Sacrococcygeal teratomas are rare tumors that develop at the base of the spine by the tailbone (coccyx) known as the sacrococcygeal region. Although most of these tumors are non-cancerous (benign), they may grow quite large and once diagnosed, always require surgical removal. It is likely that all sacrococcygeal teratomas are present at birth (congenital) and most are discovered before birth by a routine prenatal ultrasound examination or an exam indicated for a uterus too large for dates. In rare cases, sacrococcygeal teratomas may be cancerous (malignant) at birth and many will become malignant if surgical resection is not performed. In extremely rare cases, sacrococcygeal tumors may be seen in adults. Most of these represent slow growing tumors that originated prenatally. In the majority of these cases, the tumor is benign, but may cause lower back pain and genitourinary and gastrointestinal symptoms. The cause of sacrococcygeal teratomas is unknown.
The symptoms that occur with sacrococcygeal teratomas vary widely depending upon the size and specific location of the tumor. Small tumors often do not cause any symptoms (asymptomatic) and can usually be removed surgically after birth without difficulty.
However, larger sacrococcygeal tumors can cause a variety of complications before and after birth. Sacrococcygeal teratomas can grow rapidly in the fetus and require very high blood flow resulting in fetal heart failure, a condition known as hydrops. This is manifest as dilation of the heart, and the collection of fluid in tissues of the body, including the skin and body cavities such as around the lungs (pleural effusion), around the heart (pericardial effusion), and/or in the abdominal cavity (ascites). If neglected, hydrops can also be dangerous for the mother resulting similar symptoms of swelling, hypertension, and fluid on the lungs with shortness of breath. In addition to hydrops, which can occur in approximately 15% of very large fetal sacrococcygeal teratomas, these tumors can cause polyhydramnios (too much amniotic fluid), fetal urinary obstruction (hydronephrosis), bleeding into the tumor or rupture of the tumor with bleeding into the amniotic space, or dystocia (a condition where the fetus cannot be delivered due to the size of the tumor. It is very important to have very close monitoring during pregnancy to recognize these symptoms as early as possible.
In adults, sacrococcygeal teratomas may not cause symptoms (asymptomatic). In some cases, they may cause progressive lower back pain, weakness, and abnormalities due to obstruction of the genitourinary and gastrointestinal tracts. Such symptoms include constipation and increased frequency of stools or urinary tract infections. In rare cases, sacrococcygeal tumors cause partial paralysis (paresis) of the legs and tingling or numbness (paresthesia).
The cause of sacrococcygeal teratomas is unknown. Sacrococcygeal teratomas are germ cell tumors. Germ cells are the cells that develop into the embryo and later on become the cells that make up the reproductive system of men and women. Most germ cell tumors occur in the testes or ovaries (gonads) or the lower back. When these tumors occur outside of the gonads, they are known as extragonadal tumors. Researchers do not know how extragonadal germ cell tumors form. One theory suggests that germ cells accidentally migrate during to unusual locations early during the development of the embryo (embryogenesis). Normally, such misplaced germ cells degenerate and die, but in cases of extragonadal teratomas researchers speculate that these cells continue to undergo mitosis, the process where cells divide and multiply, eventually forming a teratoma.
Sacrococcygeal teratomas are thought to arise from an area under the coccyx called “Henson’s Node”. This is an area where primitive cells persist (germ cells) that can give rise to cells of the three major tissue layers of an embryo: ectoderm, endoderm, and mesoderm. These embryonic layers eventually give rise to the various cells and structures of the body. Sacrococcygeal teratomas can contain mature tissue that looks like any tissue in the body, or immature tissue resembling embryonic tissues.
Sacrococcygeal teratomas occur in females more often than males by a 4:1 ratio. Malignancy is more common in males. The prevalence of these tumors is estimated to be between 1 in 30,000-70,000 live births. Sacrococcygeal teratomas are the most common solid tumor found in newborn babies (neonates). The sacrococcygeal region is the most common site for a teratoma in infants. Sacrococcygeal teratomas affecting adults is extremely rare. Adults cases often represent tumors that were present at birth (congenital), but not detected until adulthood.
In most cases, sacrococcygeal teratomas are diagnosed at birth when a large tumor is detected protruding from the sacral region. Many sacrococcygeal teratomas are found incidentally on routine prenatal ultrasounds or they may be detected on an ultrasound that is obtained because the uterus is too large for the stage of pregnancy due to the bulk of the tumor, or accumulation of amniotic fluid. During an ultrasound, reflected sound waves create an image of the developing fetus. Even small sacrococcygeal teratomas may be visible on an ultrasound picture.
In some cases, a sample of the amniotic fluid or maternal serum may be taken and studied to determine the levels of alpha-fetoprotein (AFP). AFP is a normal fetal plasma protein that when elevated may indicate the presence of certain conditions such as a sacrococcygeal teratoma.
If a sacrococcygeal teratoma is diagnosed prenatally a careful examination is usually done to rule out other anomalies. In some institutions a fetal MRI scan is also performed to better delineate the anatomy of the tumor and displaced structures. For large sacrococcygeal teratomas, very frequent ultrasounds and echocardiograms (to measure the size of the cardiac chambers and blood flows) are required to monitor for signs of evolving hydrops. During an echocardiogram, reflected sound waves are used to take pictures of the heart. It is extremely important that a medical team experienced with large fetal sacrococcygeal teratoma follows the pregnancy. All fetuses with large sacrococcygeal teratomas need delivery by a “classical” cesarean section (large incision in the uterus) to avoid tumor rupture and hemorrhage at the time of delivery. Most fetuses with large tumors are born premature and need expert perinatal care from a multidisciplinary team.
