A chordoma is a rare type of cancerous tumor that can occur anywhere along the spine, from the base of the skull to the tailbone. Chordomasgrow slowly, gradually extending into the bone and soft tissue around them. A small number of families have been reported in which multiple relatives have been affected by chordoma. In four of these families duplication of the brachyury gene was found to be responsible for causing chordoma.
In one study, the 10-year tumor free survival rate for sacral chordoma was 46%. Chondroid chordomas appear to have a more indolent clinical course. In Norway, the annual incidence of chordoma is approximately 0.8 in one million.
There are three histological variants of chordoma: conventional, chondroid and dedifferentiated. The histological appearance of classical chordoma is of a lobulated tumor composed of groups of cells separated by fibrous septa. The cells have small round nuclei and abundant vacuolated cytoplasm, sometimes described as physaliferous (having bubbles or vacuoles). Chondroid chordomas histologically show features of both chordoma and chondrosarcoma.
There are currently no known genetic or environmental risk factors for chordoma. While most people with chordoma have no other family members with the disease, rare occurrences of multiple cases within families have been documented. This suggests that some people may be genetically predisposed to develop chordoma. Because genetic or hereditary risk factors for chordoma may exist, scientists at the National Cancer Institute are conducting a Familial Chordoma Study to search for genes involved in the development of this tumor.