Chondromyxoid Fibroma of the Sacral Spine.

Background and Importance. Chondromyxoid fibromas are rare tumors of cartilaginous origin typically found in long bones. They usually present during the second and third decades of life. In this case report, we describe the case of a 60-year-old male who presented with back pain and was later found to have a sacral mass. Further immunohistochemical analysis determined that the mass was a chondromyxoid fibroma. Clinical Presentation. A 60-year-old male presented with worsening lower back pain over the course of 2 years. Magnetic resonance imaging demonstrated a destructive mass centered at S4 with heterogeneous enhancement. The patient underwent an S3-to-Co1 laminectomy for gross total resection of the tumor. Histology demonstrated a biphasic, lobulated appearance, characteristic of a chondromyxoid fibroma. The tissue stained faintly positive for multicytokeratin, and it was negative for markers S-100 protein and brachyury, indicating that it was not a chordoma. Conclusion. Only 8 cases have documented sacral chondromyxoid fibroma. As these are exceedingly rare tumors, especially within the sacral spine, the differential diagnosis includes other malignant tumors more likely to be found in the spine, particularly chordomas and chondrosarcomas. Immunohistochemistry and histology are essential in making a definitive diagnosis. This case provides a comprehensive illustration of the clinical presentation, radiographic findings, and immunohistochemistry of sacral chondromyxoid fibroma.