[MRI: an essential examen for the management of sacrococcygeal chondromas].

Chordomas are rare tumors, involving mainly the sacrococcygeal area and the clivus. Although a significant radiological semiology exists (osteolytic, lobulated, calcified tumor), the definite diagnosis is histological. Five cases of sacral and/or coccygeal chordomas were studied by CT scan and MRI. Clinical, radiological (tumoral topography and extension) and histological data were noted in all cases. At CT scan, the tumor was median, osteolytic, often calcified, of intermediate density, sparing iliac bones. MRI showed, in all the cases, a tumoral lobulation making easier the diagnosis of chordoma. Futhermore, as compared to CT scan MRI brought new information for the study of the tumoral extension, revealing a frequent involvement of adjacent muscles and spinal canal. It also showed that the tumor most often spared the rectal wall. These data are fundamental in the management of patients: the therapeutical aim must be, if possible, a complete removal of the tumor. Thus, besides its interest in the diagnosis, MRI appears to be essential in the pre-therapeutical assessment of sacro-coccygeal chordomas.