Microtubule aggregates in a clival chordoma.

We report a case of a clival chordoma in a 21-year-old man that ultrastructurally demonstrated large numbers of microtubule aggregates within the rough endoplasmic reticulum. Histologically, the tumor demonstrated classic chordoma architecture characterized by numerous physaliphorous cells and an abundant extracellular matrix. The tumor cells stained strongly for cytokeratin, S100 protein, and epithelial membrane antigen, indicative of the epithelial origin of this tumor. Ultrastructurally, the most conspicuous feature of this tumor consisted of parallel bundles of criss-crossing microtubules within the rough endoplasmic reticulum. These microtubules had a diameter of approximately 27 nm and did not demonstrate an internal structure. To our knowledge, this is the first report of microtubule aggregates in a spheno-occipital chordoma. We note that microtubule aggregates have been described in a number of different entities, and though proposed as a specific feature of "chondroid chordoma," they are a nonspecific finding.