Abnormal sacrum morphology Teratoma Sacrococcygeal teratoma 2016-03-13T09:57:33Z UMLS:C0559459 Sacrococcygeal teratomas arise from totipotent cells from the node of Hensen at the anterior aspect of the coccyx by about the 2nd to 3rd weeks of gestation, and are composed of the all three germ cells (i.e. ectoderm, mesoderm and endoderm). Sacrococcygeal teratomas are classified according to their relative extent outside and inside the body. Altman type I: entirely outside, sometimes attached to the body only by a narrow stalk; Altman type II: mostly outside; Altman type III: mostly inside; Altman type IV: entirely inside. A teratoma arising in the sacro-coccygeal region. SNOMEDCT_US:281561000