Papanicolaou stained smear of a C2 vertebral chordomal mass, 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 of the C2 vertebrae, located at the top of the neck just underneath the base of the skull.