Sacrococcygeal teratoma (SCT) is the most frequently encountered tumor in newborn infants, occurring in approximately one in 35,000 to 40,000 live births. This congenital mass develops at the base of the spine, originating near the coccyx, or tailbone. SCT is a type of germ cell tumor, meaning it arises from cells that can differentiate into multiple tissue types. The visibility and potential size of the tumor often make it a prominent concern for families and medical professionals.
Defining Sacrococcygeal Teratomas and Their Origin
A teratoma is a tumor derived from pluripotent germ cells that can mature into tissues representing all three primary embryonic germ layers. These layers are the ectoderm (skin and neural tissue), the mesoderm (muscle, bone, and connective tissue), and the endoderm (lining of the digestive and respiratory systems). Consequently, an SCT can be composed of a disorganized mixture of tissues like hair, bone, cartilage, and glandular epithelia.
The location of SCTs is rooted in early embryonic development, specifically the primitive streak and Hensen’s node in the sacrococcygeal region. These structures contain totipotent cells that can be retained and undergo disorganized growth. The resulting tumor is classified based on the maturity of its cellular components. Most SCTs found at birth (around 75%) are mature teratomas, which are benign. Others are immature teratomas or contain malignant elements, such as yolk sac tumor components.
Categorizing SCTs: The Altman Classification System
The Altman classification system is the standard method used to categorize sacrococcygeal teratomas based on their anatomical location and degree of intrapelvic extension. This classification predicts the complexity of surgical removal and the potential for long-term functional issues. The system divides tumors into four distinct types, defined by the tumor mass’s relationship to the infant’s pelvis.
Type I
These are the most common, accounting for nearly half of all cases. They are predominantly external with only a minimal component extending into the presacral space.
Type II
These tumors have a significant external mass but also possess a distinct intrapelvic component extending into the lower pelvis. This internal extension often gives the tumor a “dumbbell” shape, requiring a more complex surgical approach.
Type III
These tumors are predominantly internal, extending significantly into the pelvis and often into the abdomen, while retaining a visible external component. They pose a higher risk of complications due to the pressure exerted on abdominal and pelvic organs.
Type IV
These are the least common and are entirely presacral, or internal, with no visible external presentation. Their internal location makes them difficult to detect without imaging, often resulting in a delayed diagnosis and symptoms from compression of pelvic structures.
Diagnosis and Monitoring During Pregnancy
SCTs are frequently identified prenatally during routine ultrasound screening, which improves outcomes. Ultrasound allows clinicians to assess the tumor’s size, consistency (solid, cystic, or mixed), and vascularity (blood flow). Serial ultrasound examinations monitor tumor growth and detect associated complications throughout the pregnancy.
Fetal Magnetic Resonance Imaging (MRI) provides a precise anatomical map of the tumor’s extent, helping determine the Altman classification. MRI delineates the relationship of the internal mass to the pelvic organs and the spine, which is crucial for planning delivery and postnatal surgery. Monitoring also focuses on the risk of high-output cardiac failure in the fetus.
Large or highly vascular tumors can shunt a significant portion of the fetal blood supply, forcing the heart to work harder. This can lead to non-immune hydrops fetalis, a severe condition characterized by fluid accumulation in two or more fetal body cavities, associated with a poor prognosis. Polyhydramnios, an excessive accumulation of amniotic fluid, is also monitored as it can be caused by the tumor or high blood flow.
Alpha-fetoprotein (AFP) is a protein produced by the fetal liver and yolk sac, serving as a biomarker for SCT. Elevated AFP levels in maternal serum and amniotic fluid can indicate the presence of an SCT. High or rapidly rising levels suggest a greater risk of malignancy or a rapidly growing tumor. Postnatally, AFP monitoring continues as part of the long-term surveillance protocol.
Postnatal Surgical Management and Long-Term Follow-Up
The definitive treatment for nearly all SCTs is complete surgical excision, regardless of size or appearance. Postnatal surgery is often performed within the first few days of life, especially for large tumors, to prevent complications like rupture, hemorrhage, or malignant degeneration. The surgical approach is tailored to the Altman classification, sometimes requiring a combined abdominal and sacral approach for internal Type III and Type IV tumors.
A fundamental aspect of the surgical technique is the complete removal of the coccyx (tailbone) along with the tumor mass. The tumor is believed to arise from totipotent cell remnants embedded in the coccyx, and leaving the bone increases the risk of local tumor recurrence. Pathology examination determines if the tumor is mature, immature, or contains malignant components. If malignant elements are found, the infant requires additional treatment, typically chemotherapy, following the initial surgery.
Long-term follow-up focuses on detecting recurrence and managing potential functional deficits. Serial monitoring of serum AFP levels is performed for several years post-surgery, usually monthly for the first year. A rise in AFP can be the first sign of recurrence, particularly if the original tumor was immature or malignant. Recurrence rates are significantly higher if the tumor was initially malignant or if the coccyx was not removed during the primary operation.
Survivors of SCT, particularly those with higher Altman types (III and IV) or large internal tumors, require careful monitoring for neurogenic bowel and bladder dysfunction. The extensive surgery or pressure from the original tumor can affect the nerves controlling these functions. Management of these functional outcomes may involve bowel regimens, medications, or specialized urological procedures.