The patient went on to have submucosal nasopharyngeal biopsies.

Histology: 

The section contains skeletal muscle fibers, which are infiltrated by a malignant spindle cell tumor.  The tumor forms diffuse sheets and vague short fascicles.  These tumor cells show moderately pleomorphic and angulated nuclei with hyperchromasia, granular chromatin, inconspicuous nucleoli and ill-defined scanty cytoplasm. Scattered mitoses are seen.  There are also amorphous strands of focally calcified, eosinophilic material in the stroma. No staghorn blood vessels are seen. The spindled tumor cells are CD99 positive. They are EMA, AE1/3, CD34, S-100 and SMA negative.

There is chondroid matrix, containing atypical chondrocytes, in keeping with a chondrosarcoma. The cytokeratin stain is negative, excluding a carcinoma. The presence of CD99 positive spindle cells suggests mesenchymal chondrosarcoma. However, the amount of these spindled cells is small and not all the classic features of mesenchymal chondrosarcoma are seen on histology.  Alternatively, the spindle cell areas may represent dedifferentiation.

Final diagnosis:   high-grade chondrosarcoma.