. In spite of all our efforts, the patient did not regain consciousness and remained in a vegetative state postoperatively. The patient was brought back three years after the first operation with bulging of the scalp flap at the right craniectomy site. Brain CT revealed local recurrence of the tumor in the right middle cranial fossa (Fig. 4). Because of her persistent vegetative state, the family refused further surgery and other treatment modalities.
Discussion Intracranial mesenchymal chondrosarcoma was initially thought to arise from bone. However, in nearly half of reported cases it was extraskeletal, with the meninges being the most common site of origin. Hypotheses about the pathogenesis posit an origin in embryonal cartilaginous rests in the skull and dura or from meningeal fibroblasts or multipotent mesenchymal cells in the dura or arachnoid, but the evidence available is inadequate to draw a firm conclusion. As noted above, mesenchymal chondrosarcomas have two basic components. The tumors are highly cellular with undifferentiated mesenchymal cells, but they also contain islands of well-differentiated hyaline cartilage. The undifferentiated cells have round to spindle-shaped nuclei and are randomly arranged in sheets surrounding the cartilage. This appearance contrasts with classical chondrosarcoma, in which cells are usually well-differentiated with few or no mesenchymal components. Instead, the cartilaginous element predominates and gradually merges with the stroma. The microscopic distinction between classical and mesenchymal chondrosarcoma is thus not difficult. Although the arrangement of undifferentiated cells of mesenchymal chondrosarcoma closely resembles that of hemangiopericytoma, the presence of cartilaginous foci is sufficient to exclude hemangiopericytoma. If light microscopic features are equivocal, ultrastructural examination may be useful in delineating these two entities. In our case, the light microscopic findings were quite clear and sufficient to confirm the diagnosis of mesenchymal chondrosarcoma. A few years after mesenchymal chondrosarcoma of non-osseous origin was first described, Dahlin and Henderson reported the first case of one occurring intracranially. Since then, 39 cases have been reported, the largest single series being that of Rushing et al in 1996 with eight intracranial tumors. Including our case, the 40 patients’ ages have ranged from 6 months to 68 years (mean 21.2 years), including 19 who were 15 years old or less. The male-to-female ratio was 9:11, and the peak incidence was in the second and third decades. This differs from classical chondrosarcoma, with a male-to-female ratio of 5:3 and a peak incidence in the sixth decade. The tumor was attached to the dura in 31 patients, including ours, and was intraparenchymal in the other nine patients. The high proportion of cases with dural involvement lends support to the theory that the tumor originates in multipotent mesenchymal cells in the dura or arachnoid. The outcome varied considerably, with 17 patients dying 3 days to 9 years (mean 39.7 months) after surgery. The longest reported survival was 10 years, and that patient died of a myocardial infarction. Recurrences occurred in 18 patients, ranging from 3 weeks to 3 years after resection. One patient developed leptomeningeal dissemination, and 3 had distant metastases to the vertebrae, ribs, or heart and intra-abdominal organs. The wide range in reported outcome seems to indicate considerable variability in the natural history of the disease. Of all the reported cases, ours is the only one with uncal herniation occurring before surgery.