Paraffin sections show fragments of a densely hypercellular tumour. Tumour cells have small round hyperchromatic nuclei and a large amount of vacuolated cytoplasm imparting a physalliferous appearance. Tumour cells are arranged in solid aggregates and cords within a mucinous stroma. Tumour cells show strong immunostaining for cytokeratin CAM5.2 and weaker staining for S100 protein. The features are of chordoma.
FINAL DIAGNOSIS: Chordoma.