Papanicolaou stained smear of a clival chordoma, microscopy. Chordomas are cancers formed of cells which resemble those of the notochord (spine) of a developing foetus. Although they can present anywhere within the spine and skull, the majority grow in the sacral region of the spine, corresponding to the lower back. This image shows a Papanicolaou (Pap) stained smear obtained from a needle biopsy of a chordoma in the clivus, a part of the cranium at the base of the skull.

Chordomas are relatively benign in the sense that they grow slowly and do not metastasize (spread to other parts of the body). However, their relentless growth with compression of the spinal cord often causes considerable problems with the adjacent nerves, brain and spine. They can be recognized in fine needle biopsy samples by characteristic large cells with vacuoles (bubbles) in their cytoplasm called physaliferous cells which grow in lobules (lumps). In this image, the vacuoles can be clearly seen in the pale blue cytoplasm of the cells, the nuclei of which are stained purple, amongst a background of myxoid (mucous-like) material. Horizontal image width 336 micrometres