In adults, a diagnosis of sacrococcygeal teratoma may be suspected during a routine pelvic or rectal examination that detects the presence of a mass or tumor. A diagnosis of sacrococcygeal teratoma may be confirmed by surgical removal and microscopic examination of affected tissue (biopsy). One procedure is known as fine needle aspiration, in which a thin, hollow needle is passed though the skin and inserted into the nodule or mass to withdraw small samples of tissue for study.
In addition to an ultrasound, other specialized imaging techniques may be used to diagnose a tumor as well as evaluate the size, placement, and extension of the tumor and to serve as an aid for future surgical procedures. After birth, such imaging techniques may include computerized tomography (CT) scanning and magnetic resonance imaging (MRI). During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of certain tissue structures. An MRI uses a magnetic field and radio waves to produce cross-sectional images of particular organs and bodily tissues. In cases of malignant sacrococcygeal teratomas, laboratory tests and specialized imaging tests may also be conducted to determine possible infiltration of regional lymph nodes and the presence of distant metastases.
When an individual is diagnosed with a sacrococcygeal teratoma, assessment is also required to determine the extent or “stage” of the disease. Staging is important to help characterize the potential disease course and determine appropriate treatment approaches. Certain of the same diagnostic tests described above may be used in staging.
Sacrococcygeal teratomas are classified according to the American Academy of Pediatrics Surgical Section:
Type I – the tumor is predominantly external with a very minimal internal component. Type I is rarely associated with malignancy.
Type II – the tumor is predominantly external but has some internal extension into the presacral space.
Type III – the tumor is visible externally, but is predominantly located in the pelvic area with some extension into the abdomen.
Type IV – the tumor is not visible externally and is located in the presacral space. Type IV has the highest rate of malignancy.
The initial management of a fetus with a sacrococcygeal teratoma requires the coordinated efforts of a perinatal team of medical professionals such as maternal fetal medicine physicians to deliver the infant, and pediatric surgeons and neonatologists to resect the tumor and manage the medical issues of the infant who can sometimes be critically ill. All prenatally diagnosed sacrococcygeal teratomas require resection during the neonatal
period and if the tumor is large, as quickly as possible to avoid rupture of the tumor. Resection always involves resection of the tumor along with the coccyx. Failure to resect the coccyx is associated with a 30% local recurrence rate of the tumor. This can usually be done from the back of the neonate but for some tumors with extensive extension into the pelvis and abdomen, an abdominal incision must also be performed. Most children that undergo early resection of sacrococcygeal teratomas ultimately do well with a very low incidence of malignant or benign tumor recurrance, and normal urogenital, bowel, and lower extremity neurologic function. These children are usually followed by the pediatric surgeon by rectal examinations and interval serum AFP levels to monitor for recurrence for 3 years before they are considered cured with no possibility of tumor recurrence.
In rare instances where malignancy is diagnosed by the pathologist after resection a team of medical professionals who specialize in the diagnosis and treatment of cancer (medical oncologists) will need to be consulted. Specific therapeutic procedures and interventions may vary, depending upon numerous factors, such as primary tumor location and corresponding complications; extent of the primary tumor (stage); whether it has spread to lymph nodes or distant sites; an individual's age and general health; and/or other elements. Decisions concerning the use of particular interventions should be made by physicians and other members of the health care team in careful consultation with the patient or parents, based upon the specifics of the case; a thorough discussion of the potential benefits and risks; and other appropriate factors.
In rare cases, complications resulting from a sacrococcygeal teratoma may necessitate intervention before birth (prenatally). Interventions such as tapping the amniotic fluid (amniocentesis) to reduce the volume and delay the onset of preterm labor may be required. If the tumor has hemorrhaged and the fetus is anemic, a fetal blood transfusion may be helpful. Occasionally, an obstructed fetal urinary tract will need to be treated by a vesicoamniotic shunt (a catheter between the bladder and amniotic fluid) to relieve the obstruction and prevent damage to the kidneys. In rare cases when the fetus is documented to be in the early stages of hydrops, open fetal surgery may be required (surgery on the fetus in the womb) to “debulk” the tumor and reduce the demand for blood flow. After removal of the bulk of the tumor, the fetus is returned to the womb so that the hydrops can improve prior to birth. Although this has been successful about 50% of the time, it is a major undertaking and extensive consideration of the risks to the mother is appropriate. Although radio frequency ablation (a technique where a needle is inserted into the tumor and radiofrequency energy is applied to the tumor to destroy blood flow) has been reported, all survivors have had complications of damage to the genitourinary system so this approach is considered highly experimental.
In adults, surgical removal of the entire tumor and the tailbone (coccyx) is the main treatment option. Removal of the coccyx lowers the chance of recurrence. For benign tumors surgical removal of the tumor is usually sufficient. However, for malignant tumors, affected individuals should receive additional treatment with chemotherapy and radiation therapy.
Because malignant sacrococcygeal teratomas are extremely rare, especially in adults, no standard chemotherapeutic regimen or radiation therapy has been established.
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