Astrocytoma is a neoplasm of the central nervous system derived from astrocytes. Astrocytes are a type of glial cell, and thus astrocytoma is a subtype of glioma.

Chordomas are rare, clinically malignant tumors derived from notochordal remnants. They occur along the length of the spinal axis, predominantly in the sphenooccipital, vertebral, and sacrococcygeal regions. They are characterized by slow growth, local destruction of bone, extension into adjacent soft tissues, and, rarely, distant metastatic spread (Stepanek et al., 1998). The incidence of chordoma is age-dependent, with fewer than 5% occurring in children and adolescents (summary by McMaster et al., 2011).