Sacrococcygeal teratomas arise from the primitive knot or Hensen"s node. Hensen"s node is an aggregation of totipotential cells that are the primary organizers of embryonic development. Originally located in the posterior portion of the embryo, it migrates caudally during the first weeks of life inside the tail of the embryo, finally resting anterior to the coccyx. Segregation of totipotential cells from Hensen"s node probably gives rise to sacrococcygeal teratomas . These pluripotential cells escape from the control of embryonic inducers and organizers and differentiate into tissues not usually found in the sacrococcygeal region . The tumor occurs near the coccyx, where the greatest concentration of primitive cells exists for the longest period of time during development.
The most common prenatal clinical presentation of sacrococcygeal teratoma is uterus size greater than dates . However, the majority of cases usually manifest no clinical symptoms during pregnancy and with the increasing frequency of routine ultrasound during pregnancy, more incidental findings of these tumors will occur. The differential diagnosis of sacrococcygeal teratomas include myelomeningoceles, lipomas, hydromyelia, intracanalicular epidermoid tumors, dermal sinus stalks, extrarenal Wilms" tumors, retrorectal hamartomas, neuroblastomas, and pacinomas . Excluding meningomyelocele and twin fetuses, a mass attached to the fetal rump is most likely a teratoma . A sacrococcygeal teratoma can be distinguished from its primary differential meningomyelocele by its more abundant internal soft tissue, whereas the meningocele is more completely cystic in nature . Alpha-Fetoprotein can be normal or elevated in sacrococcygeal teratomas, but sonography can distinguish these lesions from neural tube defects . Early prenatal sonographic detection of sacrococcygeal teratoma allows for optimal perinatal obstetric and surgical management.
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