What is the recommended approach for prenatal detection, evaluation, and management of fetal tumors?

Fetal Tumors: Prenatal Detection, Evaluation, and Management

Prenatal Detection and Initial Evaluation

Ultrasound is the primary screening and diagnostic modality for detecting fetal tumors, with fetal MRI without gadolinium serving as the essential complementary study for characterization, risk stratification, and delivery planning. 1, 2, 3

Imaging Protocol

• Ultrasound remains the first-line imaging method for initial detection and ongoing surveillance of fetal tumors throughout pregnancy 2, 4
• Fetal MRI without gadolinium should be performed when ultrasound findings are inconclusive or when detailed anatomic characterization is needed for management decisions 5, 1, 3
• Avoid gadolinium-based contrast agents entirely, as gadolinium crosses the placenta and has been associated with increased risk of stillbirth, neonatal death, and rheumatologic conditions in offspring 5, 6, 7
• CT scans should be avoided throughout pregnancy for fetal tumor evaluation, as ultrasound and MRI provide superior soft tissue characterization without ionizing radiation 5

Specific MRI Advantages by Tumor Type

MRI provides critical diagnostic information that directly impacts perinatal management:

• Sacrococcygeal teratomas: Diffusion-weighted and T1-weighted MRI reliably predict tumor morphology and composition, which is essential for risk stratification 3
• Head and neck tumors: MRI is superior to ultrasound for assessing airway compromise and planning delivery strategy, including potential EXIT (ex utero intrapartum treatment) procedures 3
• Cardiac rhabdomyomas: MRI can detect specific brain alterations associated with tuberous sclerosis from the early third trimester onwards, regardless of tumor number or size on ultrasound 3
• Abdominal tumors: MRI enhances diagnostic accuracy and characterizes the lesion's relationship to surrounding anatomic structures 1

Common Fetal Tumor Types

Most Frequently Encountered Tumors

The most common fetal tumors include 1, 8:

• Teratomas (sacrococcygeal, cervical, mediastinal)
• Cardiac rhabdomyomas
• Mesoblastic nephroma
• Neuroblastoma
• Hepatoblastoma
• Nephroblastoma (Wilms' tumor)

Abdominal Cystic Lesions (Non-Neoplastic)

Common cystic lesions that require differentiation from true neoplasms include 1:

• Ovarian cysts
• Choledochal cysts
• Intestinal duplication cysts
• Mesenteric cysts
• Simple hepatic cysts
• Meconium pseudocysts

Multidisciplinary Management Approach

All pregnancies with diagnosed fetal tumors should be managed at tertiary centers with expertise in fetal medicine, pediatric surgery, and neonatal intensive care. 1, 8

Essential Team Composition

The care team must include 5:

• Maternal-fetal medicine specialist
• Neonatologist
• Pediatric surgeon or surgical subspecialist
• Pediatric oncologist (when malignancy is suspected)
• Obstetric anesthesiologist

High-Risk Pregnancy Monitoring

These pregnancies require designation as high-risk with regular fetal monitoring 5:

• Serial ultrasound examinations to assess tumor growth and development of complications
• Monitoring for polyhydramnios, hydrops fetalis, and placentomegaly (indicators of high-output cardiac failure)
• Assessment for maternal mirror syndrome in cases of fetal hydrops

Indications for Fetal Intervention

Fetal intervention or surgery is rarely indicated but should be considered in specific circumstances 1, 8:

Sacrococcygeal Teratoma

In utero intervention may be necessary when:

• High-output cardiac failure develops due to tumor vascularity
• Hydrops fetalis is present or imminent
• Rapid tumor growth threatens fetal viability before lung maturity

Intervention options include 8:

• Minimally invasive procedures (radiofrequency ablation, laser coagulation of feeding vessels)
• Open fetal surgery for tumor debulking (extremely rare)

Other Tumors

Most other fetal tumors do not require prenatal intervention and are managed with optimized timing and location of delivery 1, 8

Delivery Planning

Accurate prenatal diagnosis permits optimization of delivery timing, mode, and location to facilitate immediate postnatal management. 1, 2

Timing of Delivery

Target full-term delivery (≥37 weeks) whenever possible 5:

• Early delivery (34-37 weeks) should be discouraged unless maternal or fetal health is endangered
• Very early delivery (<34 weeks) is associated with worse neurodevelopmental outcomes

Mode and Location of Delivery

Delivery should occur at a tertiary center with:

• Immediate availability of pediatric surgical and oncology expertise 1
• Neonatal intensive care unit capabilities
• Potential for EXIT procedure if airway obstruction is anticipated (head/neck tumors) 3

Cesarean delivery may be indicated for:

• Large tumors that may cause dystocia
• Risk of tumor rupture during vaginal delivery (particularly sacrococcygeal teratomas)
• Anticipated need for immediate surgical intervention

Prognosis and Long-Term Outcomes

The majority of prenatally diagnosed tumors have good prognosis with current multimodality treatment 1, but outcomes vary significantly by tumor type.

Survival and Morbidity Data

In a large single-center cohort over 20 years 3:

• 22% of pregnancies were terminated
• 15% of continuing pregnancies resulted in fetal or neonatal death
• Among survivors, 53% were healthy, 18% had minor illness, and 29% had serious long-term illness

This high rate of serious morbidity among survivors underscores the importance of:

• Accurate prenatal counseling about long-term outcomes
• Comprehensive postnatal follow-up
• Early intervention for developmental concerns

Critical Pitfalls to Avoid

Common errors in fetal tumor management include:

• Delaying MRI evaluation: When ultrasound findings are concerning, MRI should be performed promptly to guide management decisions 3
• Using gadolinium contrast: This is contraindicated due to fetal risks; non-contrast MRI provides excellent tissue characterization 5, 6
• Underestimating airway risk: Head and neck tumors require detailed MRI assessment and delivery planning with potential EXIT procedure 3
• Assuming cardiac rhabdomyomas are isolated: These require MRI brain evaluation for tuberous sclerosis regardless of tumor characteristics on ultrasound 3
• Delivering at non-tertiary centers: Immediate access to specialized surgical and neonatal care is essential for optimal outcomes 1

Postnatal Management

Immediate postnatal evaluation should include 1:

• Physical examination by pediatric surgeon
• Appropriate imaging (ultrasound, MRI, or CT as indicated)
• Histopathological examination of resected tumors
• Placental histological examination (particularly important for melanoma, though rare in fetal cases) 5

Long-term follow-up is essential given the significant rate of serious morbidity among survivors, including monitoring for tumor recurrence, developmental assessment, and management of associated syndromes 3