As the tumor grows, it can push between other organs and through the perineum to the body surface where the tumor appears as a bulge covered only by skin. Sometimes, the tumor bulge later slips back inside the perineum. Like all teratomas, a sacrococcygeal teratoma has the potential to be malignant, and the standard of care requires long-term followup by an oncologist. Management of fetal SCTs
Management of most fetal SCTs involves watchful waiting prior to any treatment. An often used decision tree is as follows:

Perform detailed ultrasound exam including fetal echocardiogram and Doppler flow analysis
If fetal high output failure, placentomegaly, or hydrops
If fetus not mature, perform pregnancy termination or fetal intervention
Else fetus mature, perform emergency Cesarean section
Else no emergent problems, perform serial non-stress tests and ultrasound biophysical profiles and plan delivery, as follows
If emergent problems develop, return to top of decision tree
Else if SCT over 5–10 cm or polyhydramnios, perform early (37 weeks gestation) elective Cesarean section
Else SCT small and no complications, permit term spontaneous vaginal deliveryEmergent problems include maternal mirror syndrome, polyhydramnios, and preterm labor. Poor management decisions, including interventions that are either premature or delayed, can have dire consequences. A very small retrospective study of 9 babies with SCTs greater than 10 cm diameter reported slightly higher survivorship in babies remaining in utero slightly longer.In many cases, a fetus with a small SCT (under 5 or 10 cm) may be delivered vaginally. Prior to the advent of prenatal detection and hence scheduled C-section, 90% of babies diagnosed with SCT were born full term.
Other tumors can occur in the sacrococcygeal and/or presacral regions and hence must be ruled out to obtain a differential diagnosis. These include extraspinal ependymoma, ependymoblastoma, neuroblastoma and rhabdomyosarcoma. Smaller SCTs with an external component, seen in prenatal ultrasounds or at birth, often are mistaken for spina bifida. Cystic SCT and terminal myelocystocele are especially difficult to distinguish;  for more accurate diagnosis, MRI has been recommended. Treatment
The preferred first treatment for SCT is complete surgical removal (i.e., complete resection). The preferred approach to a small SCT is through the perineum; a large SCT may require an additional approach through the abdomen. Resection should include the coccyx and may also include portions of the sacrum. The surgery should include reattachment of the small muscles and ligaments formerly attached to the coccyx, in effect reconstructing the posterior perineum. If not, there is an increased risk of perineal hernia later in life. SCTs are classified morphologically 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;  this is also known as a presacral teratoma or retrorectal teratomaThe Altman type is significant in the contexts of management of labor and delivery, surgical approach, and complications of SCT. Serial ultrasound and MRI monitoring of SCTs in fetuses in utero has demonstrated that the Altman type can change over time.