The growth patterns of sacral chordomas were studied in 4 cases by MRI before surgery. The size of the tumor in each patient was 6×6×6cm, 6×9×7cm, 9×7×6cm and 11×16×14cm, respectively. As the tumors increased in size, the structure of the sacrum was destroyed aggressively, and muscles such as gluteus maximus, piriformis and coccygeus were involved irregularly. However, only slight tumor invasion into the sacral spinal canal was seen in all cases. The rectal wall or the sacro-iliac joints were never involved. These results indicated that the growth patterns of sacral chordomas differed dependent upon the specific tissue surrounding the tumors.
