The patient went on to have surgery.

Histology

MICROSCOPIC DESCRIPTION: The sections show an epithelioid tumor, forming cords and nests, embedded in prominently myxomatous stroma. The tumor invades into bony trabeculae in the medulla. The tumor cells have mildly enlarged and hyperchromatic ovoid nuclei, small nucleoli and moderate amounts of eosinophilic cytoplasm. Scattered physaliferous cells are seen and they show cytoplasmic vacuolation. Lymphovascular invasion is absent. The tumor cells are CAM5.2 positive. The Ki-67 index is about 2%. S-100 and M2A are negative. The features are those of chordoma.

FINAL DIAGNOSIS: Chordoma.

Discussion

Although most chordomas have more bony destruction than this lesion, the direct posterior direction of growth and relatively high T2 signal are common features.