Primary Spinal Dumbbell-Shaped Mesenchymal Chondrosarcoma: A Case Report and Review of the Literature.

We report a rare case of a dumbbell-shaped mesenchymal chondrosarcoma (MCS) in the lumbar canal. A 29-year-old man presented with lower back pain and pain in the left leg. Magnetic resonance imaging (MRI) showed a homogeneously enhanced dumbbell-shaped mass at the left L2-3 level. The mass was intradurally located and extended extradurally into the extraforaminal space through the left L2-3 intervertebral foramen. Computed tomography (CT) showed a calcified portion in the intradural mass. We exposed and excised the tumor via a posterior approach through a hemi-laminectomy of the left L2-3. The tumor had penetrated the dura mater and required repair. Following surgery, his symptoms resolved completely. The most likely histopathological diagnosis was MCS. Histologic examination of our surgical samples revealed the typical biphasic pattern, but there was also cartilage matrix resembling osteoid. Finally, molecular assays confirmed the presence of the HEY1::NCOA2 fusion gene. Although spinal intradural extramedullary MCS is rare, only a few reports in the literature mention spinal dumbbell-shaped MCS. Following the removal of dumbbell-shaped MCS, the dura mater may require repair. While histopathological evaluation remains the gold standard for confirming a diagnosis of MCS, the HEY1::NCOA2 fusion gene is a specific molecular marker for MCS, and the presence of this gene has become a powerful tool for diagnosis.