Chordomas are very rare primary bone tumors that can arise at
almost any point along the axis of the spine from the base of
the skull to the sacrum and coccyx (tailbone). The incidence of
chordoma in the general U.S. population is about 8 per
10,000,000 people. They occur somewhat more often in males than
females and, for unknown reasons, are rare in African Americans.
Under the microscope, chordoma cells appear to be benign, but
because of their location, invasive nature, and recurrence rate,
the tumors are considered to be malignant. They arise from
cellular remnants of the primitive notochord, which is present
in the early embryo. In normal mammalian development, the
notochord and substances produced by it are involved in forming
the tissues that give rise to vertebrae. Normally, the tissues
derived from the notochord disappear after the vertebral bodies
have begun forming. However, in a small percentage of people,
some tissues from the notochord do not disappear. Rarely, these
leftover tissues give rise t