Developmental abnormalities in the embryo may lead to tumours in the sacro-coccygeal area, so-called sacral cysts and the teratomas (5, 7). At birth they are caudal tumours of variable size covered with thin, stretched skin. Blood vessels can be seen through the skin, particularly in the mid-line. One gains the impression that the stretched skin could burst at any moment. It is assumed that these teratomas derive from the pluripotent cells of Hensen's node and then grow in front of the coccyx (2). They grow and spread in various directions, particularly in a dorsal and caudal direction extra-rectally and, to a lesser extent, into the pelvis in a pre-sacral position. The classification of these tumours depends on their spread. The spread and localisation of these tumours may cause stenosis of elongation of the rectum and displacement of small and large bowel and of the bladder.